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WO2019060481A1 - Disilane-, carbodisilane-and oligosilane cleavage with cleavage compound acting as catalyst and hydrogenation source - Google Patents

Disilane-, carbodisilane-and oligosilane cleavage with cleavage compound acting as catalyst and hydrogenation source Download PDF

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WO2019060481A1
WO2019060481A1 PCT/US2018/051853 US2018051853W WO2019060481A1 WO 2019060481 A1 WO2019060481 A1 WO 2019060481A1 US 2018051853 W US2018051853 W US 2018051853W WO 2019060481 A1 WO2019060481 A1 WO 2019060481A1
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sime
mesi
group
cime
cleavage
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PCT/US2018/051853
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French (fr)
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Norbert Auner
Tobias SANTOWSKI
Alexander G. STURM
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Momentive Performance Materials Inc.
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Publication of WO2019060481A1 publication Critical patent/WO2019060481A1/en

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
    • C07F7/02—Silicon compounds
    • C07F7/08—Compounds having one or more C—Si linkages
    • C07F7/12—Organo silicon halides
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
    • C07F7/02—Silicon compounds
    • C07F7/08—Compounds having one or more C—Si linkages
    • C07F7/12—Organo silicon halides
    • C07F7/121—Preparation or treatment not provided for in C07F7/14, C07F7/16 or C07F7/20
    • C07F7/128—Preparation or treatment not provided for in C07F7/14, C07F7/16 or C07F7/20 by reactions covered by more than one of the groups C07F7/122 - C07F7/127 and of which the starting material is unknown or insufficiently determined

Definitions

  • the present invention relates to the technical field of the production of silane monomers, in particular to the production of mono-, di- and trimethylmonosilanes, starting from disilanes and oligosilanes by a cleavage reaction of the silicon-silicon bond, and from carbodisilanes by silicon-carbon bond cleavage, in each case in the presence of a cleavage compound and optionally a hydrogenation source.
  • Methylchlorosilanes and methylhydridosilanes are highly useful starting materials in synthetic organosilicon chemistry, and therefore constitute an industrially valuable class of compounds.
  • methylsilanes bearing both chloro- and hydrido substituents constitute attractive starting materials in synthesis due to their bifunctional nature, which means they have functional groups of different reactivities.
  • the chloride ligand is a better leaving group than the hydride group and allows, for instance, the controlled addition of further monomeric or oligomeric siloxane units with retention of the Si-H bond under mild conditions, thereby rendering said chlorohydridosilanes useful as blocking and coupling agents in the synthesis of defined oligo- and polysiloxanes.
  • Such compounds generally find a wide range of applications, for instance for the manufacture of adhesives, sealants, mouldings, composites and resins for example in the fields of electronics, automotive, construction and many more.
  • the Si-H moieties present in chlorosilanes can be utilized for postsynthesis modifications and functionalisations, for instance for the introduction of organic residues to polyorganosiloxanes or for cross-linking by hydrosilylation reactions, which is desirable in various kinds of compositions containing polyorganosiloxanes.
  • Synthesis of functionalized polysiloxanes starting with transformations via the Si-H bond(s) followed by hydrolysis or alcoholysis of the Si-CI bond(s) and optionally condensation for the formation of polysiloxanes is also viable.
  • US 5175329A describes a process wherein a mixture of polysilanes and an organotrihalosilane are reacted with hydrogen gas in the presence of a hydrogenolysis catalyst, and a redistribution catalyst, at a temperature of 100° C to 400° C. In one run tetrabutylphosphonium chloride is used as redistribution catalyst. There is no pointer in US 5175329A according to that the redistribution catalyst would participate in the reaction. It is also unlikely that under the conditions of US 5175329A (hydrogen gas/pressure) the redistribution catalyst acts as a hydrogen donor. Moreover, the yields in Me 2 SiHCI are very low.
  • the problem to be solved by the present invention is the provision of a process for the production of monosilanes, in particular methylchloro- and methylhydridomonosilanes, and most preferred hydridosilanes, such as of Me 2 SiHCI in particular, by submitting disilanes, oligosilanes and carbodisilanes to cleavage conditions under which the desired products are obtained by Si-Si-bond cleavage, or by Si-C-bond cleavage in case of carbodisilanes acting as substrates.
  • the problem to be solved is in particular the provision of such an improved process in which high proportions of methylhydridomonosilanes and methylhydridochloromonosilanes with a high content of hydride substituents can be obtained.
  • the problem to be solved comprises the provision of a process by which monosilanes such as in particular Me 2 SiHCI, Me 2 SiH 2 , Me 3 SiCI, Me 2 SiCI 2 , Me 3 SiH, MeSiH 3 , MeSiHCI 2 , MeSiH 2 CI, and MeSiC can be obtained in high yield from silane substrates, in particular from the residue of the Muller-Rochow Direct Process, the so-called Direct Process Residue (DPR).
  • DPR Direct Process Residue
  • the present invention relates to a process for the production of monosilanes starting from disilanes, carbodisilanes, oligosilanes or mixtures thereof by cleavage of silicon-silicon bonds or carbon-silicon bonds, respectively, and to monosilanes produced by such process.
  • y 0 to 3, preferably 1 to 3, more preferably 1 or 2,
  • n 0 to 6, preferably 0 to 4,
  • each Si atom bears at least one methyl group
  • a, c are independently of each other 1 to 3,
  • b, d are independently from each other 0 to 2
  • e, f are independently from each other 0 to 2
  • cleavage compound selected from the group consisting of:
  • each R is independently a hydrogen or an organyl group
  • Q is phosphorus, arsenic, antimony or bismuth
  • X is a halide selected from the group consisting of F, CI, Br and I
  • the cleavage reaction of the silicon-silicon bond(s) and/or the silicon-carbon bond(s) in the silane substrate is preferably carried out in the presence of at least one compound which promotes such bond cleavage and acts as a hydride donor (cleavage compound).
  • (MeaSiHbCle)-CH 2 -(MecSiHdClf) (IV) can be depicted also by the structural formula: wherein the substituents R" are independently selected from methyl (Me), hydrogen (H) and chlorine (CI), and wherein the substituents R'" are independently selected from methyl (Me), hydrogen (H) and chlorine (CI), and wherein the number of methyl groups on each silicon atom (a, c) is independently from 1 to
  • the silane substrate is consisting of one or more silane substrate compounds selected from the group consisting of the disilanes of the general formula (II), linear or branched oligosilanes of the general formula (III) and the carbodisilanes of the general formula (IV).
  • the process of the present invention is characterized inter alia by any of the features (i) to (iii): (i) The process is run until at least about 50 mol-% of the cleavage compound based on the initial molar amount of the cleavage compound is reacted, and/or
  • reaction temperature and time are adjusted for a given silane substrate and a given cleavage compound so as to satisfy one or more of the conditions (i) to (iii) above, preferably condition (ii) and/or (iii) .
  • the process is run until at least about 50 mol-% of the cleavage compound based on the initial molar amount of the cleavage compound is reacted.
  • the process is run until the ratio of Me 2 SiHCI is at least about 20 mol-%, preferably at least about 30 mol-%, based on the total amount of the monosilanes of the general formula (I).
  • the process of the present invention it is possible that one of the features (i) to (iii) is adjusted, or that two of the features (i) to (iii) are adjusted or that preferably all of the features (i) to (iii) are adjusted.
  • the reaction in step A) is carried out for more than about 4 hours, preferably more than about 6 hours, and at a temperature of at least about 200 °C, or the reaction in step A) is carried out for more than about 10 hours preferably more than about 12 hours, at a temperature of more than about 100 °C, preferably more than about 150°C.
  • the process of the present invention is normally carried out without the supply of hydrogen (H 2 ). This advantageously also avoids the use of high pressure equipment since the process of the present invention can be usually carried out at normal pressure.
  • one compound of general formula (I) or a mixture of more than one compound of general formula (I) is formed. More preferably, mixtures of more than one compound of the formula (I) are formed.
  • the monosilanes of the general formula (I) formed in the process of the present invention include compounds selected from the group of: MeSiH 2 CI, Me 2 SiH 2 , Me 2 SiHCI, Me 3 SiH, Me 3 SiCI, MeSiHC , Me 2 SiCI 2 , MeSiC and MeSihh.
  • Such disilanes are in particular constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the methyldisilanes Me 3 Si-SiMe 2 CI, CIMe 2 Si-SiMe 2 CI, CI 2 MeSi-SiMeCI 2 , CIMe 2 Si-SiMeCI 2 , Me 3 Si-SiMeCI 2 , which are therefore preferred substrates in the process according to the invention.
  • DPR Direct Process Residue
  • Such disilanes are partially hydrogenated derivatives in particular of constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the methyldisilanes HMe 2 Si-SiMe 2 CI, H 2 MeSi-SiMeCIH, HCIMeSi-SiMeCIH, CIHMeSi-SiMeC , H 2 MeSi-SiMeCI 2 , HMe 2 Si-SiMeCI 2 , CIMe 2 Si-SiMeH 2 , HMe 2 Si-SiMeCIH, CIMe 2 Si-SiMeCIH and Me 3 Si-SiMeCIH.
  • DPR Direct Process Residue
  • Such disilanes are fully hydrogenated derivatives of in particular constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the methyldisilanes, HMe 2 Si-SiMe 2 H, H 2 MeSi-SiMeH 2 , HMe 2 Si-SiMeH 2 , Me 3 Si-SiMeH 2 and Me 3 Si-SiMe 2 H.
  • DPR Direct Process Residue
  • the one or more linear or branched oligosilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula formula (I II), wherein
  • each Si atom bears at least one methyl group
  • Such oligosilanes are constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, and include for example the methyloligosilanes CIMe 2 Si-SiMe 2 -SiMe 2 CI, CIMe 2 Si-SiMe 2 -SiMe 2 -SiMe 2 CI, (CIMe 2 Si) 3 SiMe, (CI 2 MeSi) 2 SiMeCI, (CI 2 MeSi) 3 SiMe, (CI 2 MeSi) 2 SiMe-SiCIMe-SiCI 2 Me, [(CI 2 MeSi) 2 SiMe] 2 , [(CI 2 MeSi) 2 SiMe] 2 SiCIMe,
  • Such oligosilanes are partially hydrogenated derivatives in particular of constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the methyloligosilane CIMe 2 Si-SiMe 2 SiMe 2 H.
  • Such oligosilanes are fully hydrogenated derivatives of constituents in particular of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the methyloligosilanes HMe 2 Si- SiMe 2 -SiMe 2 H, HMe 2 Si-SiMe 2 -SiMe 2 H, (HMe 2 Si) 3 SiMe, (H 2 MeSi) 2 SiMeH, (H 2 MeSi) 3 SiMe, (H 2 MeSi) 2 SiMe-SiHMe-SiH 2 Me, [(H 2 MeSi) 2 SiMe] 2 , [(H 2 MeSi) 2 SiMe] 2 SiHMe, (H 2 MeSi)
  • the one or more carbodisilanes subjected to the cleavage reaction of the silicon-carbon bonds linking the silyl groups with the methylene group are represented by the general formula (IV), wherein
  • a, c are independently of each other 1 to 3,
  • b, d are independently from each other 0 to 2
  • e, f are independently from each other 0 to 2
  • Such carbodisilanes are constituents of in particular the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the carbodisilanes CI 2 MeSi-CH 2 -SiMeCI 2 , CIMe 2 Si-CH 2 -SiMeCI 2 , CIMe 2 Si-CH 2 -SiMe 2 CI, Me 3 Si-CH 2 -SiMeCI 2 and Me 3 Si-CH 2 -SiMe 2 CI, and are therefore preferred substrates in the process according to the invention.
  • DPR Direct Process Residue
  • Such carbodisilanes are partially hydrogenated derivatives of constituents of in particular the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the carbodisilanes HCIMeSi-CH 2 -SiMeCIH, HMe 2 Si-CH 2 -SiMeCI 2 , HMe 2 Si-CH 2 - SiMe 2 CI, and Me 3 Si-CH 2 -SiMeCIH.
  • DPR Direct Process Residue
  • Such carbodisilanes are fully hydrogenated derivatives of constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the carbodisilanes H 2 MeSi-CH 2 -SiMeH 2 , HMe 2 Si-CH 2 -SiMeH 2 , HMe 2 Si-CH 2 -SiMe 2 H, Me 3 Si-CH 2 -SiMeH 2 , Me 3 Si-CH 2 -SiMe 2 H.
  • DPR Direct Process Residue
  • the substrates according to the general formulae (I I) , (I I I) and (IV) may be submitted to the conditions for cleavage reactions in step A) as single compounds represented by general formulae (I I), (II I) and (IV), as a mixture of compounds represented by general formulae (I I), (II I) and (IV) exclusively, or as mixtures comprising one or more compounds represented by general formulae (I I), (I I I), or (IV).
  • cleavage is the term used to describe the transformation by which disilanes represented by the general formula (I I) , oligosilanes represented by the general formula (I I I) and carbodisilanes represented by the general formula (IV) are reacted to produce monomeric silanes represented by the general formula (I).
  • the term "cleavage reaction of the silicon-silicon bond(s)" further indicates that according to the invention, the cleavage of the aforementioned substrates is effected by breaking the bond connecting the silicon atoms of these disilanes and oligosilanes.
  • the term "cleavage reaction of the silicon-carbon bonds" indicates that the cleavage reaction is effected by breaking one or both bonds between the silyl groups of the compounds and the methylene group linking the silyl groups.
  • Such cleavage processes comprise in particular hydrochlorination and hydrogenolysis reactions.
  • the optional step of separating the resulting monosilanes of the general formula (I) refers to any technical means applied to raise the content of one or more monosilanes according to the general formula (I) in a product mixture, or which results in the separation of single compounds of the formula (I) from a product mixture obtained in step A) of the process according to the invention.
  • step A) is carried out by subjecting the silane substrate to the cleavage reaction of the silicon-silicon bond(s) or the silicon-carbon bond(s) in the silane substrate in the presence of at least one compound (cleavage compound) selected from the group consisting of
  • each R is independently a hydrogen or an organyl group
  • Q is phosphorus, arsenic, antimony or bismuth
  • X is a halide selected from the group consisting of F (fluorine), CI (chlorine), Br (bromine) and I (iodine),
  • mixtures of a) heterocyclic amines and/or heterocyclic ammonium halides and b) quaternary Group 15 onium compounds R 4 QX are used.
  • the cleavage compound comprises about 0.01 weight percent to about 99.95 weight percent of a) heterocyclic amines and/or heterocyclic ammonium halides and from about 0.05 weight percent to about 99.9 weight percent of b) quaternary Group 15 onium compounds based on the total weight of components a) and b).
  • the cleavage compound contains about 5 wt% to about 85 wt% of 2- methylimidazole and about 95 wt% to about 15 wt% of tetra(n-butyl)-phosphonium chloride based on the total weight of the 2-methylimidazole and the tetra(n-butyl)-phosphonium chloride.
  • the weight ratio of a) the heterocyclic amines and/or the heterocyclic ammonium halides relative to b) the-quaternary Group 15 onium compounds is from about 1 :9 to about 9: 1 , more advantageously from about 1 :3 to about 3: 1 .
  • the molar ratio of the imidazole to the phosphonium chloride can be from about 1 .1 to about 100, specifically about 1 .5 to about 60 and more specifically about 1.5 to about 20.
  • an organyl group is any organic substituent group, regardless of functional type, having one free valence at a carbon atom.
  • the quaternary Group 15 onium compound R 4 QX is represented by the formula R 4 PCI wherein R is independently a hydrogen group or an organyl group, more preferably a hydrogen group, an aromatic group preferably having up to about 30 carbon atoms or an aliphatic hydrocarbon group preferably having up to about 30 carbon atoms.
  • R is independently a hydrogen or an alkyl, cycloalkyl, aryl or alkaryl group having from about 1 to about 30 carbon atoms, preferably about 2 to about 16 carbon atoms.
  • Preferred groups R include methyl, butyl such as n-butyl, iso-butyl, hexyl such as n- hexyl, tetradecyl, such as n-tetradecyl, octyl, such as n-octyl.
  • Particularly preferred examples of the quaternary 15 onium compound according to the invention are tetra(n-butyl)phosphonium chloride, tetra(n-butyl)phosphonium bromide, trihexyl(tetradecyl)phosphonium bromide, methyltri(isobutyl)phosphonium bromide, methyltri(isobutyl)phosphonium chloride, tetra(n-octyl)phosphonium chloride, tri(n- butyl)tetradecylphosphonium chloride, and octyltri(n-butyl)phosphonium chloride.
  • the heterocyclic amine according to the invention has at least one nitrogen atom in at least one 4- to 8-membered hydrocarbon ring, wherein the ring atoms adjacent to the nitrogen are carbon or nitrogen, and the hydrocarbon ring or rings are, independently of one another, aromatic or non-aromatic hydrocarbon rings.
  • the heterocyclic amine contains a five-membered ring with 1 to 3 nitrogen atoms.
  • the heterocyclic amine is imidazole or a substituted imidazole selected from the group consisting of 1 -methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2- isopropyl-imidazole, 4-methylimidazole, 2,4-dimethylimidazole, 2-(2-imidazolyl)imidazole, 2- phenylimidazole, imidazoline, imidazolidine, pyrazole, 3-methylpyrazole, pyrrolidone, N- methylpyrrolidone, 1 ,3-dimethyl-2-imidazolidone, 1 ,2,3-triazole, and 1 ,2,4-triazole.
  • the heterocyclic ammonium halide is derived from a heterocyclic amine having at least one nitrogen atom in at least one 4- to 8-membered hydrocarbon ring, wherein the ring atoms adjacent to the nitrogen are independently carbon or nitrogen atoms, and the hydrocarbon ring or rings are, independently of one another, aromatic or non-aromatic hydrocarbon rings, wherein the halide is fluoride, chloride, bromide.
  • the heterocyclic ammonium halide is derived from a heterocyclic amine with 1 to 3 nitrogen atoms in a five-membered ring , and the halide is fluoride, chloride, bromide or iodide.
  • the heterocyclic ammonium halide is 1 ,2-dimethyl-3-(n-propyl)- imidazolium chloride, 1 -ethyl-3-methylimidazolium bromide, 1 ,2-dimethyl-3-(n- butyl)imidazolium chloride, 1 -butyl-3-methyl-imidazolium chloride, 1 -(3-cyanopropyl)-3- methylimidazolium chloride, or 1 -methylimidazolium chloride.
  • the quaternary Group 15 onium compound is represented by the formula R 4 PCI, wherein R is independently a hydrogen group or an organyl group, more preferably a hydrogen group, an aliphatic hydrocarbon or an aromatic group.
  • R is independently a hydrogen or an alkyl, cycloalkyi, aryl or alkaryl group of about 1 to about 30 carbon atoms, preferably about 2 to about 16 carbon atoms.
  • R include methyl, butyl such as n-butyl, iso-butyl, hexyl such as n-hexyl, tetradecyl, such as n- tetradecyl, octyl, such as n-octyl as substituents.
  • Particularly preferred examples of the quaternary 15 onium compound according to the invention are tetra(n-butyl)phosphonium chloride, tetra(n-butyl)phosphonium bromide, trihexyl(tetradecyl)phosphonium bromide, methyltri(isobutyl)phosphonium bromide, methyltri(isobutyl)phosphonium chloride, tetra(n-octyl)phosphonium chloride, tri(n- butyl)tetradecylphosphonium chloride, and octyltri(butyl)phosphonium chloride.
  • the compounds of the formula R 4 PCI are formed in situ from compounds of the formulae R 3 P and RCI, wherein R is preferably an organyl group as defined above.
  • R represents independently a hydrogen or any organyl group as defined above. More preferably, R is independently a hydrogen or an alkyl, cycloalkyl, aryl or alkaryl group from about 1 to about 30 carbon atoms, preferably about 2 to about 16 carbon atoms.
  • This embodiment comprises in particular also that step A) of the process according to the invention which is carried out with a mixture of a phosphine R 3 P, wherein R is as defined above, such as n-Bu 3 P, and HX, preferably HCI, preferably in an ether solvent.
  • step A) is carried out by subjecting the silane substrates of the general formulae (I I) , (I I I) or (IV) or mixtures thereof to the cleavage reactions of step A) in the presence of a hydrogen halide HX, wherein X is selected from the group consisting of F, CI, Br and I .
  • the hydrogen halide is HCI.
  • step A) is carried out in the presence of at least one metal hydride, preferably at least one metal hydride selected from the group of alkali metal hydrides and alkaline earth metal hydrides, more preferably at least one alkali metal hydride, and most preferably lithium hydride.
  • at least one metal hydride preferably at least one metal hydride selected from the group of alkali metal hydrides and alkaline earth metal hydrides, more preferably at least one alkali metal hydride, and most preferably lithium hydride.
  • a hydrogenation reaction of the substrates of the general formulae (I I) , (I I I) and (IV) or of the products of the general formula (I) also takes place before, during or after the cleavage reaction of the substrates of the general formulae (I I), (I I I) and (IV) under the reaction conditions of step A) .
  • the term "hydrogenation” refers to the exchange of at least one chloro substituent of a compound by a hydrogen substituent by means of a hydride reagent.
  • one or more chloro substituents of at least one or more compounds of the general formulae (II), (III) or (IV) submitted to the reaction conditions of step A) are replaced by hydrogen substituents before or during the cleavage reaction by the presence of a metal hydride in reaction step A).
  • one or more chloro substituents of at least one or more monosilanes of the general formula (I) obtained in step A) or being part of the substrate mixture are replaced by hydrogen substituents before, during or after the cleavage reaction by the presence of a metal hydride in step A).
  • the silane substrate comprises at least one of the compounds selected from the group consisting of Si 2 CI 6 , C MeSi-SiMeCIH, HCIMeSi-SiMeCIH, CI 2 MeSi-SiMeH 2 , HCIMeSi-SiMeH 2 , CIMe 2 Si- SiMeCIH, CI 2 MeSi-SiMe 2 H, CIMe 2 Si-SiMeH 2 , HMe 2 Si-SiMeCIH, CIMe 2 Si-SiMe 2 CI, Me 3 Si- SiMe 2 CI, CIMe 2 Si-SiMe 2 H, Me 3 Si-SiMe 2 H, HMe 2 Si-SiMe 2 H, H 2 MeSi-SiMeH 2 , HMe 2 Si- SiMeH 2 , CI 2 MeSi-SiMeCI 2 , CIMe
  • the molar ratio of the cleavage compound used in step A) to the silane substrate compounds of the general formulae (II), (III) and (IV) is in the range of about 0.0001 to about 100 mol-%, more preferred 0.001 to 50 mol-%, more preferred 0.001 to 25 mol-%, even more preferred 0.01 to 10 mol- %, and most preferably 0.01 to 0.5 mol-% based on the molar amount of the silane substrate compounds.
  • the molar ratio is defined as n (cleavage reagent in step A)) / n (substrates of the general formulae (II), (III) and (IV) in step A).
  • the weight ratio of the cleavage compound used in step A) to the silane substrate compounds of the general formulae (II), (III) and (IV) is in the range of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 75 wt-%, more preferred about 0.1 to about 55 wt-%, even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% based on the total weight of the silane substrate.
  • the amount of the metal hydride in step A) in relation to the silane substrate is in the range of about 1 mol-% to about 600 mol-%, preferably about 1 to about 400 mol-%, more preferably about 1 to about 200 mol-%, most preferably about 25 to about 150 mol-%, based on the total molar amount of the chlorine atoms present in silane substrate compounds.
  • the molar ratio of the metal hydride in step A) to the chlorine atoms present in the methyldisilanes of the general formula (II), the oligosilanes (III), or the carbodisilanes of the general formula (IV), or mixtures thereof is in the range of about 1 to about 300 mol-%, more preferred about 10 to about 150 mol-%, even more preferred about 25 to about 100 mol-%, and most preferred about 25 to about 75 mol-% based on the total molar amount of the chlorine atoms present in silane substrate compounds.
  • the amount of the metal hydride in step A) in relation to the silane substrate is in the range of about 1 mol-% to about 400 mol-%, preferably about 1 to about 200 mol-%, more preferably about 1 to about 100 mol-%, most preferably about 25 to about 50 mol-%, based on the total molar amount of the silane substrate compounds.
  • the molar ratio is defined as n (metal hydride in step A)) / n (silane substrates of the general formulae (II), (II I) and (IV) in step A).
  • the silane substrates used in step A) are submitted to a hydrogenation step before the cleavage reaction of the silicon-silicon bond(s) is carried out, wherein chlorine atoms contained in the silane substrates are partially or completely exchanged by hydrogen atoms.
  • hydrogenation refers to the exchange of at least one chloro substituent of a compound by a hydrogen substituent by means of a hydride reagent.
  • one or more chloro substituents of at least one or more compounds of the general formulae (II), (I II) or (IV) which are later submitted to the reaction conditions of step A) are replaced by hydrogen substituents before these silane substrates are submitted to reaction step A).
  • the hydride reagent used in the hydrogenation step is selected from the group of metal hydrides and organometallic hydride reagents, such as diisobutyl aluminium hydride (DIBAL-H), tributyltin hydride (n-Bu 3 SnH) or sodium bis(2-methoxyethoxy) aluminumhydride.
  • DIBAL-H diisobutyl aluminium hydride
  • n-Bu 3 SnH tributyltin hydride
  • sodium bis(2-methoxyethoxy) aluminumhydride sodium bis(2-methoxyethoxy
  • metal hydrides in the sense of the present invention comprises complex metal hydrides, such as LiAIH 4 and NaBH 4 .
  • the hydride reagent used for the partial or complete reduction of substrate compounds of the general formulae (I I), (III) or (IV) is tributyltin hydride (n-Bu 3 SnH), even more preferably tributyltin hydride (n-Bu3SnH) in combination with tetraphenylphosphonium chloride (Ph 4 PCI) as catalyst, and most preferably tributyltin with Ph 4 PCI as catalyst in diglyme as solvent.
  • the hydrogenation of the silane substrates prior to step A) is carried out with a hydride donor selected from the group of metal hydrides, preferably complex metal hydrides and organometallic hydride reagents such as LiAIH 4 , n-Bu 3 SnH, NaBH 4 , / ' -BU 2 AIH or sodium bis(2-methoxyethoxy)aluminumhydride.
  • a hydride donor selected from the group of metal hydrides, preferably complex metal hydrides and organometallic hydride reagents such as LiAIH 4 , n-Bu 3 SnH, NaBH 4 , / ' -BU 2 AIH or sodium bis(2-methoxyethoxy)aluminumhydride.
  • hydride donor refers to any compound which is capable of donating at least one hydride anion used in a hydrogenation reaction of substrates of the general formulae (I), (II), (III) or (IV) which bear at least one chloro substituent.
  • metal hydride refers to any hydride donor containing at least one metal atom or metal ion.
  • complex metal hydrides refers to metal salts wherein the anions contain hydrides.
  • complex metal hydrides contain more than one type of metal or metalloid.
  • metalloid comprises the elements boron, silicon, germanium, arsenic, antimony, tellurium, carbon, aluminum, selenium, polonium, and astatine.
  • organometallic hydride reagent refers to compounds that contain bonds between carbon and metal atoms, and which are capable of donating at least one hydride anion used in a hydrogenation reaction of substrates of the general formulae (I), (II), (III) or (IV) which bear at least one chloro substituent.
  • step A) is carried out in the presence of an organic solvent, more preferably a high-boiling ether compound, even more preferably a high-boiling ether compound being diglyme or tetraglyme, most preferably diglyme.
  • organic solvent more preferably a high-boiling ether compound, even more preferably a high-boiling ether compound being diglyme or tetraglyme, most preferably diglyme.
  • the term "organic solvent” refers to any organic compound which is in liquid state at room temperature, and which is suitable as a medium for conducting the cleavage reactions of step A) therein. Accordingly, the organic solvent is preferably inert to the cleavage reagents according to present invention, and to hydrogenation reagents such as metal hydrides under reaction conditions. Furthermore, the starting materials of the general formulae (I I), (I I I) and (IV) and the products of the general formula (I) are preferably soluble in the organic solvent or fully miscible, respectively.
  • the organic solvent is selected from optionally substituted, preferably unsubstituted linear or cyclic aliphatic hydrocarbons, aromatic hydrocarbons or ether compounds, without being limited thereto.
  • ether compound shall mean any organic compound containing an ether group -0-, in particular of formula R 1 -O-R 2 , wherein Ri and R 2 , are independently selected from an organyl group R preferably having up to 20 carbon atoms and optionally one or more hetero atoms.
  • the organyl group R is selected from optionally substituted, preferably unsubstituted, alkyl, aryl, alkenyl, alkynyl, alkaryl, aralkyl, aralkenyl, aralkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, cycloaralkyl, cycloaralkenyl, cycloaralkynyl, alkoxy, aryloxy, and organosiloxy (cyclic and acyclic) groups, preferably alkyl, alkenyl and aryl groups.
  • Ri and R2 are substituted or unsubstituted linear or branched alkyl groups or aryl groups, which may have further heteroatoms such as oxygen, nitrogen, or sulfur.
  • Ri and R 2 can constitute together an optionally substituted alkylene or arylene group, which may have further heteroatoms such as oxygen, nitrogen, or sulfur.
  • the ether compounds can be symmetrical or asymmetrical with respect to the substituents at the ether group -0-.
  • ether compound also comprises linear ether compounds in which more than one ether group may be included, forming a di- , tri- , oligo- or polyether compound, wherein Ri and R 2 constitute organyl groups when they are terminal groups of the compounds, and alkylene or arylene groups when they are internal groups.
  • a terminal group is defined as any group being linked to one oxygen atom which is part of an ether group, while an internal group is defined as any group linked to two oxygen atoms being a constituent of ether groups.
  • Preferred examples of such compounds are dimethoxy ethane, glycol diethers (glymes) , in particular diglyme or tetraglyme, without being limited thereto.
  • high-boiling ether compound is defined as an ether compound according to above definition with a boiling point at about 1 bar (ambient pressure) of preferably at least about 70 °C, more preferably at least about 85 °C, even more preferably at least about 100 °C, and most preferably at least about 120 °C.
  • the application of high-boiling ethers in the present invention is favourable as it facilitates separation of the desired products of the general formula (I) from the reaction mixture containing the solvent and residual starting materials.
  • the products of the general formula (I) in general have lower boiling points than the starting materials, and the boiling points of these products are also lower than the boiling point of high-boiling ethers of above definition.
  • the boiling points of selected representative products of the general formula (I) are about 35 °C (Me 2 SiHCI) , about 41 °C (MeSiHC ) or about 57 °C (Me 3 SiCI), while representative higher-boiling ether compound diglyme has a boiling point of about 162 °C, and the boiling point of a mixture of methylchlorodisilanes principally consisting of isomers of trimethyltrichlorodisilane and dimethyltetrachlorodisilanes, which are respective substrates of the general formula (I I) is about 151 -158 °C.
  • step A) is carried out in the presence of at least one compound of the formula R 4 PCI.
  • R is independently a hydrogen group or an organyl group, more preferably a hydrogen group, an aromatic group or an aliphatic hydrocarbon group.
  • R is independently a hydrogen or an alkyl, cycloalkyl, aryl or alkaryl group of from 1 to 30 carbon atoms.
  • R preferably includes alkyl having up to 16 carbon atoms such as methyl, butyl such as n-butyl, iso-butyl, hexyl such as n-hexyl, tetradecyl, such as n-tetradecyl, octyl, such as n-octyl.
  • the amount of the at least one compound of the formula R 4 PCI is in the range of about 0.01 to about 99.95 wt-% , more preferred about 0.1 to about 75 wt-% , more preferred about 0.1 to about 55 wt-% , even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% based on the total weight of the silane substrate.
  • weight-% relates to the total weight of substrates of the general formulae (I I), (II I) and (IV) present in step A).
  • R 4 PCI Compounds of the formula R 4 PCI are suitable cleavage compounds, acting as catalysts for the disilane cleavage and as hydrogen source, as they are able to cleave partially or fully hydrogenated disilanes at room temperature, highly methylated disilanes at room temperature to about 140 °C without major decomposition reactions, wherein oligosilanes are formed as side-products. At higher temperatures, for instance about 180 to about 220 °C and/or longer reaction times is was found that they react with the silane substrates such as disilanes, oligosilanes and carbodisilanes under formation of H-silanes.
  • n- Bu 4 PCI when n- Bu 4 PCI is used, H-silanes are generated by decomposition of n-Bu 4 PCI to n-Bu 3 P and formally butyl chloride with subsequent formation of 1-butene and HCI.
  • step A) is carried out in the presence of at least one cleavage compound of the formula R 4 PCI and at least one methylimidazole.
  • each of the cleavage compounds is applied in an amount of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 75 wt-%, more preferred about 0.1 to about 55 wt-%, even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% is based on the total weight of the silane substrate.
  • At least one compound of the formula R 4 PCI and at least one methylimidazole are applied as cleavage reagent in step A).
  • the at least one methylimidazole is selected from the group of consisting of 1 -methylimidazole, 2-methylimidazole, 4-methylimidazole and 2,4-dimethylimidazole, most preferably it is 2-methylimidazole.
  • methylimidazole under certain conditions also act as a reactant in the cleavage reaction.
  • 2-methylimidazole reacted with Me 2 SiCI 2 to compound 1 (140-160°C) (see equation below).
  • This molecule reacts at higher temperatures (>200°C) to compound 2, which could be characterized b X-ray diffractio
  • the at least one compound of the formula R 4 PCI is selected from the group consisting of tetra(n-butyl)phosphonium chloride, methyltri(isobutyl)phosphonium chloride, tetra(n-octyl)phosphonium chloride, tri(n- butyl)tetradecylphosphonium chloride and octyltri(butyl)phosphonium chloride, most preferably it is tetra(n-butyl)phosphonium chloride (n-Bu 4 PCI) .
  • step A) is carried out in the presence of n-Bu 4 PCI.
  • n-Bu PCI is applied in an amount of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 75 wt-%, more preferred about 0.1 to about 55 wt-% , even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% is based on the total weight of the silane substrate.
  • step A) is carried out in the presence of n-Bu PCI and 2-methylimidazole.
  • each of the cleavage compounds is applied in an amount of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 75 wt-%, more preferred about 0.1 to about 55 wt-%, even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% is based on the total weight of the silane substrate.
  • step A) is carried out in the presence of at least one compound of the formula R 4 PCI and at least one metal hydride, preferably lithium hydride.
  • the amount of the at least one metal hydride is in the range of about 1 mol-% to about 600 mol-%, preferably about 1 to about 400 mol-%, more preferably about 1 to about 200 mol-%, most preferably about 25 to about 150 mol-% , based on the total molar amount of the chlorine atoms present in silane substrate compounds, while the amount of the at least one compound of the formula R 4 PCI is in the range from about 0.01 to about 99.95 weight-% , more preferably from about 0.1 to about 60 weight-%, even more preferably from about 1 to about 25 weight-%, and most preferably from about 1 to about 5 weight-% based on the total amount of the silane substrate.
  • the substrates of the general formulae (I I), (I I I) and (IV) are partially or completely hydrogenated before or during the cleavage reaction takes place.
  • the resulting partially or fully hydrogenated substrates of the general formulae (I I) , (I II) and (IV) are more readily cleavable by cleavage reagents of the formula RPCI 4 than their analogues prior to hydrogenation. Accordingly, lower reaction temperatures can be applied for cleavage, and the percentage of hydrogen substituents in the resulting silanes of the general formula (I) is increased by such reaction conditions.
  • the content of hydrogen substituents in the products of the general formula (I) is also increased by hydrogenation of cleavage products of the general formula (I) bearing chloro substituents, which is effected by the presence of a metal hydride in step A) .
  • step A) is carried out in the presence of n-Bu PCI and lithium hydride.
  • n-Bu PCI does not preclude the presence of further cleavage reagents in the reaction mixture of step A)
  • lithium hydride does not preclude the presence of further hydrogenation reagents in the reaction mixture of step A).
  • step A) is carried out in the presence of about 1 to about 200, preferably about 5 to about 100 mol-% n-Bu PCI in relation to the amount of the silane substrate compounds of the general formulae (I I), (I II) and (IV) and about 1 to about 600 mol-%, preferably about 1 to about 400 mol-% LiH in relation to the chlorine atoms present in the silane substrate compounds of the general formulae (I I) , (I I I) and (IV) .
  • the term "amount of silane substrate compounds” refers to the combined molar amounts of all disilanes of the general formula (I I) , oligosilanes of the general formula (I I I) or carbodisilanes of the general formula (IV) . In the determination of the molar amount these compounds are considered regardless if they are submitted as a part of a mixture comprising other silane compounds, in particular disilanes and carbodisilanes, which do not fall under the general formulae (I I), (I II) or (IV) .
  • the amount of lithium hydride is in the range of from about 1 to about 600 mol-% , more preferably from about 10 to about 350, even more preferably from about 25 to about 200, and most preferably from about 25 to about 100 mol-% based on the molar amount of the chlorine atoms present in the silane substrate compounds of the general formulae (I I) , (II I) and (IV) , while the amount of n-Bu 4 PCI is preferably in the range from about 0.01 to about 99.95 wt-% more preferably from about 0.1 to about 60 wt-%, even more preferably from about 1 to about 25 wt-%, and most preferably from about 1 to about 10 wt-% based on the total weight of the silane substrate.
  • step A) is conducted at a temperature of about 0 °C to about 300 °C, more preferably 20 °C to 280 °C. More preferably the temperature is at least about 100 °C, more preferably at least about 150 °C, more preferably at least 200 °C and most preferably at least 220 °C.
  • the reaction time is preferably at least about 4 hours, more preferably at least about 6 hours, more preferably at least about 8 hours and most preferably at least about 10 hours.
  • Reaction temperature and reaction time of the cleavage reaction are suitably selected for a certain silane substrate and cleavage compound such that at least one of the following parameters is met:
  • the reaction temperature in step A) is the temperature of the reaction mixture, i.e. the temperature measured inside the reaction vessel in which the reaction is conducted.
  • step A) is carried out using at least one quaternary Group 15 onium compound represented by the formula R 4 QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 220 °C, and even more preferably at about 80 to about 160 °C.
  • R 4 QX a quaternary Group 15 onium compound represented by the formula R 4 QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 220 °C
  • step A) is carried out using at least one compound selected from heterocyclic amines and heterocyclic ammonium halides as cleavage compound, at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 220 °C, even more preferably at about 100 to about 220 °C, and most preferably at about 140 °C to about 220 °C.
  • step A) is carried out using at least one quaternary Group 15 onium compound represented by the formula R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, and at least one compound selected from heterocyclic amines and heterocyclic ammonium halides as cleavage compound, at a temperature of about 0 °C to about 300 °C, more preferably about 50°C to about 220 °C, even more preferably at about 100 to about 200 °C, and most preferably at about 120 °C to about 180 °C.
  • R4QX a quaternary Group 15 onium compound represented by the formula R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group
  • the reaction temperature in step A) according to the invention is the temperature of the reaction mixture, i.e. the temperature measured inside the reaction vessel in which the reaction is conducted.
  • the reaction vessel can be an ampoule, a sealed tube, a flask or any kind of chemical reactor, without being limited thereto.
  • reaction step A) is carried out in a suitably sized reactor made of materials, such as glass or Hastelloy C, which are resistant to corrosion by chlorides.
  • a means of vigorous agitation is provided to disperse or dissolve the cleavage reagent or mixtures of cleavage reagent and metal hydride in the solvent.
  • step A) is conducted at a pressure of about 0.1 bar to about 30 bar, more preferably at about 1 bar to about 20 bar, most preferably at about 1 bar to about 10 bar.
  • the indicated pressure ranges refer to the pressure measured inside the reaction vessel used when conducting reaction step A).
  • the weight ratio of the silane substrates to the organic solvent is in the range of about 1 to about 100 wt-%, more preferably in the range of about 10 to about 80 wt-%, even more preferably about 20 to about 60 wt-%, most preferably about 30 to about 50 wt-% based on the weight of the organic solvent and silane substrate.
  • the weight ratio of the cleavage compound to the organic solvent is in the range of about 0.01 to about 100 wt-%, more preferably in the range of about 0.1 to about 50 wt-%, even more preferably about 0.5 to about 20 wt-%, most preferably about 1 to about 10 wt-% based on the weight of the organic solvent and cleavage compound.
  • Step A) can be done also solvent free.
  • the weight-percentages of the silane substrates to the organic solvent and of the cleavage compound to the organic solvent as indicated before amount to about 100 wt-%.
  • the monosilanes of the formula (I) are selected from the group consisting of Me 2 SiHCI, Me 2 SiH 2 , Me 3 SiCI, Me 2 SiCI 2 , Me 3 SiH, MeSihh, MeSiHC , MeSiH 2 CI, and MeSiC .
  • the methylmonosilanes of the formula (I) are selected from the group consisting of Me 2 SiHCI, MeSiHC , MeSiH 2 CI, Me 3 SiCI, Me 3 SiH, Me 2 SiH 2 , MeSiH 3 and Me 2 SiCI 2 .
  • the monosilanes of the formula (I) are selected from the group consisting of Me 2 SiHCI, Me 3 SiCI, and MeSiHCb.
  • dimethylchloromonosilane Me 2 SiHCI is formed by submitting a substrate selected from the group consisting of CIMe 2 Si-SiMe 2 CI, CIMe 2 Si-SiMeCI 2 , Me 3 Si-SiMe 2 CI, HMe 2 Si-SiMe 2 H, HMe 2 Si-SiMeH 2 , Me 3 Si-SiMe 2 H, CIMe 2 Si-SiMe 2 H, CIMe 2 Si-SiMeH 2 , HMe 2 Si-SiMeCI 2, CIMe 2 Si-CH 2 -SiMeCI 2 , CI 2 MeSi-CH 2 -SiMeCI 2 CIMe 2 Si-CH 2 -SiMe 2 CI, Me 3 Si-CH 2 -SiMe 2 CI, CIMe 2 Si-SiMe 2 -SiMe 2 CI, CIMe 2 Si-SiMe 2 Si, CIMe 2
  • each of the above-stated substrates may be submitted to the reaction conditions as single substrate, in a mixture with other compounds of the above-stated compounds, or in a mixture with other substrates of the general formulae (II), (III) or (IV).
  • trimethylchlorosilane Me 3 SiCI is formed by submitting a substrate selected from the group consisting of Me 3 Si-SiMe 2 CI, Me 3 Si-SiMeCI 2 , Me 3 Si-SiMe 2 H, Me 3 Si-CH 2 -SiMe 2 CI, CIMe 2 Si- CH 2 -SiMe 2 CI, CIMe 2 Si-CH 2 -SiMeCI 2 Me 3 Si-CH 2 -SiMe 3 or Me 3 Si-CH 2 -SiMeCI 2 to the cleavage reactions of step A).
  • methyldichloromonosilane MeSiHCb is formed by submitting a substrate selected from the group consisting of CbMeSi-SiMeCb, CI 2 MeSi-SiMe 2 CI, CI 2 MeSi-SiMe 3 , HCIMeSi-SiMeH 2 , HCIMeSi-SiMeCIH, HCIMeSi-SiMeCb, CI 2 MeSi-SiMeH 2 , CIHMeSi-SiMe 2 CI, CI 2 MeSi-SiMe 2 H, CIHMeSi-SiMe 2 H, CI 2
  • the step B) of separating the resulting monosilanes of the formula (I) is carried out by distillation, low temperature condensation, or a combination thereof.
  • distillation in the sense of the present invention relates to any process for separating components or substances from a liquid mixture by selective evaporation and condensation. Therein, distillation may result in practically complete separation of the constituents of a mixture, thus leading to the isolation of nearly pure compounds, or it may be a partial separation that increases the concentration of selected constituents of the mixture in the distillate when compared to the mixture submitted to distillation.
  • the distillation processes which may constitute separation step B) can be simple distillation, fractional distillation, vacuum distillation, short path distillation or any other kind of distillation known to the skilled person.
  • the step B) of separating the monosilanes of the formula (I) according to the invention can comprise one or more batch distillation steps, or can comprise a continuous distillation process.
  • the term "low temperature condensation” may comprise separation or enrichment of one or more compounds of the general formula (I) from the reaction mixture by volatilization from the reaction vessel and condensation as a liquid and/or solid in a refrigerated vessel from which it can be subsequently recovered by distillation, or by solution in an ether solvent.
  • the monosilanes can be absorbed in an ether solvent contained in a refrigerated vessel.
  • the hydrogenation of the silane substrates prior to step A) is carried out using n-Bu 3 SnH for partial hydrogenation, or LiAlhU for complete hydrogenation.
  • the silane substrates comprising the silane substrate compounds of the general formulae (II), (III), and (IV), and the mixtures thereof are residues of the Rochow-Muller Direct Process (DPR).
  • the primary commercial method to prepare alkylhalosilanes and arylhalosilanes is through the Rochow-Muller Direct Process (also called Direct Synthesis or Direct Reaction), in which copper-activated silicon is reacted with the corresponding organohalide, in particular methyl chloride, in a gas-solid or slurry-phase reactor. Gaseous products and unreacted organohalide, along with fine particulates, are continuously removed from the reactor. Hot effluent exiting from the reactor comprises a mixture of copper, metal halides, silicon, silicides, carbon, gaseous organohalide, organohalosilanes, organohalodisilanes, carbodisilanes and hydrocarbons.
  • Rochow-Muller Direct Process also called Direct Synthesis or Direct Reaction
  • Hot effluent exiting from the reactor comprises a mixture of copper, metal halides, silicon, silicides, carbon, gaseous organohalide, organohalosilanes, organohal
  • this mixture is first subjected to gas-solid separation in cyclones and filters. Then the gaseous mixture and ultrafine solids are condensed in a settler or slurry tank from which the organohalide, organohalosilanes, hydrocarbons and a portion of organohalodisilanes and carbodisilanes are evaporated and sent to fractional distillation to recover the organohalosilane monomers.
  • the solids accumulated in the settler along with the less volatile silicon-containing compounds are purged periodically and sent to waste disposal or to secondary treatment. Organohalodisilanes and carbodisilanes left in the post-distillation residues are also fed to hydrochlorination.
  • DPR Direct Process Residue
  • disilanes in particular, methylchlorodisilanes of the general formula (II), oligosilanes of the general formula (III) and carbodisilanes of the general formula (IV), which are constituents of the side-products of the Rochow-Muller Direct Process (DPR), can be transformed to monosilanes of the general formula (I) via cleavage reactions, optionally involving hydrogenation of the substrates of the formulae (II), (III), and (IV) or the products (I).
  • DPR Rochow-Muller Direct Process
  • the process is performed under inert conditions.
  • inert conditions means that the process is partially or completely carried out under the exclusion of surrounding air, in particular of moisture and oxygen.
  • closed reaction vessels, reduced pressure and/or inert gases, in particular nitrogen or argon, or combinations of such means may be used.
  • y 0 to 3, preferably 1 to 3, more preferably 1 or 2,
  • n 0 to 6, preferably 0 to 4,
  • each Si atom preferably bears at least one methyl group, and wherein each Si atom preferably bears at least one methyl group, and c) one or more carbodisilanes of the general formula (IV)
  • b, d are independently from each other 0 to 2
  • e, f are independently from each other 0 to 2
  • cleavage compound selected from the group consisting of:
  • each R is independently a hydrogen or an organyl group
  • Q is phosphorus, arsenic, antimony or bismuth
  • X is a halide selected from the group consisting of F, CI, Br and I ,
  • step B) optionally a step of separating the resulting monosilanes of the general formula (I). 2. Process according to embodiment 1 , wherein the reaction in step A) is carried out for more than about 4 hours and at a temperature of at least about 200 °C, or the reaction in step A) is carried out for more than about 10 hours preferably, at a temperature of more than about 100 °C.
  • silane substrate is consisting of one or more silane substrate compounds selected from the group consisting of the disilanes of the general formula (II), linear or branched oligosilanes of the general formula (II I) and the carbodisilanes of the general formula (IV).
  • the quaternary Group 15 onium compound is represented by the formula R 4 PCI, wherein R is independently a hydrogen group or an organyl group, more preferably a hydrogen group, an aromatic group or an aliphatic hydrocarbon group.
  • step A) is carried out by subjecting the silane substrate to the cleavage reaction of step A) in the presence of a hydrogen halide HX, wherein X is selected from the group consisting of F, CI, Br and I.
  • step A) is carried out in the presence of at least one metal hydride, preferably at least one metal hydride selected from the group of alkali metal hydrides and alkaline earth metal hydrides, more preferably at least one alkali metal hydride, and most preferably lithium hydride.
  • at least one metal hydride preferably at least one metal hydride selected from the group of alkali metal hydrides and alkaline earth metal hydrides, more preferably at least one alkali metal hydride, and most preferably lithium hydride.
  • silane substrate comprises at least one of the compounds selected from the group consisting of
  • Si 2 CI 6 C MeSi-SiMeCIH, HCIMeSi-SiMeCIH, CI 2 MeSi-SiMeH 2 , HCIMeSi-SiMeH 2 , CIMe 2 Si- SiMeCIH, CI 2 MeSi-SiMe 2 H, CIMe 2 Si-SiMeH 2 , HMe 2 Si-SiMeCIH, CIMe 2 Si-SiMe 2 CI, Me 3 Si- SiMe 2 CI, CIMe 2 Si-SiMe 2 H, Me 3 Si-SiMe 2 H, HMe 2 Si-SiMe 2 H, H 2 MeSi-SiMeH 2 , HMe 2 Si- SiMeH 2 , CI 2 MeSi-SiMeCI 2 , CIMe 2 Si-SiMeCI 2 , Me 3 Si-SiMeCI 2 , CI 2 MeSi-SiM
  • the molar ratio of the cleavage compound used in step A) to the silane substrate compounds of the general formulae (II), (III) and (IV) is in the range of about 0.0001 to about 100 mol-%, more preferred 0.001 to 50 mol-%, more preferred 0.001 to 25 mol-%, even more preferred 0.01 to 10 mol- %, and most preferably 0.01 to 0.5 mol-% based on the molar amount of the silane substrate compounds.
  • step A) in relation to the silane substrate compounds of the general formulae (II), (II I) and (IV) is in the range of about 1 mol-% to about 600 mol-% , preferably about 1 to about 400 mol-%, more preferably about 1 to about 200 mol-%, most preferably about 25 to about 150 mol-% , based on the total molar amount of the chlorine atoms present in silane substrate compounds.
  • step A) is submitted to a hydrogenation step before the cleavage reaction of the silicon-silicon bond(s) in the silane substrates of the general formulae (I I) and (I I I) and/or the silicon-carbon bond(s) of the carbodisilanes of the general formula (IV) is carried out, wherein chlorine atoms contained in the silane substrates are partially or completely exchanged by hydrogen atoms.
  • a hydride donor selected from the group of metal hydrides, preferably complex metal hydrides and organometallic hydride reagents such as LiAIH 4 , n-Bu 3 SnH, NaBH 4 , / ' -BU 2 AIH or sodium bis(2-methoxyethoxy) aluminumhydride.
  • step A) is carried out in the presence of an organic solvent, preferably an high-boiling ether compound, more preferably diglyme or tetraglyme, most preferably diglyme.
  • organic solvent preferably an high-boiling ether compound, more preferably diglyme or tetraglyme, most preferably diglyme.
  • step A) is carried out in the presence of at least one compound of the formula R 4 PCI.
  • step A) is carried out in the presence of at least one compound of the formula R 4 PCI and at least one methylimidazole.
  • step A) is carried out in the presence of n-Bu4PCI.
  • step A) is carried out in the presence of n-Bu4PCI and 2-methylimidazole.
  • step A) is carried out in the presence of at least one compound of the formula R 4 PCI and at least one metal hydride, preferably lithium hydride.
  • step A) is carried out in the presence of n-Bu 4 PCI and lithium hydride.
  • step A) is carried out in the presence of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 75 wt- %, more preferred about 0.1 to about 55 wt-%, even more preferred about 1 to about 25 wt- % and most preferably about 2 to about 10 wt-% n-Bu 4 PCI wherein the weight percentage wt-% is based on the total weight of the silane substrate and about 1 mol-% to about 600 mol-%, preferably about 1 to about 400 mol-%, more preferably about 1 to about 200 mol-%, most preferably about 25 to about 150 mol-% LiH based on the total molar amount of the chlorine atoms present in silane substrate compounds.
  • step A) is conducted at a temperature of about 0 °C to about 300 °C, preferably at about 20 °C to about
  • step A) is carried out using at least one cleavage compound selected from quaternary Group 15 onium compounds represented by the formula R 4 QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I , at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 220 °C, and even more preferably at about 80 to about 160 °C.
  • R 4 QX quaternary Group 15 onium compounds represented by the formula R 4 QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I , at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C
  • step A) is carried out using at least one cleavage compound selected from heterocyclic amines and heterocyclic ammonium halides, at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 250 °C, even more preferably at about 100 to about 220 °C, and most preferably at about 140 °C to about 220 °C.
  • step A) is carried out using at least one cleavage compound selected from quaternary Group 15 onium compounds represented by the formula R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, and at least one cleavage compound selected from heterocyclic amines and heterocyclic ammonium halides, at a temperature of about 0 °C to about 300 °C, more preferably about 50 °C to about 250 °C, even more preferably at about 100 to 220 °C, and most preferably at 150 °C to 220 °C.
  • R4QX a halide selected from the group consisting of F, CI, Br and I
  • step A) is carried out using at least one cleavage compound selected from quaternary Group 15 onium compounds represented by the formula R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, and at least one cleavage compound selected from heterocyclic amines and heterocyclic ammonium halides, at a temperature of about 0 °C to about 300 °C, more preferably about 50 °C to about 220 °C, even more preferably at about 100 to about 200 °C, and most preferably at about 120 °C to about 180
  • step A) is conducted at a pressure of about 0.1 bar to about 30 bar, more preferably at about 1 bar to about 20 bar, most preferably at about 1 bar to about 10 bar.
  • the weight ratio of the silane substrate to the organic solvent is in the range of about 1 to about 100 wt-%, more preferably in the range of about 10 to about 80 wt-%, even more preferably about 20 to 60 about wt-%, most preferably about 30 to about 50 wt-% based on the weight of the organic solvent and silane substrate.
  • the weight ratio of the cleavage compound to the organic solvent is in the range of about 0.01 to about 100 wt-%, more preferably in the range of about 0.1 to about 50 wt-%, even more preferably about 0.5 to about 20 wt-%, most preferably about 1 to about 10 wt-% based on the weight of the organic solvent and cleavage compound.
  • dimethylchloromonosilane Me 2 SiHCI is formed by submitting a silane substrate selected from the group consisting of CIMe 2 Si-SiMe 2 CI, CIMe 2 Si-SiMeCI 2 , Me 3 Si-SiMe 2 CI, HMe 2 Si-SiMe 2 H, HMe 2 Si-SiMeH 2 , Me 3 Si-SiMe 2 H, CIMe 2 Si-SiMe 2 H, CIMe 2 Si-SiMeH 2 , HMe 2 Si-SiMeCI 2 , CI 2 MeSi-CH 2 -SiMeCI 2 CIMe 2 Si-CH 2 -SiMeCI 2 , CIMe 2 Si-CH 2 -SiMe 2 CI, Me 3 Si-CH 2 -SiMe 2 CI, CIMe 2 Si-SiMe 2 -SiMe 2 CI,
  • the trimethylchlorosilane Me 3 SiCI is formed by submitting a silane substrate selected from the group consisting of Me 3 Si-SiMe 2 CI, Me 3 Si-SiMeCI 2 , Me 3 Si-SiMe 2 H, Me 3 Si-CH 2 -SiMe 2 CI, CIMe 2 Si-CH 2 -SiMe 2 CI, CIMe 2 Si-CH 2 -SiMeCI 2 , Me 3 Si-CH 2 -SiMe 3 , Me 3 Si-CH 2 -SiMeCI 2 and mixtures thereof to the cleavage reactions of step A).
  • a silane substrate selected from the group consisting of Me 3 Si-SiMe 2 CI, Me 3 Si-SiMeCI 2 , Me 3 Si-SiMe 2 H, Me 3 Si-CH 2 -SiMe 2 CI, CIMe 2 Si-CH 2 -SiMe 2 CI, CIMe 2 Si-CH 2 -
  • methyldichloromonosilane MeSiHCI 2 is formed by submitting a silane substrate selected from the group consisting of CI 2 MeSi-SiMeCI 2 , CI 2 MeSi-SiMe 2 CI, CI 2 MeSi-SiMe 3 , HCIMeSi- SiMeH 2 , HCIMeSi-SiMeCIH, HCIMeSi-SiMeC , CI 2 MeSi-SiMeH 2 , CIHMeSi-SiMe 2 CI, CI 2 MeSi-SiMe 2 H, CIHMeSi-SiMe 2 H, CI 2 MeSi-CH 2 -SiMeCI 2 , CIMe 2 Si-CH 2 -SiMeCI 2 , Me 3 Si- CH 2 -SiMeCI 2 , (CI 2 MeSi) 2 Si
  • silane substrates of the general formulae (II) and (III), and the carbodisilane substrates of the general formula (IV), or the mixtures thereof are residues of the Rochow-Muller Direct Process (DPR).
  • DPR Rochow-Muller Direct Process
  • compositions comprising at least one monosilane of the general formula (I) as defined above, as obtainable by the process according to any of the previous embodiments.
  • the first section (Examples 1-14) is directed at detailed investigations of the performance of the cleavage compounds n-Bu 4 PCI, 2-methylimidazole (2-MIA) and derivatives thereof.
  • model compounds such as CIMe2Si-SiMe 2 CI were applied to study the influence of reaction temperature and reaction times. It was demonstrated that both cleavage compounds act as catalysts at lower reaction temperatures, while they act as reaction partners at high temperatures (in particular at about more than 180 °C, in particular at about 220 °C) and thus generate H-silanes (Me 2 SiHCI, MeSiHCI 2 ...) in high yields.
  • n-Bu4PCI already cleaves disilane substrates at low temperatures, such as r.t. to about 140 °C and also forms oligosilanes. At higher temperatures (about 180 to about 220 °C) H-silanes are formed.
  • the second section (Examples 15-27) is directed at the hydrogenation of the disilanes/monosilanes and cleavage of hydrogenated disilanes with the cleavage compounds (n-Bu 4 PCI and 2-MIA).
  • the aim of the experiments of the second section is to obtain higher yields of the H-substituted monosilanes. In the first place, this can be achieved by Cl- H-exchange of the disilanes and subsequent cleavage.
  • n-Bu 4 PCI is a suitable catalyst, as it is capable of cleaving partially and fully hydrogenated disilanes to monosilanes to full extent already at room temperature. At this, only a minor amount (about 5mol%) of the catalyst is decomposed in the case of highly methylated and hydrogenated disilanes, as the higher the degree of methylation of the disilanes is, the higher temperatures are required for cleavage.
  • Substrate 1 as defined in Table 1 above (260 mg) and the catalyst mixture (n-Bu 4 PCI, 2-MIA; 7 w% each) were reacted in a sealed NMR tube at 160° C for 25 hours. In a second reaction the mixture was directly heated to 220 °C. The results are listed in Table 8.
  • Tri- and tetrasilanes as displayed in Table 9 were synthesized from disilane 1 (4.3 g) and 1 MIA (0.5 g) in a 100 ml flask at 165 °C for 3 h.
  • Disilane 1 (523 mg) was admixed with 5 w% of 2-MIA in a sealed NMR tube. Heating of the sample to 140 °C for 23 h showed no significant reaction, after 48 h monomer 8 starts to form, and a lower amount of trisilane 26 and tetrasilane 27 were formed as well in a ratio of 1 :0.8:0.2. After 68 h reaction time, 26mol% of monosilanes were formed (8, 25mol%; 7, 1 mol%), 28mol% of disilane 1 remained unreacted, trisilane 26 was formed in 30mol%, and the tetrasilane 27 in 16mol%.
  • Disilane 1 (492 mg) was reacted with n-Bu 4 PCI (5 w%) at different temperatures and reaction times in a sealed NMR tube. Products formed are listed in Table 12. As demonstrated by Examples 8 and 9, both catalysts react similar at high temperatures. 2-MIA produced oligosilanes faster compared to n-Bu 4 PCI that subsequently were cleaved, while the phosphonium chloride formed oligosilanes that nearly simultaneously were reacted to monosilanes.
  • Disilane 1 (426 mg) was reacted separately with 5 w% of each catalyst (n-Bu PCI; 2-MIA) in a sealed NMR tube at 220 °C for 21 h, resulting in formation of the product mixtures listed in Table 13. It was shown that under these reaction conditions, hydridosilane formation was favoured with 2-MIA.
  • Disilane 1 (302 mg) was reacted with a mixture of n-Bu 3 P (30 mg) and butyl chloride (14 mg) in a sealed NMR tube at 220 °C for 70 h. Reaction products identified were monosilanes 8 (Me 2 SiCI 2 35mol%), 5 (Me 2 SiHCI 30mol%), 7 (Me 3 SiCI 13mol%), 9 (Me 3 SiH 2mol%) and 6 (Me2SiH2 2mol%). Besides these products, carbodisilane 21 was formed in 18mol%; other carbodisilanes with higher degree of chlorination were detected in traces.
  • Example 1 1 The disilane mixture listed in Example 1 1 (470 mg) as well as the mixture of oligosilanes (566 mg, Table 15) were reacted with both catalysts (2-MIA and n-Bu 4 PCI, 5 w% each) in a sealed NMR tube at 220 °C for 17 h. Products obtained are listed in Table 16. It is demonstrated that product formation in both cases is comparable. Cleavage reactions were quantitatively, no di- or oligosilanes remained unreacted. Table 16
  • the oligosilanes produced a significantly higher amount of hydrido silanes (17, 53mol%; 6, 6mol% vs. 17, 21 mol%, no 6) while the amount of chlorosilane 8 was significantly higher for the disilane mixture. (31 mol% vs. 9mol%).
  • n-Bu 4 PCI was completely converted to give n-Bu 3 P.
  • Disilane 1 (CIMe2Si-SiMe2CI, admixed with 5mol% Me3Si-SiMe2CI 2) (4.04 g) was reacted in a 1/1 molar ratio with the tin hydride in diglyme and tetraphenylphosphoniumchlonde (Ph 4 PCI, 3 w%) as catalyst at r.t.. After work up, a mixture of the disilanes 1 (15mol%), 2 (4mol%), 3 (72mol%) and 4 (9mol%) was obtained.
  • Tetramethyldisilane (80 mg, 10) was reacted with n-Bu 4 PCI (54 w%) in a sealed NMR tube and completely cleaved at 180 °C (17 h) to give Me 2 SiH 2 (6, 87mol%) Me 3 SiH (9, 7mol%), Me 2 SiHCI (5, 4mol%) and Me 3 SiCI (7, 2mol%).
  • Disilanes of sample II were mostly cleaved at r.t. to monomers, only 1 remained unreacted. At 220 °C (23 h) this disilane too was completely converted to monosilanes.
  • Example 2 The mixture of mono- and disilanes (357 mg) of Example 2 (listed in Table 5) was reacted with n-Bu3P (16 mg) in a diglyme/HCI solution (1 1.6 M) (molar ratio disilane/HCI 1 :1) in a sealed NMR tube at 80°C for 16.5 h to give monomers in 97.1 mol% (listed in Table 38). Only highly methylated disilanes 1 and 2 were still present. No oligomeric structures could be detected NMR spectroscopically. For this reaction no other hydrogen source was required except HCI that presumably reacted as a silylene trapping agent preventing the silylene insertion into the Si-Si-bond giving oligomeric structures. The main products formed were MeSiC (39.7mol%), Me 2 SiCI 2 (28.1 mol%) and MeSiHC (27.6mol%). Table 38
  • any compound, material or substance which is expressly or implicitly disclosed in the specification and/or recited in a claim as belonging to a group of structurally, compositionally and/or functionally related compounds, materials or substances includes individual representatives of the group and all combinations thereof.

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Abstract

The invention relates to a process for the manufacture of monosilanes of formula (I): MexSiHyClz (I), comprising: the step of subjecting a silane substrate (methyldisilanes, methyloligosilanes, or carbodisilanes) to a cleavage reaction of the silicon-silicon bond(s) or the silicon- carbon bonds in silane substrates the reaction involving a cleavage compound selected from a quaternary Group 15 onium compound R4 QX, a heterocyclic amine, a heterocyclic ammonium halide, or a mixture of R3P and RX. The starting material disilanes to be cleaved has the formula (II): MemSi2HnClo (II) The starting material oligosilanes to be cleaved have the general formula (III): MepSiqHrCIs (II I), The starting material carbodisilanes to be cleaved have the general formula (IV): (MeaSiHbCle)-CH2-(MecSiHdClf) (IV)

Description

Disilane-, carbodisilane- and oligosilane cleavage with cleavage compounds acting as catalyst and hydrogenation source
TECHNICAL FIELD
The present invention relates to the technical field of the production of silane monomers, in particular to the production of mono-, di- and trimethylmonosilanes, starting from disilanes and oligosilanes by a cleavage reaction of the silicon-silicon bond, and from carbodisilanes by silicon-carbon bond cleavage, in each case in the presence of a cleavage compound and optionally a hydrogenation source.
BACKGROUND OF THE INVENTION
Methylchlorosilanes and methylhydridosilanes are highly useful starting materials in synthetic organosilicon chemistry, and therefore constitute an industrially valuable class of compounds. I n particular, methylsilanes bearing both chloro- and hydrido substituents constitute attractive starting materials in synthesis due to their bifunctional nature, which means they have functional groups of different reactivities. The chloride ligand is a better leaving group than the hydride group and allows, for instance, the controlled addition of further monomeric or oligomeric siloxane units with retention of the Si-H bond under mild conditions, thereby rendering said chlorohydridosilanes useful as blocking and coupling agents in the synthesis of defined oligo- and polysiloxanes.
Such compounds generally find a wide range of applications, for instance for the manufacture of adhesives, sealants, mouldings, composites and resins for example in the fields of electronics, automotive, construction and many more. The Si-H moieties present in chlorosilanes can be utilized for postsynthesis modifications and functionalisations, for instance for the introduction of organic residues to polyorganosiloxanes or for cross-linking by hydrosilylation reactions, which is desirable in various kinds of compositions containing polyorganosiloxanes. Synthesis of functionalized polysiloxanes starting with transformations via the Si-H bond(s) followed by hydrolysis or alcoholysis of the Si-CI bond(s) and optionally condensation for the formation of polysiloxanes is also viable.
Although there is a high demand for such bifunctional silanes having both Si-H and Si-CI bonds, there is no practical, economically reasonable and sustainable industrial process for the synthesis of such building blocks disclosed yet. The production of methylsilanes by Si-Si-bond cleavage of disilanes has been reported by Lewis and Neely in WO 2013/101618 A1 (US 8,697,901 B2) and WO2013101619A1 (US 8,637,695 B2) . In these publications, the hydrochlorinative cleavage of the disilanes of the Direct Process Residue requires the presence of heterocyclic amines or group 15 quarternary onium compounds serving as catalysts, not as reactants. The yields of hydridomonosilanes, in particular of Me2SiHCI, are comparatively low. The scope of starting materials in above-cited publications is restricted to perchlorinated methyl disilanes. US 5175329A describes a process wherein a mixture of polysilanes and an organotrihalosilane are reacted with hydrogen gas in the presence of a hydrogenolysis catalyst, and a redistribution catalyst, at a temperature of 100° C to 400° C. In one run tetrabutylphosphonium chloride is used as redistribution catalyst. There is no pointer in US 5175329A according to that the redistribution catalyst would participate in the reaction. It is also unlikely that under the conditions of US 5175329A (hydrogen gas/pressure) the redistribution catalyst acts as a hydrogen donor. Moreover, the yields in Me2SiHCI are very low.
In EP 0574912 B1 (B. Pachaly, A. Schinabeck; 1993) a process for the preparation of methylchlorosilanes from the high-boiling residue from the Direct Process by Si-Si-bond cleavage with hydrogen chloride and a catalyst which remains in the reaction mixture, usually a tertiary amine, is described.
PROBLEM TO BE SOLVED
The problem to be solved by the present invention is the provision of a process for the production of monosilanes, in particular methylchloro- and methylhydridomonosilanes, and most preferred hydridosilanes, such as of Me2SiHCI in particular, by submitting disilanes, oligosilanes and carbodisilanes to cleavage conditions under which the desired products are obtained by Si-Si-bond cleavage, or by Si-C-bond cleavage in case of carbodisilanes acting as substrates. Further, it is the object of present invention to provide a process with improved product yields, product purity, product selectivity of the conversion, convenience of the workup procedure, ease of handling of the reagents and cost efficiency of the process. The problem to be solved is in particular the provision of such an improved process in which high proportions of methylhydridomonosilanes and methylhydridochloromonosilanes with a high content of hydride substituents can be obtained. Further, the problem to be solved comprises the provision of a process by which monosilanes such as in particular Me2SiHCI, Me2SiH2, Me3SiCI, Me2SiCI2, Me3SiH, MeSiH3, MeSiHCI2, MeSiH2CI, and MeSiC can be obtained in high yield from silane substrates, in particular from the residue of the Muller-Rochow Direct Process, the so-called Direct Process Residue (DPR).
According to the present invention, this problem is solved as described in the following.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a process for the production of monosilanes starting from disilanes, carbodisilanes, oligosilanes or mixtures thereof by cleavage of silicon-silicon bonds or carbon-silicon bonds, respectively, and to monosilanes produced by such process.
Subject of the invention is a process for the manufacture of monosilanes of the general formula (I):
MexSiHyClz (I), wherein
x = 0 to 3,
y = 0 to 3, preferably 1 to 3, more preferably 1 or 2,
z = 0 to 4 and
x + y + z = 4,
and mixtures thereof, comprising:
A) the step of subjecting a silane substrate comprising one or more silanes selected from the group of a) one or more disilanes of the general formula (II)
MemSi2HnClo (II)
wherein
m = 0 to 6,
n = 0 to 6, preferably 0 to 4,
o = 0 to 6 and
m + n + o = 6, b) one or more linear or branched oligosilanes of the general formula (III) MepSiqHrCIs (III),
wherein
q = 3-7
p = q to (2q + 2)
r, s = 0 to (q + 2)
r + s = (2q + 2) - p
and wherein preferably each Si atom bears at least one methyl group, and c) one or more carbodisilanes of the general formula (IV)
(MeaSiHbCle)-CH2-(MecSiHdClf) (IV)
wherein
a, c are independently of each other 1 to 3,
b, d are independently from each other 0 to 2
e, f are independently from each other 0 to 2,
a + b + e = 3,
c + d + f = 3,
and mixtures containing compounds of the general formulae (II), (II I) and (IV), to the cleavage reaction of the silicon-silicon bond(s) in the silane substrates of the general formulae (II) and (II I) and the silicon-carbon bond(s) of the carbodisilanes of the general formula (IV),
to the reaction with at least one compound (cleavage compound) selected from the group consisting of:
- a quaternary Group 15 onium compound R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I,
- a heterocyclic amine,
- a heterocyclic ammonium halide,
- a mixture of R3P and RX, wherein R is as defined above, and X is as defined above, and
mixtures of the above-mentioned compounds,
(i) until at least about 50 mol-% of the cleavage compound based on the initial molar amount of the cleavage compound is reacted, and/or (ii) until the ratio of the total of the produced monosilanes of the general formula (I) wherein y = 1 to 3 is at least about 40 mol-%, preferably at least about 50 mol-%, based on the total molar amount of the monosilanes of the general formula (I), and/or
(iii) until the ratio of Me2SiHCI is at least about 20 mol-%, preferably at least about 30 mol-%, based on the total amount of the monosilanes of the general formula (I), and
B) optionally a step of separating the resulting monosilanes of the general formula (I).
The cleavage reaction of the silicon-silicon bond(s) and/or the silicon-carbon bond(s) in the silane substrate is preferably carried out in the presence of at least one compound which promotes such bond cleavage and acts as a hydride donor (cleavage compound).
The disilanes of the general formula (II) MemSi2HnClo (II) can be depicted also by the structural formula:
R' R'
\ /
R' Si— Si— R'
/ \
R' R' wherein the substituents R' are independently selected from methyl (Me), hydrogen (H) and chlorine (CI), wherein the number of methyl groups m = 0 to 6, the number of hydrogen atoms n = 0 to 6, and the number of chlorine atoms o = 0 to 6, and the total of m + n + o = 6.
The carbodisilanes of the general formula (IV)
(MeaSiHbCle)-CH2-(MecSiHdClf) (IV) can be depicted also by the structural formula:
Figure imgf000007_0001
wherein the substituents R" are independently selected from methyl (Me), hydrogen (H) and chlorine (CI), and wherein the substituents R'" are independently selected from methyl (Me), hydrogen (H) and chlorine (CI), and wherein the number of methyl groups on each silicon atom (a, c) is independently from 1 to
3, wherein the number of hydrogen atoms on each silicon atom (b, d) is independently from 0 to 2, and wherein the number of chlorine atoms on each silicon atom (e, f) is independently from 0 to 2.
The linear or branched oligosilanes of the general formula (III)
MepSiqHrCIs (HI),
are oligosilanes that have a linear or branched silicon skeleton, wherein q = 3 to 7 silicon atoms are bonded to each other by single bonds, and the free valencies of the silicon skeleton are saturated by substituents selected from methyl (Me), hydrogen (H) and chlorine (CI) with the proviso that the number of methyl groups p = q to (2q + 2), which corresponds to the case where each silicon atom has one methyl group (p=q) and the case of permethylated silanes (p= 2q+2) and which means that there are at least 3 methyl groups up to 16 methyl groups (i.e. in Si7Mei6) in the silanes; and the number of hydrogen atoms (r) and chlorine atoms (s) are independently of each other 0 to (q + 2), and r + s = (2q + 2) - p, wherein q is the number of silicon atoms and p is the number of methyl groups, again with the preferred proviso that each Si atom bears at least one methyl group.
In a preferred embodiment of the invention the silane substrate is consisting of one or more silane substrate compounds selected from the group consisting of the disilanes of the general formula (II), linear or branched oligosilanes of the general formula (III) and the carbodisilanes of the general formula (IV).
The process of the present invention is characterized inter alia by any of the features (i) to (iii): (i) The process is run until at least about 50 mol-% of the cleavage compound based on the initial molar amount of the cleavage compound is reacted, and/or
(ii) The process is run until the ratio of the total of the produced monosilanes of the general formula (I) wherein y = 1 to 3 is at least about 40 mol-% , preferably at least about 50 mol-%, based on the total molar amount of the monosilanes of the general formula (I) .
(iii) The process is run until the ratio of Me2SiHCI is at least about 20 mol-%, preferably at least about 30 mol-%, based on the total amount of the monosilanes of the general formula (I). Such features (i) to (iii) are based on the discovery that the cleavage compound under certain conditions also react with the silane substrate and acts as a hydrogen donor in such reaction. In the process of the present invention such features (i) to (iii) can be easily adjusted by setting in particular a suitable reaction time and/or a suitable reaction temperature, and by monitoring the progress of the reaction for example by GC-MS or NMR spectroscopy.
It has been found in particular by the inventors that the cleavage compounds under certain conditions do act as reactants, i.e. they are consumed in the cleavage reactions, and that by virtue of this the amount of the desirable hydridomonosilanes, such as Me2SiHCI in particular, is significantly increased. Reaction temperature and time are adjusted for a given silane substrate and a given cleavage compound so as to satisfy one or more of the conditions (i) to (iii) above, preferably condition (ii) and/or (iii) .
In a preferred embodiment of the process of invention (i) the process is run until at least about 50 mol-% of the cleavage compound based on the initial molar amount of the cleavage compound is reacted.
In a preferred embodiment of the process of invention (ii) the process is run until the ratio of the total of the produced monosilanes of the general formula (I) wherein y = 1 to 3 is at least about 40 mol-%, preferably at least about 50 mol-%, based on the total molar amount of the monosilanes of the general formula (I).
In a preferred embodiment of the process of invention (iii) the process is run until the ratio of Me2SiHCI is at least about 20 mol-%, preferably at least about 30 mol-%, based on the total amount of the monosilanes of the general formula (I). In the process of the present invention it is possible that one of the features (i) to (iii) is adjusted, or that two of the features (i) to (iii) are adjusted or that preferably all of the features (i) to (iii) are adjusted. In a preferred embodiment of the process according to the invention, the reaction in step A) is carried out for more than about 4 hours, preferably more than about 6 hours, and at a temperature of at least about 200 °C, or the reaction in step A) is carried out for more than about 10 hours preferably more than about 12 hours, at a temperature of more than about 100 °C, preferably more than about 150°C.
Since the cleavage compound acts as a hydrogen donor, there is no need for any hydrogen gas (H2) supply to the process different to some of the prior art processes. Accordingly, the process of the present invention is normally carried out without the supply of hydrogen (H2). This advantageously also avoids the use of high pressure equipment since the process of the present invention can be usually carried out at normal pressure.
In the process of the present invention, one compound of general formula (I) or a mixture of more than one compound of general formula (I) is formed. More preferably, mixtures of more than one compound of the formula (I) are formed.
Further preferably, the monosilanes of the general formula (I) formed in the process of the present invention include compounds selected from the group of: MeSiH2CI, Me2SiH2, Me2SiHCI, Me3SiH, Me3SiCI, MeSiHC , Me2SiCI2, MeSiC and MeSihh. The one or more disilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula (II), wherein m = 0 to 6,
and preferably m = 2 to 6.
More preferably, the disilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula (II) with m = 2 to 6, wherein n = 0. Such disilanes are in particular constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the methyldisilanes Me3Si-SiMe2CI, CIMe2Si-SiMe2CI, CI2MeSi-SiMeCI2, CIMe2Si-SiMeCI2, Me3Si-SiMeCI2, which are therefore preferred substrates in the process according to the invention. Also preferably, the disilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula (II) with m = 2 to 4, wherein n > 0 and o > 0. Such disilanes are partially hydrogenated derivatives in particular of constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the methyldisilanes HMe2Si-SiMe2CI, H2MeSi-SiMeCIH, HCIMeSi-SiMeCIH, CIHMeSi-SiMeC , H2MeSi-SiMeCI2, HMe2Si-SiMeCI2, CIMe2Si-SiMeH2, HMe2Si-SiMeCIH, CIMe2Si-SiMeCIH and Me3Si-SiMeCIH.
Also preferably, the disilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula (II) with m = 2 to 5, wherein n = 1 to 3 and o = 0. Such disilanes are fully hydrogenated derivatives of in particular constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the methyldisilanes, HMe2Si-SiMe2H, H2MeSi-SiMeH2, HMe2Si-SiMeH2, Me3Si-SiMeH2 and Me3Si-SiMe2H.
The one or more linear or branched oligosilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula formula (I II), wherein
q = 3-7
p = q to (2q + 2)
r, s = 0 to (q + 2)
r + s = (2q + 2) - p
and wherein each Si atom bears at least one methyl group,
and preferably p = q to 2q. More preferably, the oligosilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula (III) with p = q to 2q, wherein r = 0. Such oligosilanes are constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, and include for example the methyloligosilanes CIMe2Si-SiMe2-SiMe2CI, CIMe2Si-SiMe2-SiMe2-SiMe2CI, (CIMe2Si)3SiMe, (CI2MeSi)2SiMeCI, (CI2MeSi)3SiMe, (CI2MeSi)2SiMe-SiCIMe-SiCI2Me, [(CI2MeSi)2SiMe]2, [(CI2MeSi)2SiMe]2SiCIMe,
(CI2MeSi)2SiMe-SiMe2CI, and are therefore preferred substrates in the process according to the invention.
Also preferably, the oligosilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula (III) with p = q to 2q, wherein r > 0 and s > 0. Such oligosilanes are partially hydrogenated derivatives in particular of constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the methyloligosilane CIMe2Si-SiMe2SiMe2H.
Also preferably, the oligosilanes subjected to the cleavage reaction of the silicon-silicon bond are represented by the general formula (III) with p = q to 2q, wherein s = 0. Such oligosilanes are fully hydrogenated derivatives of constituents in particular of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the methyloligosilanes HMe2Si- SiMe2-SiMe2H, HMe2Si-SiMe2-SiMe2-SiMe2H, (HMe2Si)3SiMe, (H2MeSi)2SiMeH, (H2MeSi)3SiMe, (H2MeSi)2SiMe-SiHMe-SiH2Me, [(H2MeSi)2SiMe]2, [(H2MeSi)2SiMe]2SiHMe, (H2MeSi)2SiMe-SiMe2H.
The one or more carbodisilanes subjected to the cleavage reaction of the silicon-carbon bonds linking the silyl groups with the methylene group are represented by the general formula (IV), wherein
a, c are independently of each other 1 to 3,
b, d are independently from each other 0 to 2
e, f are independently from each other 0 to 2,
a + b + e = 3,
c + d + f = 3,
and preferably a + c = 2 to 5.
More preferably, the carbodisilanes subjected to the cleavage reaction of the silicon-carbon bonds are represented by the general formula (IV) with a + c = 2 to 5, wherein b = d = 0. Such carbodisilanes are constituents of in particular the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the carbodisilanes CI2MeSi-CH2-SiMeCI2, CIMe2Si-CH2-SiMeCI2, CIMe2Si-CH2-SiMe2CI, Me3Si-CH2-SiMeCI2 and Me3Si-CH2-SiMe2CI, and are therefore preferred substrates in the process according to the invention.
Also preferably, the carbodisilanes subjected to the cleavage reaction of the silicon-carbon bonds are represented by the general formula (IV) with a + c = 2 to 4, wherein b + d > 0 and e + f > 0. Such carbodisilanes are partially hydrogenated derivatives of constituents of in particular the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the carbodisilanes HCIMeSi-CH2-SiMeCIH, HMe2Si-CH2-SiMeCI2, HMe2Si-CH2- SiMe2CI, and Me3Si-CH2-SiMeCIH. Also preferably, the carbodisilanes subjected to the cleavage reaction of the silicon-carbon bonds are represented by the general formula (IV) with a + c = 2 to 5, wherein e + f = 0. Such carbodisilanes are fully hydrogenated derivatives of constituents of the Direct Process Residue (DPR) from the Rochow-Muller Direct Synthesis, for example the carbodisilanes H2MeSi-CH2-SiMeH2, HMe2Si-CH2-SiMeH2, HMe2Si-CH2-SiMe2H, Me3Si-CH2-SiMeH2, Me3Si-CH2-SiMe2H.
The substrates according to the general formulae (I I) , (I I I) and (IV) may be submitted to the conditions for cleavage reactions in step A) as single compounds represented by general formulae (I I), (II I) and (IV), as a mixture of compounds represented by general formulae (I I), (II I) and (IV) exclusively, or as mixtures comprising one or more compounds represented by general formulae (I I), (I I I), or (IV).
Therein, cleavage is the term used to describe the transformation by which disilanes represented by the general formula (I I) , oligosilanes represented by the general formula (I I I) and carbodisilanes represented by the general formula (IV) are reacted to produce monomeric silanes represented by the general formula (I). In the case of disilanes of the general formula (I I) and oligosilanes of the general formula (I I I), the term "cleavage reaction of the silicon-silicon bond(s)" further indicates that according to the invention, the cleavage of the aforementioned substrates is effected by breaking the bond connecting the silicon atoms of these disilanes and oligosilanes. I n the case of carbodisilanes of the general formula (I I I) , the term "cleavage reaction of the silicon-carbon bonds" indicates that the cleavage reaction is effected by breaking one or both bonds between the silyl groups of the compounds and the methylene group linking the silyl groups. Such cleavage processes comprise in particular hydrochlorination and hydrogenolysis reactions. The optional step of separating the resulting monosilanes of the general formula (I) refers to any technical means applied to raise the content of one or more monosilanes according to the general formula (I) in a product mixture, or which results in the separation of single compounds of the formula (I) from a product mixture obtained in step A) of the process according to the invention.
In a preferred embodiment of the process according to the invention, step A) is carried out by subjecting the silane substrate to the cleavage reaction of the silicon-silicon bond(s) or the silicon-carbon bond(s) in the silane substrate in the presence of at least one compound (cleavage compound) selected from the group consisting of
- quaternary Group 15 onium compounds R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F (fluorine), CI (chlorine), Br (bromine) and I (iodine),
- heterocyclic amines and heterocyclic ammonium halides,
and mixtures of the above-mentioned compounds.
Preferably mixtures of a) heterocyclic amines and/or heterocyclic ammonium halides and b) quaternary Group 15 onium compounds R4QX are used.
In one embodiment, the cleavage compound comprises about 0.01 weight percent to about 99.95 weight percent of a) heterocyclic amines and/or heterocyclic ammonium halides and from about 0.05 weight percent to about 99.9 weight percent of b) quaternary Group 15 onium compounds based on the total weight of components a) and b). In a preferred embodiment, the cleavage compound contains about 5 wt% to about 85 wt% of 2- methylimidazole and about 95 wt% to about 15 wt% of tetra(n-butyl)-phosphonium chloride based on the total weight of the 2-methylimidazole and the tetra(n-butyl)-phosphonium chloride. Advantageously, the weight ratio of a) the heterocyclic amines and/or the heterocyclic ammonium halides relative to b) the-quaternary Group 15 onium compounds is from about 1 :9 to about 9: 1 , more advantageously from about 1 :3 to about 3: 1 . On a molar basis, in certain embodiments, it is desirable to have a molar excess of heterocyclic amines and/or heterocyclic ammonium halides relative to quaternary Group 15 onium compounds. Thus, in the case of tetra(n-butyl)phosphonium chloride and 2-methyimidazole, the molar ratio of the imidazole to the phosphonium chloride can be from about 1 .1 to about 100, specifically about 1 .5 to about 60 and more specifically about 1.5 to about 20. In the sense of the present invention, an organyl group is any organic substituent group, regardless of functional type, having one free valence at a carbon atom.
Preferably, the quaternary Group 15 onium compound R4QX is represented by the formula R4PCI wherein R is independently a hydrogen group or an organyl group, more preferably a hydrogen group, an aromatic group preferably having up to about 30 carbon atoms or an aliphatic hydrocarbon group preferably having up to about 30 carbon atoms.
Even more preferably, R is independently a hydrogen or an alkyl, cycloalkyl, aryl or alkaryl group having from about 1 to about 30 carbon atoms, preferably about 2 to about 16 carbon atoms. Preferred groups R include methyl, butyl such as n-butyl, iso-butyl, hexyl such as n- hexyl, tetradecyl, such as n-tetradecyl, octyl, such as n-octyl.
Particularly preferred examples of the quaternary 15 onium compound according to the invention are tetra(n-butyl)phosphonium chloride, tetra(n-butyl)phosphonium bromide, trihexyl(tetradecyl)phosphonium bromide, methyltri(isobutyl)phosphonium bromide, methyltri(isobutyl)phosphonium chloride, tetra(n-octyl)phosphonium chloride, tri(n- butyl)tetradecylphosphonium chloride, and octyltri(n-butyl)phosphonium chloride.
Preferably, the heterocyclic amine according to the invention has at least one nitrogen atom in at least one 4- to 8-membered hydrocarbon ring, wherein the ring atoms adjacent to the nitrogen are carbon or nitrogen, and the hydrocarbon ring or rings are, independently of one another, aromatic or non-aromatic hydrocarbon rings.
More preferably, the heterocyclic amine contains a five-membered ring with 1 to 3 nitrogen atoms.
Even more preferably, the heterocyclic amine is imidazole or a substituted imidazole selected from the group consisting of 1 -methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2- isopropyl-imidazole, 4-methylimidazole, 2,4-dimethylimidazole, 2-(2-imidazolyl)imidazole, 2- phenylimidazole, imidazoline, imidazolidine, pyrazole, 3-methylpyrazole, pyrrolidone, N- methylpyrrolidone, 1 ,3-dimethyl-2-imidazolidone, 1 ,2,3-triazole, and 1 ,2,4-triazole.
Preferably, the heterocyclic ammonium halide is derived from a heterocyclic amine having at least one nitrogen atom in at least one 4- to 8-membered hydrocarbon ring, wherein the ring atoms adjacent to the nitrogen are independently carbon or nitrogen atoms, and the hydrocarbon ring or rings are, independently of one another, aromatic or non-aromatic hydrocarbon rings, wherein the halide is fluoride, chloride, bromide.
More preferably, the heterocyclic ammonium halide is derived from a heterocyclic amine with 1 to 3 nitrogen atoms in a five-membered ring , and the halide is fluoride, chloride, bromide or iodide.
Even more preferably, the heterocyclic ammonium halide is 1 ,2-dimethyl-3-(n-propyl)- imidazolium chloride, 1 -ethyl-3-methylimidazolium bromide, 1 ,2-dimethyl-3-(n- butyl)imidazolium chloride, 1 -butyl-3-methyl-imidazolium chloride, 1 -(3-cyanopropyl)-3- methylimidazolium chloride, or 1 -methylimidazolium chloride.
In another preferred embodiment according to the invention, the quaternary Group 15 onium compound is represented by the formula R4PCI, wherein R is independently a hydrogen group or an organyl group, more preferably a hydrogen group, an aliphatic hydrocarbon or an aromatic group.
Preferably, R is independently a hydrogen or an alkyl, cycloalkyi, aryl or alkaryl group of about 1 to about 30 carbon atoms, preferably about 2 to about 16 carbon atoms. R include methyl, butyl such as n-butyl, iso-butyl, hexyl such as n-hexyl, tetradecyl, such as n- tetradecyl, octyl, such as n-octyl as substituents. Particularly preferred examples of the quaternary 15 onium compound according to the invention are tetra(n-butyl)phosphonium chloride, tetra(n-butyl)phosphonium bromide, trihexyl(tetradecyl)phosphonium bromide, methyltri(isobutyl)phosphonium bromide, methyltri(isobutyl)phosphonium chloride, tetra(n-octyl)phosphonium chloride, tri(n- butyl)tetradecylphosphonium chloride, and octyltri(butyl)phosphonium chloride.
In a further preferred embodiment of the process according to the invention, the compounds of the formula R4PCI are formed in situ from compounds of the formulae R3P and RCI, wherein R is preferably an organyl group as defined above.
Herein, R represents independently a hydrogen or any organyl group as defined above. More preferably, R is independently a hydrogen or an alkyl, cycloalkyl, aryl or alkaryl group from about 1 to about 30 carbon atoms, preferably about 2 to about 16 carbon atoms. This embodiment comprises in particular also that step A) of the process according to the invention which is carried out with a mixture of a phosphine R3P, wherein R is as defined above, such as n-Bu3P, and HX, preferably HCI, preferably in an ether solvent.
In another preferred embodiment of the process according to the invention, step A) is carried out by subjecting the silane substrates of the general formulae (I I) , (I I I) or (IV) or mixtures thereof to the cleavage reactions of step A) in the presence of a hydrogen halide HX, wherein X is selected from the group consisting of F, CI, Br and I .
Preferably, the hydrogen halide is HCI.
In a preferred embodiment of the process according to the invention, step A) is carried out in the presence of at least one metal hydride, preferably at least one metal hydride selected from the group of alkali metal hydrides and alkaline earth metal hydrides, more preferably at least one alkali metal hydride, and most preferably lithium hydride.
By the presence of at least one metal hydride in step A), a hydrogenation reaction of the substrates of the general formulae (I I) , (I I I) and (IV) or of the products of the general formula (I) also takes place before, during or after the cleavage reaction of the substrates of the general formulae (I I), (I I I) and (IV) under the reaction conditions of step A) . In the sense of the present invention, the term "hydrogenation" refers to the exchange of at least one chloro substituent of a compound by a hydrogen substituent by means of a hydride reagent. Preferably, one or more chloro substituents of at least one or more compounds of the general formulae (II), (III) or (IV) submitted to the reaction conditions of step A) are replaced by hydrogen substituents before or during the cleavage reaction by the presence of a metal hydride in reaction step A). Also preferably, one or more chloro substituents of at least one or more monosilanes of the general formula (I) obtained in step A) or being part of the substrate mixture are replaced by hydrogen substituents before, during or after the cleavage reaction by the presence of a metal hydride in step A). By such hydrogenation reactions, the ratio of hydrogen substituents to chloro substituents in the products of the general formula (I) is increased.
In a further preferred embodiment of the process according to the invention, the silane substrate comprises at least one of the compounds selected from the group consisting of Si2CI6, C MeSi-SiMeCIH, HCIMeSi-SiMeCIH, CI2MeSi-SiMeH2, HCIMeSi-SiMeH2, CIMe2Si- SiMeCIH, CI2MeSi-SiMe2H, CIMe2Si-SiMeH2, HMe2Si-SiMeCIH, CIMe2Si-SiMe2CI, Me3Si- SiMe2CI, CIMe2Si-SiMe2H, Me3Si-SiMe2H, HMe2Si-SiMe2H, H2MeSi-SiMeH2, HMe2Si- SiMeH2, CI2MeSi-SiMeCI2, CIMe2Si-SiMeCI2, Me3Si-SiMeCI2, CI2MeSi-CH2-SiMeCI2, CIMe2Si- CH2-SiMeCI2, CIMe2Si-CH2-SiMe2CI, Me3Si-CH2-SiMeCI2, Me3Si-CH2-SiMe2CI, Me3Si-CH2- SiMe3, CIMe2Si-SiMe2-SiMe2CI, CIMe2Si-SiMe2-SiMe2-SiMe2CI, (CIMe2Si)3SiMe, CIMe2Si- SiMe2SiMe2H, (CI2MeSi)2SiMeCI, (CI2MeSi)3SiMe, (CI2MeSi)2SiMe-SiCIMe-SiCI2Me, [(CI2MeSi)2SiMe]2, [(CI2MeSi)2SiMe]2SiCIMe, and (CI2MeSi)2SiMe-SiMe2CI.
In another preferred embodiment of the process according to the invention, the molar ratio of the cleavage compound used in step A) to the silane substrate compounds of the general formulae (II), (III) and (IV) is in the range of about 0.0001 to about 100 mol-%, more preferred 0.001 to 50 mol-%, more preferred 0.001 to 25 mol-%, even more preferred 0.01 to 10 mol- %, and most preferably 0.01 to 0.5 mol-% based on the molar amount of the silane substrate compounds. Herein, the molar ratio is defined as n (cleavage reagent in step A)) / n (substrates of the general formulae (II), (III) and (IV) in step A). In another preferred embodiment of the process according to the invention the weight ratio of the cleavage compound used in step A) to the silane substrate compounds of the general formulae (II), (III) and (IV) is in the range of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 75 wt-%, more preferred about 0.1 to about 55 wt-%, even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% based on the total weight of the silane substrate.
For the determination of this ratio, all compounds being methyldisilanes of the general formula (II), oligosilanes of the general formula (I II) and carbodisilanes of the general formula (IV) submitted to the reaction step (A) are considered, regardless if they are submitted as a part of a mixture comprising other compounds, in particular disilanes and carbodisilanes, which do not fall under the general formulae (II), (III) or (IV).
Process according to any of the previous embodiments, wherein the amount of the metal hydride in step A) in relation to the silane substrate is in the range of about 1 mol-% to about 600 mol-%, preferably about 1 to about 400 mol-%, more preferably about 1 to about 200 mol-%, most preferably about 25 to about 150 mol-%, based on the total molar amount of the chlorine atoms present in silane substrate compounds. In a preferred embodiment of the process according to the invention the molar ratio of the metal hydride in step A) to the chlorine atoms present in the methyldisilanes of the general formula (II), the oligosilanes (III), or the carbodisilanes of the general formula (IV), or mixtures thereof is in the range of about 1 to about 300 mol-%, more preferred about 10 to about 150 mol-%, even more preferred about 25 to about 100 mol-%, and most preferred about 25 to about 75 mol-% based on the total molar amount of the chlorine atoms present in silane substrate compounds.
In a preferred embodiment of the process according to the invention, the amount of the metal hydride in step A) in relation to the silane substrate is in the range of about 1 mol-% to about 400 mol-%, preferably about 1 to about 200 mol-%, more preferably about 1 to about 100 mol-%, most preferably about 25 to about 50 mol-%, based on the total molar amount of the silane substrate compounds. Herein, the molar ratio is defined as n (metal hydride in step A)) / n (silane substrates of the general formulae (II), (II I) and (IV) in step A). For the determination of this ratio, all compounds being methyldisilanes of the general formula (II), oligosilanes of the general formula (I II) and carbodisilanes of the general formula (IV) submitted to the reaction step (A) are considered, regardless if they are submitted as a part of a mixture comprising other compounds, in particular disilanes and carbodisilanes, which do not fall under the general formulae (II), (III) or (IV). In an additional preferred embodiment of the process according to the invention, the silane substrates used in step A) are submitted to a hydrogenation step before the cleavage reaction of the silicon-silicon bond(s) is carried out, wherein chlorine atoms contained in the silane substrates are partially or completely exchanged by hydrogen atoms. In the sense of the present invention, the term "hydrogenation" refers to the exchange of at least one chloro substituent of a compound by a hydrogen substituent by means of a hydride reagent.
Preferably, one or more chloro substituents of at least one or more compounds of the general formulae (II), (I II) or (IV) which are later submitted to the reaction conditions of step A) are replaced by hydrogen substituents before these silane substrates are submitted to reaction step A).
Also preferably, the hydride reagent used in the hydrogenation step is selected from the group of metal hydrides and organometallic hydride reagents, such as diisobutyl aluminium hydride (DIBAL-H), tributyltin hydride (n-Bu3SnH) or sodium bis(2-methoxyethoxy) aluminumhydride.
The term "metal hydrides" in the sense of the present invention comprises complex metal hydrides, such as LiAIH4 and NaBH4.
More preferably, the hydride reagent used for the partial or complete reduction of substrate compounds of the general formulae (I I), (III) or (IV) is tributyltin hydride (n-Bu3SnH), even more preferably tributyltin hydride (n-Bu3SnH) in combination with tetraphenylphosphonium chloride (Ph4PCI) as catalyst, and most preferably tributyltin with Ph4PCI as catalyst in diglyme as solvent.
By submitting the substrates of the general formulae (II), (III) or (IV) to such hydrogenation reactions before step A) is conducted, the ratio of hydrogen substituents to chloro substituents in the products of the general formula (I) is increased. In a further preferred embodiment of the process according to the invention, the hydrogenation of the silane substrates prior to step A) is carried out with a hydride donor selected from the group of metal hydrides, preferably complex metal hydrides and organometallic hydride reagents such as LiAIH4, n-Bu3SnH, NaBH4, /'-BU2AIH or sodium bis(2-methoxyethoxy)aluminumhydride.
According to the invention, the term hydride donor refers to any compound which is capable of donating at least one hydride anion used in a hydrogenation reaction of substrates of the general formulae (I), (II), (III) or (IV) which bear at least one chloro substituent.
In the sense of present invention, the term metal hydride refers to any hydride donor containing at least one metal atom or metal ion.
The term "complex metal hydrides" according to the invention refers to metal salts wherein the anions contain hydrides. Typically, complex metal hydrides contain more than one type of metal or metalloid. As there is neither a standard definition of a metalloid nor complete agreement on the elements appropriately classified as such, in the sense of present invention the term "metalloid" comprises the elements boron, silicon, germanium, arsenic, antimony, tellurium, carbon, aluminum, selenium, polonium, and astatine.
The term "organometallic hydride reagent" refers to compounds that contain bonds between carbon and metal atoms, and which are capable of donating at least one hydride anion used in a hydrogenation reaction of substrates of the general formulae (I), (II), (III) or (IV) which bear at least one chloro substituent.
In another preferred embodiment of the process according to the invention, step A) is carried out in the presence of an organic solvent, more preferably a high-boiling ether compound, even more preferably a high-boiling ether compound being diglyme or tetraglyme, most preferably diglyme.
According to the present invention, the term "organic solvent" refers to any organic compound which is in liquid state at room temperature, and which is suitable as a medium for conducting the cleavage reactions of step A) therein. Accordingly, the organic solvent is preferably inert to the cleavage reagents according to present invention, and to hydrogenation reagents such as metal hydrides under reaction conditions. Furthermore, the starting materials of the general formulae (I I), (I I I) and (IV) and the products of the general formula (I) are preferably soluble in the organic solvent or fully miscible, respectively.
Preferably, the organic solvent is selected from optionally substituted, preferably unsubstituted linear or cyclic aliphatic hydrocarbons, aromatic hydrocarbons or ether compounds, without being limited thereto.
Herein, the term "ether compound" shall mean any organic compound containing an ether group -0-, in particular of formula R1-O-R2, wherein Ri and R2, are independently selected from an organyl group R preferably having up to 20 carbon atoms and optionally one or more hetero atoms.
The organyl group R is selected from optionally substituted, preferably unsubstituted, alkyl, aryl, alkenyl, alkynyl, alkaryl, aralkyl, aralkenyl, aralkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, cycloaralkyl, cycloaralkenyl, cycloaralkynyl, alkoxy, aryloxy, and organosiloxy (cyclic and acyclic) groups, preferably alkyl, alkenyl and aryl groups.
Preferably, Ri and R2, are substituted or unsubstituted linear or branched alkyl groups or aryl groups, which may have further heteroatoms such as oxygen, nitrogen, or sulfur. In the case of cyclic ether compounds, Ri and R2 can constitute together an optionally substituted alkylene or arylene group, which may have further heteroatoms such as oxygen, nitrogen, or sulfur.
The ether compounds can be symmetrical or asymmetrical with respect to the substituents at the ether group -0-.
The term "ether compound" also comprises linear ether compounds in which more than one ether group may be included, forming a di- , tri- , oligo- or polyether compound, wherein Ri and R2 constitute organyl groups when they are terminal groups of the compounds, and alkylene or arylene groups when they are internal groups. Herein, a terminal group is defined as any group being linked to one oxygen atom which is part of an ether group, while an internal group is defined as any group linked to two oxygen atoms being a constituent of ether groups.
Preferred examples of such compounds are dimethoxy ethane, glycol diethers (glymes) , in particular diglyme or tetraglyme, without being limited thereto.
In the sense of the present invention, the term "high-boiling ether compound" is defined as an ether compound according to above definition with a boiling point at about 1 bar (ambient pressure) of preferably at least about 70 °C, more preferably at least about 85 °C, even more preferably at least about 100 °C, and most preferably at least about 120 °C. The application of high-boiling ethers in the present invention is favourable as it facilitates separation of the desired products of the general formula (I) from the reaction mixture containing the solvent and residual starting materials. The products of the general formula (I) in general have lower boiling points than the starting materials, and the boiling points of these products are also lower than the boiling point of high-boiling ethers of above definition. For instance, the boiling points of selected representative products of the general formula (I) are about 35 °C (Me2SiHCI) , about 41 °C (MeSiHC ) or about 57 °C (Me3SiCI), while representative higher-boiling ether compound diglyme has a boiling point of about 162 °C, and the boiling point of a mixture of methylchlorodisilanes principally consisting of isomers of trimethyltrichlorodisilane and dimethyltetrachlorodisilanes, which are respective substrates of the general formula (I I) is about 151 -158 °C. Application of higher-boiling ether compounds as solvents allows to utilize higher reaction temperatures and simplifies separation of the desired products from the reaction mixture by distillation. In a preferred embodiment of the process according to the invention, step A) is carried out in the presence of at least one compound of the formula R4PCI.
Herein, R is independently a hydrogen group or an organyl group, more preferably a hydrogen group, an aromatic group or an aliphatic hydrocarbon group.
Even more preferably, R is independently a hydrogen or an alkyl, cycloalkyl, aryl or alkaryl group of from 1 to 30 carbon atoms. R preferably includes alkyl having up to 16 carbon atoms such as methyl, butyl such as n-butyl, iso-butyl, hexyl such as n-hexyl, tetradecyl, such as n-tetradecyl, octyl, such as n-octyl. Preferably, the amount of the at least one compound of the formula R4PCI is in the range of about 0.01 to about 99.95 wt-% , more preferred about 0.1 to about 75 wt-% , more preferred about 0.1 to about 55 wt-% , even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% based on the total weight of the silane substrate. The term "weight-%" relates to the total weight of substrates of the general formulae (I I), (II I) and (IV) present in step A).
Compounds of the formula R4PCI are suitable cleavage compounds, acting as catalysts for the disilane cleavage and as hydrogen source, as they are able to cleave partially or fully hydrogenated disilanes at room temperature, highly methylated disilanes at room temperature to about 140 °C without major decomposition reactions, wherein oligosilanes are formed as side-products. At higher temperatures, for instance about 180 to about 220 °C and/or longer reaction times is was found that they react with the silane substrates such as disilanes, oligosilanes and carbodisilanes under formation of H-silanes. In particular, when n- Bu4PCI is used, H-silanes are generated by decomposition of n-Bu4PCI to n-Bu3P and formally butyl chloride with subsequent formation of 1-butene and HCI.
In another preferred embodiment of the process according to the invention, step A) is carried out in the presence of at least one cleavage compound of the formula R4PCI and at least one methylimidazole.
Preferably, each of the cleavage compounds is applied in an amount of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 75 wt-%, more preferred about 0.1 to about 55 wt-%, even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% is based on the total weight of the silane substrate.
Preferably, about equal weight amounts of at least one compound of the formula R4PCI and at least one methylimidazole are applied as cleavage reagent in step A).
Also preferably, the at least one methylimidazole is selected from the group of consisting of 1 -methylimidazole, 2-methylimidazole, 4-methylimidazole and 2,4-dimethylimidazole, most preferably it is 2-methylimidazole.
It was found that methylimidazole under certain conditions also act as a reactant in the cleavage reaction. In particular, in the reaction of 2-methylimidazole and CIMe2Si-SiMe2CI, 2-methylimidazole reacted with Me2SiCI2 to compound 1 (140-160°C) (see equation below). This molecule reacts at higher temperatures (>200°C) to compound 2, which could be characterized b X-ray diffractio
Figure imgf000022_0001
\ /
-Si— Si-CI CI Si- CI + : Si e2
Figure imgf000022_0002
Figure imgf000023_0001
1 2
These results explain why high amounts of Me2SiHCI are obtained using 2-methylimidazole in the cleavage reaction of step A).
Further preferably, the at least one compound of the formula R4PCI is selected from the group consisting of tetra(n-butyl)phosphonium chloride, methyltri(isobutyl)phosphonium chloride, tetra(n-octyl)phosphonium chloride, tri(n- butyl)tetradecylphosphonium chloride and octyltri(butyl)phosphonium chloride, most preferably it is tetra(n-butyl)phosphonium chloride (n-Bu4PCI) .
In yet another preferred embodiment of the process, step A) is carried out in the presence of n-Bu4PCI.
Preferably, n-Bu PCI is applied in an amount of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 75 wt-%, more preferred about 0.1 to about 55 wt-% , even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% is based on the total weight of the silane substrate.
In a further preferred embodiment of the process according to the invention, step A) is carried out in the presence of n-Bu PCI and 2-methylimidazole.
Preferably, each of the cleavage compounds is applied in an amount of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 75 wt-%, more preferred about 0.1 to about 55 wt-%, even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% is based on the total weight of the silane substrate.
Generally preferably, about equal weight amounts of n-Bu PCI and 2-methylimidazole are applied as cleavage reagent in step A) . In another preferred embodiment of the process according to the invention, step A) is carried out in the presence of at least one compound of the formula R4PCI and at least one metal hydride, preferably lithium hydride. Preferably, the amount of the at least one metal hydride is in the range of about 1 mol-% to about 600 mol-%, preferably about 1 to about 400 mol-%, more preferably about 1 to about 200 mol-%, most preferably about 25 to about 150 mol-% , based on the total molar amount of the chlorine atoms present in silane substrate compounds, while the amount of the at least one compound of the formula R4PCI is in the range from about 0.01 to about 99.95 weight-% , more preferably from about 0.1 to about 60 weight-%, even more preferably from about 1 to about 25 weight-%, and most preferably from about 1 to about 5 weight-% based on the total amount of the silane substrate.
By the presence of at least one metal hydride in step A) , the substrates of the general formulae (I I), (I I I) and (IV) are partially or completely hydrogenated before or during the cleavage reaction takes place.
The resulting partially or fully hydrogenated substrates of the general formulae (I I) , (I II) and (IV) are more readily cleavable by cleavage reagents of the formula RPCI4 than their analogues prior to hydrogenation. Accordingly, lower reaction temperatures can be applied for cleavage, and the percentage of hydrogen substituents in the resulting silanes of the general formula (I) is increased by such reaction conditions. The content of hydrogen substituents in the products of the general formula (I) is also increased by hydrogenation of cleavage products of the general formula (I) bearing chloro substituents, which is effected by the presence of a metal hydride in step A) .
In yet another preferred embodiment of the process according to the invention step A) is carried out in the presence of n-Bu PCI and lithium hydride. Herein, the presence of n-Bu PCI does not preclude the presence of further cleavage reagents in the reaction mixture of step A) , and the presence of lithium hydride does not preclude the presence of further hydrogenation reagents in the reaction mixture of step A).
In a preferred embodiment of the process according to the invention, step A) is carried out in the presence of about 1 to about 200, preferably about 5 to about 100 mol-% n-Bu PCI in relation to the amount of the silane substrate compounds of the general formulae (I I), (I II) and (IV) and about 1 to about 600 mol-%, preferably about 1 to about 400 mol-% LiH in relation to the chlorine atoms present in the silane substrate compounds of the general formulae (I I) , (I I I) and (IV) . Herein, the term "amount of silane substrate compounds" refers to the combined molar amounts of all disilanes of the general formula (I I) , oligosilanes of the general formula (I I I) or carbodisilanes of the general formula (IV) . In the determination of the molar amount these compounds are considered regardless if they are submitted as a part of a mixture comprising other silane compounds, in particular disilanes and carbodisilanes, which do not fall under the general formulae (I I), (I II) or (IV) .
Preferably, the amount of lithium hydride is in the range of from about 1 to about 600 mol-% , more preferably from about 10 to about 350, even more preferably from about 25 to about 200, and most preferably from about 25 to about 100 mol-% based on the molar amount of the chlorine atoms present in the silane substrate compounds of the general formulae (I I) , (II I) and (IV) , while the amount of n-Bu4PCI is preferably in the range from about 0.01 to about 99.95 wt-% more preferably from about 0.1 to about 60 wt-%, even more preferably from about 1 to about 25 wt-%, and most preferably from about 1 to about 10 wt-% based on the total weight of the silane substrate.
In a further preferred embodiment of the process according to the invention, step A) is conducted at a temperature of about 0 °C to about 300 °C, more preferably 20 °C to 280 °C. More preferably the temperature is at least about 100 °C, more preferably at least about 150 °C, more preferably at least 200 °C and most preferably at least 220 °C.
The reaction time is preferably at least about 4 hours, more preferably at least about 6 hours, more preferably at least about 8 hours and most preferably at least about 10 hours.
Reaction temperature and reaction time of the cleavage reaction are suitably selected for a certain silane substrate and cleavage compound such that at least one of the following parameters is met:
(i) until at least about 50 mol-% of the cleavage compound based on the initial molar amount of the cleavage compound is reacted, and/or (ii) until the ratio of the total of the produced monosilanes of the general formula (I) wherein y = 1 to 3 is at least about 40 mol-%, preferably at least about 50 mol-%, based on the total molar amount of the monosilanes of the general formula (I), and/or
(iii) until the ratio of Me2SiHCI is at least about 20 mol-%, preferably at least about 30 mol-%, based on the total amount of the monosilanes of the general formula (I).
According to the invention, the reaction temperature in step A) is the temperature of the reaction mixture, i.e. the temperature measured inside the reaction vessel in which the reaction is conducted.
In another preferred embodiment of the process according to the invention, step A) is carried out using at least one quaternary Group 15 onium compound represented by the formula R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 220 °C, and even more preferably at about 80 to about 160 °C.
In yet another preferred embodiment of the process according to the invention, step A) is carried out using at least one compound selected from heterocyclic amines and heterocyclic ammonium halides as cleavage compound, at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 220 °C, even more preferably at about 100 to about 220 °C, and most preferably at about 140 °C to about 220 °C.
In still another preferred embodiment of the process according to the invention, step A) is carried out using at least one quaternary Group 15 onium compound represented by the formula R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, and at least one compound selected from heterocyclic amines and heterocyclic ammonium halides as cleavage compound, at a temperature of about 0 °C to about 300 °C, more preferably about 50°C to about 220 °C, even more preferably at about 100 to about 200 °C, and most preferably at about 120 °C to about 180 °C.
Herein, the reaction temperature in step A) according to the invention is the temperature of the reaction mixture, i.e. the temperature measured inside the reaction vessel in which the reaction is conducted. Preferably, the reaction vessel can be an ampoule, a sealed tube, a flask or any kind of chemical reactor, without being limited thereto.
Further preferably, the reaction step A) is carried out in a suitably sized reactor made of materials, such as glass or Hastelloy C, which are resistant to corrosion by chlorides. A means of vigorous agitation is provided to disperse or dissolve the cleavage reagent or mixtures of cleavage reagent and metal hydride in the solvent.
In another preferred embodiment of the process according to the invention, step A) is conducted at a pressure of about 0.1 bar to about 30 bar, more preferably at about 1 bar to about 20 bar, most preferably at about 1 bar to about 10 bar.
The indicated pressure ranges refer to the pressure measured inside the reaction vessel used when conducting reaction step A).
In yet another preferred embodiment of the process according to the invention in the step A) the weight ratio of the silane substrates to the organic solvent is in the range of about 1 to about 100 wt-%, more preferably in the range of about 10 to about 80 wt-%, even more preferably about 20 to about 60 wt-%, most preferably about 30 to about 50 wt-% based on the weight of the organic solvent and silane substrate.
In a preferred embodiment of the process according to the invention in the step A) the weight ratio of the cleavage compound to the organic solvent is in the range of about 0.01 to about 100 wt-%, more preferably in the range of about 0.1 to about 50 wt-%, even more preferably about 0.5 to about 20 wt-%, most preferably about 1 to about 10 wt-% based on the weight of the organic solvent and cleavage compound.
Step A) can be done also solvent free. In this case the weight-percentages of the silane substrates to the organic solvent and of the cleavage compound to the organic solvent as indicated before amount to about 100 wt-%.
In a further preferred embodiment of the process according to the invention, the monosilanes of the formula (I) are selected from the group consisting of Me2SiHCI, Me2SiH2, Me3SiCI, Me2SiCI2, Me3SiH, MeSihh, MeSiHC , MeSiH2CI, and MeSiC . Preferably, the methylmonosilanes of the formula (I) are selected from the group consisting of Me2SiHCI, MeSiHC , MeSiH2CI, Me3SiCI, Me3SiH, Me2SiH2, MeSiH3 and Me2SiCI2.
In yet another preferred embodiment of the process according to the invention, the monosilanes of the formula (I) are selected from the group consisting of Me2SiHCI, Me3SiCI, and MeSiHCb.
In a preferred embodiment of the process according to the invention, dimethylchloromonosilane Me2SiHCI is formed by submitting a substrate selected from the group consisting of CIMe2Si-SiMe2CI, CIMe2Si-SiMeCI2, Me3Si-SiMe2CI, HMe2Si-SiMe2H, HMe2Si-SiMeH2, Me3Si-SiMe2H, CIMe2Si-SiMe2H, CIMe2Si-SiMeH2, HMe2Si-SiMeCI2, CIMe2Si-CH2-SiMeCI2, CI2MeSi-CH2-SiMeCI2 CIMe2Si-CH2-SiMe2CI, Me3Si-CH2-SiMe2CI, CIMe2Si-SiMe2-SiMe2CI, CIMe2Si-SiMe2-SiMe2-SiMe2CI or (CIMe2Si)3SiMe to the cleavage reactions of step A).
Therein, each of the above-stated substrates may be submitted to the reaction conditions as single substrate, in a mixture with other compounds of the above-stated compounds, or in a mixture with other substrates of the general formulae (II), (III) or (IV). In another preferred embodiment of the process according to the invention, trimethylchlorosilane Me3SiCI is formed by submitting a substrate selected from the group consisting of Me3Si-SiMe2CI, Me3Si-SiMeCI2, Me3Si-SiMe2H, Me3Si-CH2-SiMe2CI, CIMe2Si- CH2-SiMe2CI, CIMe2Si-CH2-SiMeCI2 Me3Si-CH2-SiMe3 or Me3Si-CH2-SiMeCI2 to the cleavage reactions of step A).
Therein, each of the above-stated substrates may be submitted to the reaction conditions as single substrate, in a mixture with other compounds of the above-stated compounds, or in a mixture with other substrates of the general formulae (II), (III) or (IV). In a further preferred embodiment of the process according to the invention, methyldichloromonosilane MeSiHCb is formed by submitting a substrate selected from the group consisting of CbMeSi-SiMeCb, CI2MeSi-SiMe2CI, CI2MeSi-SiMe3, HCIMeSi-SiMeH2, HCIMeSi-SiMeCIH, HCIMeSi-SiMeCb, CI2MeSi-SiMeH2, CIHMeSi-SiMe2CI, CI2MeSi-SiMe2H, CIHMeSi-SiMe2H, CI2MeSi-CH2-SiMeCb, CIMe2Si-CH2-SiMeCb, Me3Si-CH2-SiMeCb, (CI2MeSi)2SiMeCI, (CI2MeSi)3SiMe, (CI2MeSi)2SiMe-SiCIMe-SiCI2Me, [(CI2MeSi)2SiMe]2, [(CI2MeSi)2SiMe]2SiCIMe or (CI2MeSi)2SiMe-SiMe2CI to the cleavage reactions of step A). Therein, each of the above-stated substrates may be submitted to the reaction conditions as single substrate, in a mixture with other compounds of the above-stated compounds, or in a mixture with other substrates of the general formula (II), (III) or (IV).
In a preferred embodiment of the process according to the invention, the step B) of separating the resulting monosilanes of the formula (I) is carried out by distillation, low temperature condensation, or a combination thereof. The term "distillation" in the sense of the present invention relates to any process for separating components or substances from a liquid mixture by selective evaporation and condensation. Therein, distillation may result in practically complete separation of the constituents of a mixture, thus leading to the isolation of nearly pure compounds, or it may be a partial separation that increases the concentration of selected constituents of the mixture in the distillate when compared to the mixture submitted to distillation.
Preferably, the distillation processes which may constitute separation step B) can be simple distillation, fractional distillation, vacuum distillation, short path distillation or any other kind of distillation known to the skilled person.
Also preferably, the step B) of separating the monosilanes of the formula (I) according to the invention can comprise one or more batch distillation steps, or can comprise a continuous distillation process. Further preferably, the term "low temperature condensation" may comprise separation or enrichment of one or more compounds of the general formula (I) from the reaction mixture by volatilization from the reaction vessel and condensation as a liquid and/or solid in a refrigerated vessel from which it can be subsequently recovered by distillation, or by solution in an ether solvent. Alternatively, the monosilanes can be absorbed in an ether solvent contained in a refrigerated vessel.
In a further preferred embodiment of the process according to the invention, the hydrogenation of the silane substrates prior to step A) is carried out using n-Bu3SnH for partial hydrogenation, or LiAlhU for complete hydrogenation. In another preferred embodiment of the process according to the invention, the silane substrates comprising the silane substrate compounds of the general formulae (II), (III), and (IV), and the mixtures thereof are residues of the Rochow-Muller Direct Process (DPR). The primary commercial method to prepare alkylhalosilanes and arylhalosilanes is through the Rochow-Muller Direct Process (also called Direct Synthesis or Direct Reaction), in which copper-activated silicon is reacted with the corresponding organohalide, in particular methyl chloride, in a gas-solid or slurry-phase reactor. Gaseous products and unreacted organohalide, along with fine particulates, are continuously removed from the reactor. Hot effluent exiting from the reactor comprises a mixture of copper, metal halides, silicon, silicides, carbon, gaseous organohalide, organohalosilanes, organohalodisilanes, carbodisilanes and hydrocarbons. Typically this mixture is first subjected to gas-solid separation in cyclones and filters. Then the gaseous mixture and ultrafine solids are condensed in a settler or slurry tank from which the organohalide, organohalosilanes, hydrocarbons and a portion of organohalodisilanes and carbodisilanes are evaporated and sent to fractional distillation to recover the organohalosilane monomers. The solids accumulated in the settler along with the less volatile silicon-containing compounds are purged periodically and sent to waste disposal or to secondary treatment. Organohalodisilanes and carbodisilanes left in the post-distillation residues are also fed to hydrochlorination. Organohalodisilanes, organohalopolysilanes and carbodisilanes, related siloxanes and hydrocarbons, either in the post-distillation residues or in the slurry purged from the reactor, boil above organohalosilane monomers. Collectively they are referred to as Direct Process Residue (DPR). The terms higher boilers, high-boiling residue and disilane fraction are also used interchangeably with DPR.
By the process according to the invention, disilanes, in particular, methylchlorodisilanes of the general formula (II), oligosilanes of the general formula (III) and carbodisilanes of the general formula (IV), which are constituents of the side-products of the Rochow-Muller Direct Process (DPR), can be transformed to monosilanes of the general formula (I) via cleavage reactions, optionally involving hydrogenation of the substrates of the formulae (II), (III), and (IV) or the products (I).
In yet another preferred embodiment of the process according to the invention, the process is performed under inert conditions. In the sense of present invention, the term "performed under inert conditions" means that the process is partially or completely carried out under the exclusion of surrounding air, in particular of moisture and oxygen. In order to exclude ambient air from the reaction mixture and the reaction products, closed reaction vessels, reduced pressure and/or inert gases, in particular nitrogen or argon, or combinations of such means may be used. Preferred embodiments of the invention:
In the following the preferred embodiments of the invention are shown:
1 . Process for the manufacture of monosilanes of the general formula (I):
MexSiHyClz (I),
wherein
x = O to 3,
y = 0 to 3, preferably 1 to 3, more preferably 1 or 2,
z = 0 to 4 and
x + y + z = 4,
and mixtures thereof,
comprising:
A) the step of subjecting a silane substrate comprising one or more silane substrate compounds selected from the group of
a) one or more disilanes of the general formula (II)
MemSi2HnClo (II)
wherein
m = 0 to 6,
n = 0 to 6, preferably 0 to 4,
o = 0 to 6 and
m + n + o = 6,
b) one or more linear or branched oligosilanes of the general formula (III)
MepSiqHrCIs (II I),
wherein
q = 3 to 7
p = q to (2q + 2)
r, s = 0 to (q + 2)
r + s = (2q + 2) - p
and wherein each Si atom preferably bears at least one methyl group, and c) one or more carbodisilanes of the general formula (IV)
(MeaSiHbCle)-CH2-(MecSiHdClf) (IV)
wherein a, c are independently of each other 1 to 3,
b, d are independently from each other 0 to 2
e, f are independently from each other 0 to 2,
a + b + e = 3,
c + d + f = 3,
and mixtures containing compounds of the general formulae (II), (III) and (IV), to the cleavage reaction of the silicon-silicon bond(s) in the silane substrates of the general formulae (II) and (III) and the silicon-carbon bond(s) of the carbodisilanes of the general formula (IV),
to the reaction with at least one compound (cleavage compound) selected from the group consisting of:
- a quaternary Group 15 onium compound R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I ,
- a heterocyclic amine,
- a heterocyclic ammonium halide,
- a mixture of R3P and RX, wherein R is as defined above, and X is as defined above, and
mixtures of the above-mentioned compounds,
(i) until at least about 50 mol-% of the cleavage compound based on the initial molar amount of the cleavage compound is reacted, and/or
(ii) until the ratio of the total of the produced monosilanes of the general formula (I) wherein y = 1 to 3 is at least about 40 mol-%, preferably at least about 50 mol-%, based on the total molar amount of the monosilanes of the general formula (I), and/or
(iii) until the ratio of Me2SiHCI is at least about 20 mol-%, preferably at least about 30 mol-%, based on the total amount of the monosilanes of the general formula (I), and
B) optionally a step of separating the resulting monosilanes of the general formula (I). 2. Process according to embodiment 1 , wherein the reaction in step A) is carried out for more than about 4 hours and at a temperature of at least about 200 °C, or the reaction in step A) is carried out for more than about 10 hours preferably, at a temperature of more than about 100 °C.
3. Process according to embodiments 1 or 2, which is carried out without the supply of hydrogen (H2). 4. Process according to any of embodiments 1 to 3, wherein the silane substrate is consisting of one or more silane substrate compounds selected from the group consisting of the disilanes of the general formula (II), linear or branched oligosilanes of the general formula (II I) and the carbodisilanes of the general formula (IV).
5. Process according to any of the previous embodiments, wherein the quaternary Group 15 onium compound is represented by the formula R4PCI, wherein R is independently a hydrogen group or an organyl group, more preferably a hydrogen group, an aromatic group or an aliphatic hydrocarbon group.
6. Process according to embodiment 5, wherein the compounds of formula R4PCI are formed in situ from compounds of formula R3P and RCI.
7. Process according to any of the previous embodiments, wherein step A) is carried out by subjecting the silane substrate to the cleavage reaction of step A) in the presence of a hydrogen halide HX, wherein X is selected from the group consisting of F, CI, Br and I.
8. Process according to any of the previous embodiments, wherein step A) is carried out in the presence of at least one metal hydride, preferably at least one metal hydride selected from the group of alkali metal hydrides and alkaline earth metal hydrides, more preferably at least one alkali metal hydride, and most preferably lithium hydride.
9. Process according to any of the previous embodiments, wherein the silane substrate, comprises at least one of the compounds selected from the group consisting of
Si2CI6, C MeSi-SiMeCIH, HCIMeSi-SiMeCIH, CI2MeSi-SiMeH2, HCIMeSi-SiMeH2, CIMe2Si- SiMeCIH, CI2MeSi-SiMe2H, CIMe2Si-SiMeH2, HMe2Si-SiMeCIH, CIMe2Si-SiMe2CI, Me3Si- SiMe2CI, CIMe2Si-SiMe2H, Me3Si-SiMe2H, HMe2Si-SiMe2H, H2MeSi-SiMeH2, HMe2Si- SiMeH2, CI2MeSi-SiMeCI2, CIMe2Si-SiMeCI2, Me3Si-SiMeCI2, CI2MeSi-CH2-SiMeCI2, CIMe2Si- CH2-SiMeCI2, CIMe2Si-CH2-SiMe2CI, Me3Si-CH2-SiMeCI2, Me3Si-CH2-SiMe2CI, Me3Si-CH2- SiMe3, CIMe2Si-SiMe2-SiMe2CI, CIMe2Si-SiMe2-SiMe2-SiMe2CI, (CIMe2Si)3SiMe, CIMe2Si- SiMe2-SiMe2H, (CI2MeSi)2SiMeCI, (CI2MeSi)3SiMe, (CI2MeSi)2SiMe-SiCIMe-SiCI2Me, [(CI2MeSi)2SiMe]2, [(CI2MeSi)2SiMe]2SiCIMe, and (CI2MeSi)2SiMe-SiMe2CI, and mixtures thereof.
10. Process according to any of the previous embodiments, wherein the molar ratio of the cleavage compound used in step A) to the silane substrate compounds of the general formulae (II), (III) and (IV) is in the range of about 0.0001 to about 100 mol-%, more preferred 0.001 to 50 mol-%, more preferred 0.001 to 25 mol-%, even more preferred 0.01 to 10 mol- %, and most preferably 0.01 to 0.5 mol-% based on the molar amount of the silane substrate compounds.
1 1 . Process according to any of the previous embodiments, wherein the weight ratio of the cleavage compound used in step A) to the silane substrate is in the range of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 75 wt-%, more preferred about 0.1 to about 55 wt-%, even more preferred about 1 to about 25 wt-% and most preferably about 2 to about 10 wt-% is based on the total weight of the silane substrate.
12. Process according to any of the previous embodiments, wherein the amount of the metal hydride in step A) in relation to the silane substrate compounds of the general formulae (II), (II I) and (IV) is in the range of about 1 mol-% to about 600 mol-% , preferably about 1 to about 400 mol-%, more preferably about 1 to about 200 mol-%, most preferably about 25 to about 150 mol-% , based on the total molar amount of the chlorine atoms present in silane substrate compounds.
13. Process according to any of the previous embodiments, wherein the silane substrates used in step A) are submitted to a hydrogenation step before the cleavage reaction of the silicon-silicon bond(s) in the silane substrates of the general formulae (I I) and (I I I) and/or the silicon-carbon bond(s) of the carbodisilanes of the general formula (IV) is carried out, wherein chlorine atoms contained in the silane substrates are partially or completely exchanged by hydrogen atoms.
14. Process according to any of the previous embodiments, wherein the hydrogenation of the silane substrates prior to step A) is carried out with a hydride donor selected from the group of metal hydrides, preferably complex metal hydrides and organometallic hydride reagents such as LiAIH4, n-Bu3SnH, NaBH4, /'-BU2AIH or sodium bis(2-methoxyethoxy) aluminumhydride.
15. Process according to any of the previous embodiments, wherein step A) is carried out in the presence of an organic solvent, preferably an high-boiling ether compound, more preferably diglyme or tetraglyme, most preferably diglyme.
16. Process according to the previous embodiments, wherein step A) is carried out in the presence of at least one compound of the formula R4PCI.
17. Process according to the previous embodiments, wherein step A) is carried out in the presence of at least one compound of the formula R4PCI and at least one methylimidazole.
18. Process according to any of the previous embodiments, wherein step A) is carried out in the presence of n-Bu4PCI.
19. Process according to any of the previous embodiments, wherein step A) is carried out in the presence of n-Bu4PCI and 2-methylimidazole.
20. Process according to the previous embodiments, wherein step A) is carried out in the presence of at least one compound of the formula R4PCI and at least one metal hydride, preferably lithium hydride.
21 . Process according to any of the previous embodiments, wherein step A) is carried out in the presence of n-Bu4PCI and lithium hydride. 22. Process according to any of the previous embodiments, wherein step A) is carried out in the presence of about 0.01 to about 99.95 wt-%, more preferred about 0.1 to about 75 wt- %, more preferred about 0.1 to about 55 wt-%, even more preferred about 1 to about 25 wt- % and most preferably about 2 to about 10 wt-% n-Bu4PCI wherein the weight percentage wt-% is based on the total weight of the silane substrate and about 1 mol-% to about 600 mol-%, preferably about 1 to about 400 mol-%, more preferably about 1 to about 200 mol-%, most preferably about 25 to about 150 mol-% LiH based on the total molar amount of the chlorine atoms present in silane substrate compounds.
23. Process according to any of the previous embodiments, wherein the step A) is conducted at a temperature of about 0 °C to about 300 °C, preferably at about 20 °C to about
220 °C.
24. Process according to any of the previous embodiments, wherein step A) is carried out using at least one cleavage compound selected from quaternary Group 15 onium compounds represented by the formula R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I , at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 220 °C, and even more preferably at about 80 to about 160 °C.
25. Process according to any of the previous embodiments, wherein step A) is carried out using at least one cleavage compound selected from heterocyclic amines and heterocyclic ammonium halides, at a temperature of about 0 °C to about 300 °C, more preferably about 20 °C to about 250 °C, even more preferably at about 100 to about 220 °C, and most preferably at about 140 °C to about 220 °C.
26. Process according to any of the previous embodiments, wherein step A) is carried out using at least one cleavage compound selected from quaternary Group 15 onium compounds represented by the formula R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, and at least one cleavage compound selected from heterocyclic amines and heterocyclic ammonium halides, at a temperature of about 0 °C to about 300 °C, more preferably about 50 °C to about 250 °C, even more preferably at about 100 to 220 °C, and most preferably at 150 °C to 220 °C.
27. Process according to any of the previous embodiments, wherein step A) is carried out using at least one cleavage compound selected from quaternary Group 15 onium compounds represented by the formula R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, and at least one cleavage compound selected from heterocyclic amines and heterocyclic ammonium halides, at a temperature of about 0 °C to about 300 °C, more preferably about 50 °C to about 220 °C, even more preferably at about 100 to about 200 °C, and most preferably at about 120 °C to about 180
°C.
28. Process according to any of the previous embodiments, wherein the step A) is conducted at a pressure of about 0.1 bar to about 30 bar, more preferably at about 1 bar to about 20 bar, most preferably at about 1 bar to about 10 bar.
29. Process according to any of the previous embodiments, wherein in the step A) the weight ratio of the silane substrate to the organic solvent is in the range of about 1 to about 100 wt-%, more preferably in the range of about 10 to about 80 wt-%, even more preferably about 20 to 60 about wt-%, most preferably about 30 to about 50 wt-% based on the weight of the organic solvent and silane substrate.
30. Process according to any of the previous embodiments, wherein in the step A) the weight ratio of the cleavage compound to the organic solvent is in the range of about 0.01 to about 100 wt-%, more preferably in the range of about 0.1 to about 50 wt-%, even more preferably about 0.5 to about 20 wt-%, most preferably about 1 to about 10 wt-% based on the weight of the organic solvent and cleavage compound.
31 . Process according to any of the previous embodiments, wherein the monosilanes of the formula (I) are selected from the group consisting of Me2SiHCI, Me2SiH2, Me3SiCI, Me2SiCI2, Me3SiH, MeSih , MeSiHCI2, MeSiH2CI, and MeSiCI3.
32. Process according to any of the previous embodiments, wherein the monosilanes of the formula (I) are selected from the group consisting of Me2SiHCI, Me3SiCI, and MeSiHCI2.
33. Process according to any of the previous embodiments, wherein dimethylchloromonosilane Me2SiHCI is formed by submitting a silane substrate selected from the group consisting of CIMe2Si-SiMe2CI, CIMe2Si-SiMeCI2, Me3Si-SiMe2CI, HMe2Si-SiMe2H, HMe2Si-SiMeH2, Me3Si-SiMe2H, CIMe2Si-SiMe2H, CIMe2Si-SiMeH2, HMe2Si-SiMeCI2, CI2MeSi-CH2-SiMeCI2 CIMe2Si-CH2-SiMeCI2, CIMe2Si-CH2-SiMe2CI, Me3Si-CH2-SiMe2CI, CIMe2Si-SiMe2-SiMe2CI, CIMe2Si-SiMe2-SiMe2-SiMe2CI, (CIMe2Si)3SiMe and mixtures thereof to the cleavage reactions of step A).
34. Process according to any of the previous embodiments, wherein the trimethylchlorosilane Me3SiCI is formed by submitting a silane substrate selected from the group consisting of Me3Si-SiMe2CI, Me3Si-SiMeCI2, Me3Si-SiMe2H, Me3Si-CH2-SiMe2CI, CIMe2Si-CH2-SiMe2CI, CIMe2Si-CH2-SiMeCI2, Me3Si-CH2-SiMe3, Me3Si-CH2-SiMeCI2 and mixtures thereof to the cleavage reactions of step A).
35. Process according to any of the previous embodiments, wherein the methyldichloromonosilane MeSiHCI2 is formed by submitting a silane substrate selected from the group consisting of CI2MeSi-SiMeCI2, CI2MeSi-SiMe2CI, CI2MeSi-SiMe3, HCIMeSi- SiMeH2, HCIMeSi-SiMeCIH, HCIMeSi-SiMeC , CI2MeSi-SiMeH2, CIHMeSi-SiMe2CI, CI2MeSi-SiMe2H, CIHMeSi-SiMe2H, CI2MeSi-CH2-SiMeCI2, CIMe2Si-CH2-SiMeCI2, Me3Si- CH2-SiMeCI2, (CI2MeSi)2SiMeCI, (CI2MeSi)3SiMe, (CI2MeSi)2SiMe-SiCIMe-SiCI2Me, [(CI2MeSi)2SiMe]2, [(CI2MeSi)2SiMe]2SiCIMe, (CI2MeSi)2SiMe-SiMe2CI and mixtures thereof to the cleavage reactions of step A).
36. Process according to any of the previous embodiments, wherein the step of separating the resulting monosilanes of the formula (I) is carried out by distillation, low temperature condensation or a combination thereof.
37. Process according to any of the previous embodiments, wherein the hydrogenation of the silane substrates prior to step A) is carried out using n-Bu3SnH for partial hydrogenation and UAIH4 for complete hydrogenation.
38. Process according to any of the previous embodiments, wherein the silane substrates of the general formulae (II) and (III), and the carbodisilane substrates of the general formula (IV), or the mixtures thereof are residues of the Rochow-Muller Direct Process (DPR).
39. Process according to any of the previous embodiments, wherein the process is performed under inert conditions.
40. Monosilanes of the general formula (I) as defined above, as obtainable by the process according to any of the previous embodiments.
41 . Compositions comprising at least one monosilane of the general formula (I) as defined above, as obtainable by the process according to any of the previous embodiments.
EXAMPLES
The present invention is further illustrated by the following examples, without being limited thereto. General
The first section (Examples 1-14) is directed at detailed investigations of the performance of the cleavage compounds n-Bu4PCI, 2-methylimidazole (2-MIA) and derivatives thereof. In particular, model compounds such as CIMe2Si-SiMe2CI were applied to study the influence of reaction temperature and reaction times. It was demonstrated that both cleavage compounds act as catalysts at lower reaction temperatures, while they act as reaction partners at high temperatures (in particular at about more than 180 °C, in particular at about 220 °C) and thus generate H-silanes (Me2SiHCI, MeSiHCI2...) in high yields. At low temperatures, 2- methylimidazole (2-MIA) forms oligosilanes and cleaves these compounds at higher temperatures under decomposition of the cleavage compound. n-Bu4PCI already cleaves disilane substrates at low temperatures, such as r.t. to about 140 °C and also forms oligosilanes. At higher temperatures (about 180 to about 220 °C) H-silanes are formed. By decomposition of n-Bu4PCI to n-Bu3P and formally butyl chloride with subsequent formation of HCI and 1-butene H-silanes are generated.
The second section (Examples 15-27) is directed at the hydrogenation of the disilanes/monosilanes and cleavage of hydrogenated disilanes with the cleavage compounds (n-Bu4PCI and 2-MIA). As disilanes form a Si-H-fraction of only about 50 mol% with both of the cleavage compounds, the aim of the experiments of the second section is to obtain higher yields of the H-substituted monosilanes. In the first place, this can be achieved by Cl- H-exchange of the disilanes and subsequent cleavage. Herein, n-Bu4PCI is a suitable catalyst, as it is capable of cleaving partially and fully hydrogenated disilanes to monosilanes to full extent already at room temperature. At this, only a minor amount (about 5mol%) of the catalyst is decomposed in the case of highly methylated and hydrogenated disilanes, as the higher the degree of methylation of the disilanes is, the higher temperatures are required for cleavage.
Identification of products
Products were analyzed by 1H, 29Si and 1H-29Si-HSQC NMR spectroscopy. The spectra were recorded on a Bruker AV-500 spectrometer equipped with a Prodigy BBO 500 S1 probe. 1H- NMR spectra were calibrated to the residual solvent proton resonance ([D6]benzene <5H = 7.16 ppm). Product identification was additionally supported by GC-MS analyses and verified identification of the main products. GC-MS analyses were measured with a Thermo Scientific Trace GC Ultra coupled with an ITQ 900MS mass spectrometer. The stationary phase (Machery-Nagel PERMABOND Silane) had a length of 50 m with an inner diameter of 0.32 mm. 1 μΙ of analyte solution was injected, 1/25 thereof was transferred onto the column with a flow rate of 1.7 mL/min carried by Helium gas. The temperature of the column was first kept at 50 °C for 10 minutes. Temperature was then elevated at a rate of 20 °C/min up to 250 °C and held at that temperature for another 20 minutes. After exiting the column, substances were ionized with 70 eV and cationic fragments were measured within a range of 34 - 600 m/z (mass per charge). Product mixtures were diluted with benzene prior to the measurement.
The characteristic 29Si-NMR chemical shifts and coupling constant 1J{29Si-1H} for the starting materials and the products formed are listed in Table 1.
Table 1 : identification of starting materials and products
Figure imgf000039_0001
23 MesSi-Ch -SiMeC 30.6 -0.5 - -
24 Me3Si-CH2-SiMe2CI 30.0 -0.4 - -
25 MesSi-Ch -SiMes -0.5
26 CIMe2Si-SiMe2-SiMe2CI 25.4 -43.9 -
27 CIMe2Si- SiMe2-SiMe2-SiMe2CI 27.1 -43.2 -
28 (CIMe2Si)3-SiMe 26.9 -76.2 -
29 CIMe2Si-SiMe2SiMe2H 27.0 -45.6 -37.8 183.4
30 (CI2MeSi)2SiMeCI 24.1 -5.3 -
31 (Cl2MeSi)3SiMe 30.6 -64.3 -
32 ( C I2 M eS i )2S i M e-S iC I M e-S i C I2 M e 32.3 -64.0 4.5 25.3 -
33 [(CI2MeSi)2SiMe]2 33.2 -63.2 -
34 [(CI2MeSi)2SiMe]2SiCIMe 32.1 -60.4 13.1 -
35 (Cl2MeSi)2SiMe-SiMe2CI 33.9 -66.9 23.8 -
36 C Si-SiC -6.5 -
37 SiC -19.0 -
38 C MeSi-SiMeCIH 23.8 -6.7 - 227.4
39 HCIMeSi-SiMeCIH -3.9 -4.3 21 1.7 -
40 CI2MeSi-SiMeH2 32.1 -61.4 - 196.7
41 HCIMeSi-SiMeh 0.6 -64.7 215.0 203.3
42 CIMe2Si-SiMeCIH 17.6 -3.7 - 221.3
43 Cl2MeSi-SiMe2H 33.8 -35.5 - 191.3
44 CIMe2Si-SiMeH2 22.6 -64.6 - 195.6
45 HMe2Si-SiMeCIH 1.83 -38.2 181.3 198.4
Example 1 :
Cleavage reactions of perchlorinated and methylated chlorodisilanes with n-Bu4PCI (5 w%) and 2-methylimidazole (2-MIA, 5 w%) as catalyst in a sealed glass ampoule at 175 °C for 2.5 h. The starting compounds and reaction products are listed in Table 2.
Table 2 (Reference exam
Figure imgf000041_0001
For comparison CIMe2Si-SiMe2CI (1 , 585 mg) reacted at 175 °C with n-Bu4PCI (5 w%) and 2- methylimidazole (2-MIA, 5 w%) as catalyst. Reactions were performed in a sealed NMR tube for 2.5 h, to give mostly the monosilanes Me2SiCI2 (51 mol%) and small amounts of Me2SiHCI (4mol%). Additionally, tri- and tetrasilanes Si3Me6CI2 and Si4Me8CI2 were formed in a molar ratio of 14mol% to 8mol%. All products formed after 2.5 h reaction time are listed in Table 3. Prolonged heating of the samples for 89 h cleaved the oligosilanes too, finally giving the monosilanes 8 (57mol%), 5 (34mol%) and 7 (7mol%). Disilane 1 remained in the product mixture in small amounts (2mol%) (Table 3).
Table 3
Figure imgf000041_0002
(*Reference example)
After 89 h reaction time at 175 °C Me3Si-SiMe2CI (2) gave 7 (85mol%), Me3SiH (9, 1 1 mol%), and 2 (4mol%), besides traces of different oligosilanes. Example 2:
A mixture of silanes, composed of compounds listed in Table 4 (13.1 g), Table 5 (14.1 g) and Table 6 (12.5 g), was reacted with the catalyst mixture (n-Bu4PCI 5 w% and 2-MIA 5 w%) in a 250 ml flask, equipped with a thermometer, Vigreux column and a distillation condenser. The reaction mixture was heated to 145 °C while volatile cleavage products were continuously distilled off and collected at -20 °C. After 5 h the reaction was stopped to give monosilanes 19 (44mol%) and 8 (31 mol%) as listed in Table 7. The residue mainly consisted of disilanes 1 and 2 and traces of 8. After 13 h reaction time the resulting product mixture was 19 (36mol%), 8 (33mol%), 17 (29mol%) and 7 (2mol%). The residue mainly consisted of disilanes 1 , 2, Me3Si-SiMe3, and carbodisilanes as well as traces of monosilane 8.
Table 4
Figure imgf000042_0001
Table 5
Figure imgf000042_0002
Table 6
Figure imgf000043_0001
The experiment clearly proved that cleavage of disilanes and carbodisilanes becomes increasingly difficult with increasing degree of methylation at the silicon skeletons. Prolonged reaction time accelerated cleavage of disilane 1 that, after 5 h, still dominated over 2 in the residue; after 13 h disilane 2 remained as main component in the reaction residue. H- substituted organosilane 17 was increasingly formed with prolonged reaction times but showed that highly chlorinated disilanes require shorter reaction times/temperatures for cleavage into hydrido substituted monosilanes. In summary, with prolonged reaction times the mixture was transferred into monosilanes nearly quantitatively, only Me3Si-SiMe3 remained unreacted. Condensation of the residue at 200 °C in vacuo proved all Si-containing species to be distillable; 31P-NMR showed that upon cleavage reaction n-Bu4PCI was in part reacted to give n-Bu3P and traces of n-Bu2PH; unreacted n-Bu4PCI remained in the reaction residue. Example 3:
Substrate 1 as defined in Table 1 above (260 mg) and the catalyst mixture (n-Bu4PCI, 2-MIA; 7 w% each) were reacted in a sealed NMR tube at 160° C for 25 hours. In a second reaction the mixture was directly heated to 220 °C. The results are listed in Table 8.
Table 8
Figure imgf000044_0001
Example 4:
Tri- and tetrasilanes as displayed in Table 9 were synthesized from disilane 1 (4.3 g) and 1 MIA (0.5 g) in a 100 ml flask at 165 °C for 3 h.
Table 9
Figure imgf000044_0002
A mixture of oligosilanes (380 mg) listed in Table 9 was then reacted with the catalyst mixture comparably to the previous Examples (n-Bu4PCI, 2-MIA; 5 w% each) in a sealed NMR tube at different temperatures. The results are shown in Table 10. Table 10
Figure imgf000045_0001
(* Reference)
Heating the mixture of oligosilanes to 160 °C for 7 h more tri- and tetrasilanes were formed and no significant cleavage reactions of the oligosilanes were detected. Cleavage of the oligosilanes started at 220 °C/8 h with formation of hydrido silanes and decomposition of n-Bu4PCI to n-Bu3P.
Example 5:
Disilane 1 (523 mg) was admixed with 5 w% of 2-MIA in a sealed NMR tube. Heating of the sample to 140 °C for 23 h showed no significant reaction, after 48 h monomer 8 starts to form, and a lower amount of trisilane 26 and tetrasilane 27 were formed as well in a ratio of 1 :0.8:0.2. After 68 h reaction time, 26mol% of monosilanes were formed (8, 25mol%; 7, 1 mol%), 28mol% of disilane 1 remained unreacted, trisilane 26 was formed in 30mol%, and the tetrasilane 27 in 16mol%. Additional heating to 220 °C for 21 h lead to significant hydridosilane formation (5, 36mol%; 6, 2mol%). After an overall reaction time of 68 h at 140 °C and 80 h at 220 °C nearly all di- and oligosilanes were decomposed, the products are listed in Table 1 1 . Prolonged reaction times did not change product composition; that may be due to complete decomposition of 2-MIA, because this compound could not been recycled from the reaction mixture. We conclude that 2-MIA was the source for hydrogenation of chlorosilanes obtained from di- and oligosilane splitting at high reaction temperatures. Table 11
Figure imgf000046_0001
(* Reference) Example 6:
Disilane 1 (492 mg) was reacted with n-Bu4PCI (5 w%) at different temperatures and reaction times in a sealed NMR tube. Products formed are listed in Table 12. As demonstrated by Examples 8 and 9, both catalysts react similar at high temperatures. 2-MIA produced oligosilanes faster compared to n-Bu4PCI that subsequently were cleaved, while the phosphonium chloride formed oligosilanes that nearly simultaneously were reacted to monosilanes.
Table 12
Figure imgf000046_0002
(* Reference)
From 31P-NMR spectroscopic investigations on the reaction mixture it is concluded that at low temperatures (23 h/140 °C) n-Bu4PCI remained unreacted and acts as a catalyst. At higher temperatures (160 °C/25 h) n-Bu3P was starting to form besides an unidentified P-containing compound (31P-NMR: +23 ppm) that became dominant in the reaction mixture. At prolonged heating (160 °C/75 h to 220 °C/10 h) the n-Bu3P content was increasing but interestingly n-Bu4PCI was recycled under these conditions, the non-identified compound detected at +23 ppm was completely decomposed. Two new signals at -23 and one at -98 ppm demonstrate complex interactions of n-Bu PCI with the reaction mixture that finally lead to disilane splitting and hydrogen transfer to give hydrido monosilanes.
Example 7:
Disilane 1 (426 mg) was reacted separately with 5 w% of each catalyst (n-Bu PCI; 2-MIA) in a sealed NMR tube at 220 °C for 21 h, resulting in formation of the product mixtures listed in Table 13. It was shown that under these reaction conditions, hydridosilane formation was favoured with 2-MIA.
Table 13
Figure imgf000047_0001
15mol% of 1 and oligosilanes remained unreacted in case of n-Bu PCI vs. 10mol% in case of 2-MIA. n-Bu PCI was nearly completely reacted to give n-Bu3P besides three compounds detected at -23.17, 23.19 and -95.74 ppm. Also 2-MIA was completely decomposed to give a yellow highly viscous liquid. At temperatures < 140 °C 2-MIA acts as disproportionation catalyst, at T> 160 °C it is a reaction partner to form hydridosilanes. Under the same conditions n-Bu PCI decomposed to give n-Bu3P and 1-but-ene. The hydrogen chloride formed during decomposition of the catalyst acts as cleavage and Si-H forming agent. While the 1-but-ene was identified NMR spectroscopically, no formation of butyl chloride and HCI could be detected. Example 8
Disilane 1 (302 mg) was reacted with a mixture of n-Bu3P (30 mg) and butyl chloride (14 mg) in a sealed NMR tube at 220 °C for 70 h. Reaction products identified were monosilanes 8 (Me2SiCI2 35mol%), 5 (Me2SiHCI 30mol%), 7 (Me3SiCI 13mol%), 9 (Me3SiH 2mol%) and 6 (Me2SiH2 2mol%). Besides these products, carbodisilane 21 was formed in 18mol%; other carbodisilanes with higher degree of chlorination were detected in traces.
Treating of disilane 1 with solely butyl chloride (without phosphane) under comparable conditions gave no hint to any reaction.
Example 9
20 w% of n-Bu4PCI were admixed with disilane 1 (352 mg) and reacted in a sealed NMR tube at different temperatures. Products obtained are listed in Table 14.
Table 14
Figure imgf000048_0001
(* Reference)
At 140 °C (64 h) monosilanes were already obtained but only 6mol% of hydridosilane 5, oligosilanes were still present in the mixture (5mol%). Subsequent heating of the sample to 220 °C (24 h) increased the amount of silane 5 to 30mol%. Hydridosilanes 9 and 6 were formed in 5 and 3mol%. Direct heating of 1 (402 mg) with 21 w% of n-Bu4PCI even accelerated conversion and increased Si-H formation in comparison of low temperature reaction (140°C); only traces of disilane or oligosilanes remained unreacted. Example 10
A mixture of 1 (302 mg) and 2-MIA (14 w%) was heated to 140 °C for 64 h. Monosilane 8 was obtained in 62mol%, 7 in 22mol%, Si-H formation was not detected. Subsequent heating of the sample to 220 °C (64 h) gave silanes 5 in 37mol%, 8 in 40mol%, 7 in 13mol% and 6 in 10mol%. No disilane and oligosilanes remained unreacted; disilane conversion into monosilanes was quantitative. Direct heating of 1 (302 mg) to 220 °C (64 h) with 15 w% 2- MIA even accelerated both conversion and Si-H formation, no di- and oligosilanes remained in the reaction mixture. Example 11 (starting material)
6 g of a mixture consisting of disilanes 14 (71 mol%), 15 (24mol%), 1 (3mol%) and 16 (1 mol%), was reacted with 1-methylimidazole (1 g) at 165 °C for 3 hours to give a mixture of oligosilanes listed in Table 15.
Table 15
Figure imgf000049_0001
Example 12
The disilane mixture listed in Example 1 1 (470 mg) as well as the mixture of oligosilanes (566 mg, Table 15) were reacted with both catalysts (2-MIA and n-Bu4PCI, 5 w% each) in a sealed NMR tube at 220 °C for 17 h. Products obtained are listed in Table 16. It is demonstrated that product formation in both cases is comparable. Cleavage reactions were quantitatively, no di- or oligosilanes remained unreacted. Table 16
Figure imgf000050_0001
Notably, the oligosilanes produced a significantly higher amount of hydrido silanes (17, 53mol%; 6, 6mol% vs. 17, 21 mol%, no 6) while the amount of chlorosilane 8 was significantly higher for the disilane mixture. (31 mol% vs. 9mol%). In both samples, n-Bu4PCI was completely converted to give n-Bu3P.
Example 13
A mixture of disilanes (490 mg) (Table 6) was reacted with the catalysts (n-Bu4PCI and 2- MIA, 5 w% each) in a sealed NMR tube at 220 °C for 8h. The results are displayed in Table 17.
Table 17
Figure imgf000050_0002
Example 14A
Reaction of a mixture (1.06 g) of disilanes 1 (95mol%) and 2 (5mol%) with n-Bu4PCI (14 w%) in the presence of HCI in a sealed glass ampoule at 220 °C for 91 h gave monosilanes and unreacted disilane 1 as listed in Table 18A; but-1-ene was detected by 1H-NMR spectroscopy. Table 18A
Figure imgf000051_0003
Example 14B:
CIMe2Si-SiMe2CI (4.44 g, 1 eq) was reacted with 2-methylimidazole (1.0 g, 0.5 eq) at 220 in a sealed glass ampoule for 67 h. 3.54 g monosilanes were isolated after separation condensation in vacuo, composition is listed in Table 18B.
Table 18B
Figure imgf000051_0004
Additionally, compound
Figure imgf000051_0001
and were identified by NMR spectroscopy that was formed from the starting reactants with release of HCI at lower reaction temperatures.
From the high temperature experiment
Figure imgf000051_0002
was isolated in the residue after condensation and was characterized by X-ray diffraction, spectroscopic and microanalytical methods. Synthesis and cleavage reactions of mixed methylchloro/methylhydrido disilanes
For hydrogenation of methylchlorodisilanes tributyltin hydride was used as reducing agent. For the preparation of n-Bu3SnH see: U. Herzog, G. Roewer and U. Patzold, Katalytische Hydrierung chlorhaltiger Disilane mit Tributylstannan, J. Organomet. Chem 1995,494, 143- 147.
Example 15
Disilane 1 (CIMe2Si-SiMe2CI, admixed with 5mol% Me3Si-SiMe2CI 2) (4.04 g) was reacted in a 1/1 molar ratio with the tin hydride in diglyme and tetraphenylphosphoniumchlonde (Ph4PCI, 3 w%) as catalyst at r.t.. After work up, a mixture of the disilanes 1 (15mol%), 2 (4mol%), 3 (72mol%) and 4 (9mol%) was obtained. 200 mg of those disilanes were subsequently reacted with tetrabutylphosphoniumchloride (n-Bu4PCI, 25 w%) in a sealed NMR tube at 180°C for 9 h. As listed in Table 19, the hydrido disilane 3 was nearly completely cleaved into the monosilanes 5 and 6 that were formed in 68mol% yield. Chlorosilane 7 results from cleavage of the disilane 2. Unidentified oligosilanes were detected in small amounts.
Table 19
Figure imgf000052_0001
Example 16
The mixture of disilanes 1-4 from Example 15 (200 mg) was reacted with 2-methylimidazole (2-MIA, 16 w%) in a sealed NMR tube at 220 °C for 9 h. The amount of chlorosilane 5 was significantly smaller than in Example 15, the main product obtained was dimethylsilane Me2SiH2 6, followed by Me3SiCI (7, 13.2mol%). Remaining disilanes 2 and 4 were 15.0mol% resp. 8.2mol%. Notably, perhydrogenated disilane 10 was detected in 1.0mol% (Table 20). Prolonged reaction times (69 h) lead to almost quantitative splitting of H-substituted disilanes as well as conversion of tri- and tetrasilanes (26 and 27), named in the table as "oligosilanes", into monomers. Products obtained are listed in Table 21 and prove formation of Me2SiHCI (~40mol%) as main component. Table 20
Figure imgf000053_0001
Example 17
80 mg of a mixture containing methylhydndodisilanes 11 (85mol%) and 12 (15mol%) were reacted with (n-Bu4PCI, 18 w%) in a sealed NMR tube. Cleavage reaction started already at r.t. and was completed at 50 °C for 62 h. Monosilanes formed were MeSiH3 (13, 75mol%), Me2SiH2 (6, 18mol%) and Me2SiHCI (5, 7mol%). The catalyst remained nearly unreacted and only traces of n-Bu3P were detected in the 31 P-NMR spectrum.
With 2-MIA (10 w%) as catalyst monosilane formation started at 180 °C (16 h) and was finished at 220 °C for 90 h to give 13 (82mol%) and 6 (18mol%) quantitatively.
Example 18
Tetramethyldisilane (80 mg, 10) was reacted with n-Bu4PCI (54 w%) in a sealed NMR tube and completely cleaved at 180 °C (17 h) to give Me2SiH2 (6, 87mol%) Me3SiH (9, 7mol%), Me2SiHCI (5, 4mol%) and Me3SiCI (7, 2mol%).
Example 19A (starting material)
A mixture (1 .22 g) of methylchlorodisilanes 14 (72mol%), 15 (23mol%), 1 (3.5mol%) and 16 (1 .5mol%) was reacted in a 50 ml flask with n-Bu3SnH in different molar ratios. In sample I about 18mol% of the chloro substituents were replaced by H-substituents, in sample II 37mol% and in sample III 55mol%. The reductions were performed in diglyme (1 ml) with PPh4CI (4 w%) as catalyst for 64h at r.t to give the disilane mixtures I to III (Table 22-24).
Table 22
Figure imgf000054_0001
Example 19B
Sample I (Table 22) (150 mg) was reacted with n-Bu4PCI (17 w%) in a sealed NMR tube at different temperatures. Product compositions and molar distributions were determined NMR- spectroscopically. The results are listed in Table 25.
Table 25
Figure imgf000055_0001
Sample II (Table 23) (150 mg) was reacted with n-Bu4PCI (19 w%) in a sealed NMR tube at different temperatures. Product compositions and molar distributions were determined NMR- spectroscopically. The results are listed in Table 26.
Table 26
Figure imgf000055_0002
As concluded from Table 26 disilane cleavage already started at r.t. H-substituted disilanes were already completely cleaved to mainly give the chlorosilanes 17 (61.2mol%), 18 (5.5mol%) and 8 (14.6mol%). Chlorinated methylsilanes require significantly higher temperatures for cleavage. MeSihh (13, 2mol%) is only formed at 220 °C, possibly by H-CI exchange of monomeric species.
Disilanes of sample II were mostly cleaved at r.t. to monomers, only 1 remained unreacted. At 220 °C (23 h) this disilane too was completely converted to monosilanes.
Sample III (Table 24) (200 mg) was nearly completely reacted with n-Bu4PCI (24 w%) already at 80 °C within 15 min to give the monosilanes as listed in Table 27, only traces of 1 remained uncleaved.
Table 27
Figure imgf000056_0001
Summarizing the experiments of Example 19B, cleavage reactions with n-Bu4PCI proved that cleavage of disilanes was faster with increasing degree of hydrogenation at the silicon backbone. The cleavage is decelerated with increasing degree of methylation at silicon. In case of silicon chlorination cleavage is accelerated with increasing degree of chlorination at the silicon moiety.
Example 20A (Starting Material)
For simulation of a mono- and disilane fraction obtained from the Muller-Rochow-Direct Process, a mixture (1.10 g) of compounds listed in Table 4, (1.19 g) of monosilane 8 and highly chlorinated disilanes listed in Table 5 and (1.07 g) of compounds listed in Table 7 were mixed and reacted with different molar amounts of n-Bu3SnH (procedure is described in Example 33) to replace 25, 50 and 75mol% of all chlorine substituents at silicon. After reduction, the products were isolated by condensation/distillation to give the product mixtures IV, V and VI listed in Table 28.
Table 28
Figure imgf000057_0001
Example 20B
Cleavage reactions with mixture IV (280 mg) were performed with n-Bu4PCI (6 w%) in a sealed NMR tube. NMR measurements were taken at r.t. , 140 °C (23 h) and 220 °C (16 h). Cleavage reactions already started at r.t. and only traces of Me3Si-SiMe3 (~1 mol%) remained unreacted at 220 °C (Table 29). Table 29
Figure imgf000058_0001
In Table 30 the results of the comparable cleavage reactions of samples V and VI are listed.
Table 30
Figure imgf000058_0002
From cleavage reactions of samples IV - VI it is obvious that with increasing replacement of CI against H in the methylchlorodisilanes RnSi2Cl6-n with Cl>3, the partial hydrido substituted disilanes were cleaved significantly faster. Cleavage of disilanes with Me>4 (partial or perhydrogenated) required higher temperatures. At about 140 °C mainly the chlorosilanes 8, 7, 5 and 17 were formed. Investigation of the cleavage reactions by 31P-NMR spectroscopy proved the activity of n-Bu4PCI as real catalyst, only at 220 °C and higher, the latter is completely reacted to give n-Bi P, traces of n-Bu2PH and 1-but-ene, and hydrogen chloride. HCI is responsible for the final formation of H/CI substituted monosilanes.
Example 21
In a 50 ml flask, a mixture of disilanes 14 (69mol%), 15 (26mol%), 1 (4mol%) and 16 (1 mol%) (244 mg) was reacted with Ph4PCI (25.3 mg) and LiH (202 mg) in 0.5 mL of diglyme. Already at r.t. 75mol% of monosilanes were formed, with 17 in 40mol%. 25mol% of disilanes remained uncleaved, 10mol% of those were reduced (SiCI - SiH) (Table 31). MeSih that might have been formed evaporated in the open system due to its low boiling point (-57 °C). That is why the same disilane mixture (122 mg) was reacted with the catalyst/LiH (1 w%/4 w%) in a sealed NMR tube at r.t.. In this case monosilane 13 was detected in 13mol%, 17 was formed in 21 mol% and 18 in 33mol% yield.
Table 31
Figure imgf000059_0001
Example 22
A mixture of disilanes 1 (62mol%), 2 (30mol%), 15 (4mol%), and 14 (4mol%) (107 mg) was reacted with the n-Bu4PCI/LiH system (1.3 mg/29.3 mg) and 0.3 ml diglyme as solvent in a sealed NMR tube first at r.t. and then at 200 °C for 23 h. As can be seen from Table 32, under low temperature conditions the disilanes were initially reduced, perhydrogenated disilanes 10 and 4 were formed in 82.6mol% and 17.5mol%; traces of hydrogenated monosilanes Me2SiH2 and MeSiH3 were also detected. At 200 °C all disilanes were completely cleaved.
The 31P-NMR spectrum of the sample proved that n-Bu4PCI was completely reacted to give n-Bu3P and traces of n-Bu2PH. Reinvestigations showed that nearly all disilanes were already cleaved at 140 °C.
Table 32
Figure imgf000060_0001
Example 23
The mixture of mono- and disilanes from Example 2 (Table 5) (167 mg) was reacted with 73 mol% LiH (15 mg) and n-Bu4PCI (2.9 mg) and 0.3 ml diglyme as solvent in a sealed NMR tube at first at r.t. and subsequently at 140 °C (23 h). The product distribution is listed in Table 33. At 140 °C the amount of dichlorosilane 8 increased significantly from 15mol% to 37mol%, obviously from cleavage of disilane 1 that was still present at r.t.. At 140 °C the amount of 13 is strongly decreased (26mol% - 9mol%), while that of 17 was strongly increased (6mol% - 16mol%). Notably, the catalyst remained unchanged under those conditions (no n-Bu3P formation).
Table 33
r.t. 140 °C
compound mol% mol%
MeSiHCI2 6 16
Me2SiHCI 20 10
MeSiH2CI 26 23
Me2SiH2 2 -
MeSiHs 26 9
Me2SiCI2 15 37
MesSiCI 3 3
CIMe2Si-SiMe2CI 1 -
Me3Si-SiMe2CI 1 2
Me6Si2 traces traces Example 24
The mixture of mono- and disilanes of Example 2 (Table 6) (97 mg) was reacted with 100 mol% LiH (10 mg) and n-Bu4PCI (3.2 mg) and 0.3 ml diglyme as solvent in a sealed NMR tube, first at r.t. and subsequently at 140 °C (23 h). Product distribution is listed in Table 34. In the presence of the catalyst, even the partially- and perhydrogenated methyldisilanes were mostly cleaved at r.t., the perchlorinated methyldisilanes remained unreacted. At 140 °C monosilanes 6, 13, and 5 became main products (94mol%), only 3mol% of disilanes 2 and 26 were still detected in the reaction mixture. Upon cleavage reaction, the catalyst was not reacted to give n-Bu3P.
Table 34
Figure imgf000061_0001
Example 25
The mixture of mono-, di- and carbodisilanes from Example 2 (Table 4) (143 mg) was reacted with 100 mol% LiH (15.4) and the catalyst n-Bu4PCI (4.1 mg) and 0.3 ml diglyme as solvent in a sealed NMR tube at r.t. and subsequently at 140 °C (23 h). Product formation is shown in Table 35. Cleavage reactions already started at r.t., 85mol% of monomers were obtained in presence of the catalyst. Increasing the reaction temperature to 140 °C, the amount of Me2SiH2 (6, 39mol%) was increased significantly by cleavage of mainly disilanes 10, 3, 4, 1 , and 2. Notably, even the carbodisilanes were reacted to monosilanes, as documented by the high amount of methylsilane (13, 59mol%). At r.t., the catalyst remained unchanged but was decomposed at 140°C to give an unknown species besides n-Bu3P. Table 35
Figure imgf000062_0001
Example 26
In a 100 ml flask, the mixture of mono- and disilanes (10.6 g) from Example 2 (listed in Table 6) was reacted with n-Bu4PCI (0.28 g) and LiH (0.8 g, 75 mol%) in 5 mL of diglyme at 130 °C for 5 h. Volatile products formed (3.22 g) were separated by condensation and are listed in Table 36. NMR spectroscopic investigations of the residue proved formation of highly methylated hydrogen substituted disilanes and carbodisilanes but they remained mostly uncleaved. Instead, increasing the reaction temperature to 160 °C (5 h) and characterization of low boiling components (1.03 g) proves significant cleavage of all disilanes and even the carbosilanes to mainly produce the technically very valuable monosilanes MeSiHC (40mol%) and MeSiH2CI (26mol%) (Table 36). In the reaction residue traces of highly methylated disilanes besides small amounts of uncleaved carbodisilanes were identified.
Table 36
Figure imgf000062_0002
Example 27
In a 100 ml flask, the mixture of mono- and disilanes from Example 2 as listed in Table 4 was reacted with n-Bu4PCI (0.36 g) and LiH (0.53 g, 51 mol%) in 6 mL of diglyme at 130 °C for 5 h. Volatile products (1.66 g) formed were separated by condensation and are listed in Table 37. Highly methylated hydrogen substituted disilanes and carbodisilanes were formed but remained mostly uncleaved. Reaction at 160 °C for 5 h and condensation of the volatile products formed (0.98 g) were identified as monosilanes, also listed in Table 37. In the reaction residue traces of highly methylated disilanes besides small amounts of uncleaved carbodisilanes were detected.
Table 37
Figure imgf000063_0001
Example 28
The mixture of mono- and disilanes (357 mg) of Example 2 (listed in Table 5) was reacted with n-Bu3P (16 mg) in a diglyme/HCI solution (1 1.6 M) (molar ratio disilane/HCI 1 :1) in a sealed NMR tube at 80°C for 16.5 h to give monomers in 97.1 mol% (listed in Table 38). Only highly methylated disilanes 1 and 2 were still present. No oligomeric structures could be detected NMR spectroscopically. For this reaction no other hydrogen source was required except HCI that presumably reacted as a silylene trapping agent preventing the silylene insertion into the Si-Si-bond giving oligomeric structures. The main products formed were MeSiC (39.7mol%), Me2SiCI2 (28.1 mol%) and MeSiHC (27.6mol%). Table 38
Figure imgf000064_0001
It will be understood that any numerical range recited herein includes all sub-ranges within that range and any combination of the various endpoints of such ranges or sub-ranges, be it described in the examples or anywhere else in the specification.
It will also be understood herein that any of the components of the invention herein as they are described by any specific genus or species detailed in the examples section of the specification, can be used in one embodiment to define an alternative respective definition of any endpoint of a range elsewhere described in the specification with regard to that component, and can thus, in one non-limiting embodiment, be used to supplant such a range endpoint, elsewhere described.
It will be further understood that any compound, material or substance which is expressly or implicitly disclosed in the specification and/or recited in a claim as belonging to a group of structurally, compositionally and/or functionally related compounds, materials or substances includes individual representatives of the group and all combinations thereof.

Claims

1 . Process for the manufacture of monosilanes of the general formula (I): MexSiHyClz (I), wherein
x = O to 3,
y = 0 to 3, preferably 1 to 3, more preferably 1 or 2,
z = O to 4 and
x + y + z = 4,
and mixtures thereof,
comprising:
A) the step of subjecting a silane substrate comprising one or more silane substrate compounds selected from the group of a) one or more disilanes of the general formula (II)
MemSi2HnClo (II)
wherein
m = 0 to 6,
n = 0 to 6, preferably 0 to 4,
o = 0 to 6 and
m + n + o = 6, b) one or more linear or branched oligosilanes of the general formula (III)
MepSiqHrCIs (II I),
wherein
q = 3 to 7
p = q to (2q + 2)
r, s = 0 to (q + 2)
r + s = (2q + 2) - p
and wherein each Si atom preferably bears at least one methyl group, and c) one or more carbodisilanes of the general formula (IV) (MeaSiHbCle)-CH2-(MecSiHdClf) (IV)
wherein
a, c are independently of each other 1 to 3,
b, d are independently from each other 0 to 2
e, f are independently from each other 0 to 2,
a + b + e = 3,
c + d + f = 3,
and mixtures containing compounds of the general formulae (II), (III) and (IV), to the cleavage reaction of the silicon-silicon bond(s) in the silane substrates of the general formulae (II) and (III) and the silicon-carbon bond(s) of the carbodisilanes of the general formula (IV),
to the reaction with at least one compound (cleavage compound) selected from the group consisting of:
- a quaternary Group 15 onium compound R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I ,
- a heterocyclic amine,
- a heterocyclic ammonium halide,
- a mixture of R3P and RX, wherein R is as defined above, and X is as defined above, and
mixtures of the above-mentioned compounds,
(i) until at least about 50 mol-% of the cleavage compound based on the initial molar amount of the cleavage compound is reacted, and/or
(ii) until the ratio of the total of the produced monosilanes of the general formula (I) wherein y = 1 to 3 is at least about 40 mol-%, preferably at least about 50 mol-%, based on the total molar amount of the monosilanes of the general formula (I), and/or
(iii) until the ratio of Me2SiHCI is at least about 20 mol-%, preferably at least about 30 mol-%, based on the total amount of the monosilanes of the general formula (I), and optionally a step of separating the resulting monosilanes of the general formula (I). Process according to claim 1 , wherein the reaction in step A) is carried out for more than about 4 hours and at a temperature of at least about 200 °C, or the reaction in step A) is carried out for more than about 10 hours preferably, at a temperature of more than about 100 °C. Process according to claims 1 or 2, which is carried out without the supply of hydrogen (H2).
Process according to any of the previous claims, wherein the quaternary Group 15 onium compound is represented by the formula R4PCI, wherein R is independently a hydrogen group or an organyl group, more preferably a hydrogen group, an aromatic group or an aliphatic hydrocarbon group, optionally step A) is carried out in the presence of at least one compound of the formula R4PCI, preferably n-Bu4PCI, and optionally at least one methylimidazole.
Process according to any of the previous claims, wherein step A) is carried out by subjecting the silane substrate to the cleavage reaction of step A) in the presence of a hydrogen halide HX, wherein X is selected from the group consisting of F, CI, Br and I.
Process according to any of the previous claims, wherein step A) is carried out in the presence of at least one metal hydride, preferably at least one metal hydride selected from the group of alkali metal hydrides and alkaline earth metal hydrides, more preferably at least one alkali metal hydride, and most preferably lithium hydride.
Process according to any of the previous claims, wherein the silane substrate, comprises at least one of the compounds selected from the group consisting of Si2CI6, C MeSi-SiMeCIH, HCIMeSi-SiMeCIH, CI2MeSi-SiMeH2, HCIMeSi-SiMeH2, CIMe2Si-SiMeCIH, CI2MeSi-SiMe2H, CIMe2Si-SiMeH2, HMe2Si-SiMeCIH, CIMe2Si- SiMe2CI, Me3Si-SiMe2CI, CIMe2Si-SiMe2H, Me3Si-SiMe2H, HMe2Si-SiMe2H, H2MeSi- SiMeH2, HMe2Si-SiMeH2, CI2MeSi-SiMeCI2, CIMe2Si-SiMeCI2, Me3Si-SiMeCI2, CI2MeSi-CH2-SiMeCI2, CIMe2Si-CH2-SiMeCI2, CIMe2Si-CH2-SiMe2CI, Me3Si-CH2- SiMeC , Me3Si-CH2-SiMe2CI, Me3Si-CH2-SiMe3, CIMe2Si-SiMe2-SiMe2CI, CIMe2Si- SiMe2-SiMe2-SiMe2CI, (CIMe2Si)3SiMe, CIMe2Si-SiMe2-SiMe2H, (CI2MeSi)2SiMeCI, (CI2MeSi)3SiMe, (CI2MeSi)2SiMe-SiCIMe-SiCI2Me, [(CI2MeSi)2SiMe]2,
[(CI2MeSi)2SiMe]2SiCIMe, and (CI2MeSi)2SiMe-SiMe2CI, and mixtures thereof.
Process according to any of the previous claims, wherein the molar ratio of the cleavage compound used in step A) to the silane substrate compounds of the general formulae (II), (III) and (IV) is in the range of about 0.0001 to about 100 mol-%, more preferred 0.001 to 50 mol-%, more preferred 0.001 to 25 mol-%, even more preferred 0.01 to 10 mol-%, and most preferably 0.01 to 0.5 mol-% based on the molar amount of the silane substrate compounds.
Process according to any of the previous claims, wherein the silane substrates used in step A) are submitted to a hydrogenation step before the cleavage reaction of the silicon-silicon bond(s) in the silane substrates of the general formulae (II) and (III) and/or the silicon-carbon bond(s) of the carbodisilanes of the general formula (IV) is carried out, wherein chlorine atoms contained in the silane substrates are partially or completely exchanged by hydrogen atoms, and preferably the hydride donor selected from the group of metal hydrides, preferably complex metal hydrides and organometallic hydride reagents such as LiAIH4, n-Bu3SnH, NaBH4, /'-BU2AIH or sodium bis(2-methoxyethoxy) aluminumhydride.
Process according to any of the previous claims, wherein step A) is carried out in the presence of an organic solvent, preferably a high-boiling ether compound, more preferably diglyme or tetraglyme, most preferably diglyme.
Process according to the previous claims, wherein step A) is carried out in the presence of at least one compound of the formula R4PCI, preferably n-Bu4PCI, and at least one metal hydride, preferably lithium hydride.
Process according to any of the previous claims, wherein step A) is carried out using at least one cleavage compound selected from quaternary Group 15 onium compounds represented by the formula R4QX, wherein each R is independently a hydrogen or an organyl group, Q is phosphorus, arsenic, antimony or bismuth, and X is a halide selected from the group consisting of F, CI, Br and I, and at least one cleavage compound selected from heterocyclic amines and heterocyclic ammonium halides, at a temperature of about 0 °C to about 300 °C, more preferably about 50 °C to about 220 °C, even more preferably at about 100 to about 200 °C, and most preferably at about 120 °C to about 180 °C.
Process according to any of the previous claims, wherein the monosilanes of the formula (I) are selected from the group consisting of Me2SiHCI, Me2SiH2, Me3SiCI, Me2SiCI2, Me3SiH, MeSih , MeSiHC , MeSiH2CI, and MeSiC , preferably the monosilanes of the formula (I) are selected from the group consisting of Me2SiHCI, Me3SiCI, and MeSiHC .
Process according to any of the previous claims, wherein dimethylchloromonosilane Me2SiHCI is formed by submitting a silane substrate selected from the group consisting of CIMe2Si-SiMe2CI, CIMe2Si-SiMeCI2, Me3Si-SiMe2CI, HMe2Si-SiMe2H, HMe2Si-SiMeH2, Me3Si-SiMe2H, CIMe2Si-SiMe2H, CIMe2Si-SiMeH2, HMe2Si-SiMeCI2, CI2MeSi-CH2-SiMeCI2, CIMe2Si-CH2-SiMeCI2, CIMe2Si-CH2-SiMe2CI, Me3Si-CH2- SiMe2CI, CIMe2Si-SiMe2-SiMe2CI, CIMe2Si-SiMe2-SiMe2-SiMe2CI, (CIMe2Si)3SiMe and mixtures thereof to the cleavage reactions of step A), and/or
wherein the trimethylchlorosilane Me3SiCI is formed by submitting a silane substrate selected from the group consisting of Me3Si-SiMe2CI, Me3Si-SiMeCI2, Me3Si-SiMe2H, Me3Si-CH2-SiMe2CI, CIMe2Si-CH2-SiMe2CI, CIMe2Si-CH2-SiMeCI2, Me3Si-CH2-SiMe3, Me3Si-CH2-SiMeCI2 and mixtures thereof to the cleavage reactions of step A), and/or wherein the methyldichloromonosilane MeSiHCI2 is formed by submitting a silane substrate selected from the group consisting of CI2MeSi-SiMeCI2, CI2MeSi-SiMe2CI, CI2MeSi-SiMe3, HCIMeSi-SiMeH2, HCIMeSi-SiMeCIH, HCIMeSi-SiMeCI2, CI2MeSi- SiMeH2, CIHMeSi-SiMe2CI, CI2MeSi-SiMe2H, CIHMeSi-SiMe2H, CI2MeSi-CH2- SiMeC , CIMe2Si-CH2-SiMeCI2, Me3Si-CH2-SiMeCI2, (CI2MeSi)2SiMeCI, (CI2MeSi)3SiMe, (CI2MeSi)2SiMe-SiCIMe-SiCI2Me, [(CI2MeSi)2SiMe]2,
[(CI2MeSi)2SiMe]2SiCIMe, (CI2MeSi)2SiMe-SiMe2CI and mixtures thereof to the cleavage reactions of step A).
Process according to any of the previous claims, wherein the silane substrates of the general formulae (II) and (III), and the carbodisilane substrates of the general formula (IV), or the mixtures thereof are residues of the Rochow-Muller Direct Process (DPR).
PCT/US2018/051853 2017-09-20 2018-09-20 Disilane-, carbodisilane-and oligosilane cleavage with cleavage compound acting as catalyst and hydrogenation source WO2019060481A1 (en)

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