JP7580983B2 - Method for producing cyclic hydrogenated polysilane compound - Google Patents

Description

The present invention relates to a method for producing a hydrogenated polysilane compound using a reducing agent.

Silicon films are used in solar cells, semiconductors, etc., and these silicon films have traditionally been produced by chemical vapor deposition (CVD) using monosilane as a raw material. Other methods for producing silicon films that have been reported include CVD using hydrogenated polysilane compounds as raw materials, and a method in which a solution layer containing hydrogenated polysilane compounds as a solute is formed on a substrate and hydrogenated polysilane compounds are produced by photopolymerization.

It is known that hydrogenated polysilane compounds can be prepared, for example, by reacting a perphenylcyclosilane mixture with a Lewis acid compound, bubbling hydrogen chloride gas into the resulting dispersion, and then reacting the product with lithium aluminum hydride, which is a reducing agent (Patent Document 1).

U.S. Pat. No. 7,498,015

In the technology of Patent Document 1, lithium salts and aluminum salts and/or complexes thereof derived from Lewis acid compounds and/or lithium aluminum hydride are formed as solid residues, which may result in the solid residues adhering to the walls of the tank, piping, etc. in the reaction system, making cleaning of the solid residues cumbersome. There is also the problem that the solid residues are not easy to handle or process after the target product is extracted. There is also the possibility of danger, such as the clogging of piping or filters by the solid residues or the stoppage of agitation due to the solid residues adhering to the agitator.

As described above, when producing hydrogenated polysilane compounds by reduction reaction, the disposal of solid residues becomes complicated, and it is necessary to supply hydrogenated polysilane compounds more safely and stably. The present invention has been made in consideration of the above circumstances, and its object is to provide a method for producing hydrogenated polysilane compounds that can stably and efficiently produce hydrogenated polysilane compounds without generating almost any solid residues even when subjected to reduction reaction.

The gist of the present invention, which has solved the above problems, is as follows.
The method for producing a hydrogenated polysilane compound of the present invention is a method for producing a hydrogenated polysilane compound (D) from a composition containing a polyhalosilane compound (A) containing a Si-Si bond and a Si-X bond (X represents a halogen atom) in the molecule, a reducing agent (B), and a solvent (C), in a batch reactor, characterized in that the reducing agent (B) and/or a reaction product of the reducing agent (B) is liquid at a temperature of 30° C., and the method comprises: (i) a step of removing the reducing agent (B) and/or the reaction product of the reducing agent (B) by mixing with an acidic aqueous solution after at least contacting the polyhalosilane compound (A) with the reducing agent (B), and/or (ii) a step of extracting the hydrogenated polysilane compound (D) by distillation.

In the present invention, the reducing agent (B) is either aluminum hydride or boron hydride, and the reducing agent (B) is preferably an aluminum hydride having Al-R ¹ (R ¹ is an alkyl group which may be branched) or Al-OR ² (R ² is an alkyl group which may be branched).
The hydrogenated polysilane compound (D) preferably contains cyclopentasilane or cyclohexasilane.
In the present invention, the solvent (C) may contain a hydrocarbon solvent.

According to the present invention, hydrogenated polysilane compounds can be produced stably and efficiently without generating any solid residue even when subjected to a reduction reaction.

The method for producing a hydrogenated polysilane compound of the present invention is a method for producing a hydrogenated polysilane compound (D) from a composition containing a polyhalosilane compound (A) containing an Si-Si bond and an Si-X bond (X represents a halogen atom) in the molecule, a reducing agent (B), and a solvent (C) in a batch reactor, in which the reducing agent (B) and/or the reactant of the reducing agent (B) are liquid at a temperature of 30°C, and after at least contacting the polyhalosilane compound (A) with the reducing agent (B), the method includes (i) a step of removing the reducing agent (B) and/or the reactant of the reducing agent (B) by mixing with an acidic aqueous solution, and/or (ii) a step of extracting the hydrogenated polysilane compound (D) by distillation.

In the present invention, when the reducing agent (B) and/or the reactant of the reducing agent (B) is liquid, it becomes possible to safely and stably prepare a hydrogenated polysilane compound by contacting it with an acidic aqueous solution and by isolating the hydrogenated polysilane compound by distillation, with almost no solid residue being produced.
In the present invention, the reactant of the reducing agent includes an aluminum-containing compound (for example, an aluminum salt or a complex thereof).

The reaction site for producing hydrogenated polysilane compounds is a batch reactor in which the compounds are sequentially fed, reacted, and removed.

The batch reactor is not particularly limited as long as it can prepare a hydrogenated polysilane compound, but may be made of, for example, a metal or glass, preferably glass, stainless steel, titanium, copper, nickel, aluminum, or an alloy thereof.

The batch reactor may have a vessel structure, such as a kettle, flask, beaker, etc., so that supply, reaction, removal, etc. can be performed in sequence. The cross section of the vessel structure may be an ellipse, circle, semicircle, triangle, square, or other polygon, or a combination of these.

The amounts of polyhalosilane compound and reducing agent added may be adjusted as appropriate so that these compounds react stoichiometrically, and the amount (concentration) of polyhalosilane compound used, the amount (concentration) of reducing agent used, the solvent that may be used for the polyhalosilane compound and the amount used thereof, and the temperature of the batch reactor may be as described below.

The following describes the polyhalosilane compound (A) containing Si-Si bonds and Si-X bonds (X represents a halogen atom) in the molecule, the reducing agent (B), and the solvent (C).

The polyhalosilane compound (A) used in the present invention contains a Si--Si bond and a Si--X bond (X represents a halogen atom) in the molecule.
The polyhalosilane compound (A) may be a cyclic compound or a chain compound containing a halogen atom and a silicon atom in the molecule.
The number of silicon atoms contained in the polyhalosilane compound (A) is not particularly limited, but is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more, and is preferably 8 or less, more preferably 7 or less, and even more preferably 6 or less.
When the polyhalosilane compound (A) is a chain compound, it may have a straight-chain structure or a branched structure.

Among these, it is more preferable that the polyhalosilane compound is a cyclic halosilane compound (a free cyclic halosilane compound). It is even more preferable that the cyclic halosilane compound has a structure (cyclic halosilane structure) in which silicon atoms are linked to form a monocyclic ring, and a halogen atom is bonded to at least one silicon atom constituting the monocyclic ring.

The number of silicon atoms constituting the monocyclic ring is not particularly limited, but is preferably 3 or more, more preferably 4 or more, even more preferably 5 or more, and is preferably 8 or less, more preferably 7 or less, and even more preferably 6 or less. The cyclic halosilane compound may contain silicon atoms that do not constitute a monocyclic ring, and for example, a silicon atom-containing substituent (e.g., a silyl group) may be bonded to a silicon atom constituting a monocyclic ring.

At least one halogen atom is preferably bonded to the monocyclic ring formed from silicon atoms, and more preferably, one or two (preferably two) halogen atoms are bonded to each of the silicon atoms constituting the monocyclic ring. The halogen atom is preferably a chlorine atom, a bromine atom, an iodine atom, or a fluorine atom, more preferably a chlorine atom or a bromine atom, and even more preferably a chlorine atom.
The free cyclic halosilane refers to a non-complex type cyclic halosilane such as Si ₅ Cl ₁₀ , Si ₆ Cl ₁₂ , or Si ₆ Cl ₁₁ H in which some of the halosilanes have been substituted with hydrogen atoms.

The polyhalosilane compound is preferably a reaction product of a salt of a cyclic halosilane compound with a Lewis acid (preferably a metal halide, more preferably a metal chloride, and even more preferably aluminum chloride), and the salt of the cyclic halosilane compound is preferably a compound represented by the following formula (1).

［上記式（１）において、Ｘ¹とＸ²はそれぞれ独立してハロゲン原子を表し、Ｌはアニオン性配位子を表し、ｐは配位子Ｌの価数として－２～０の整数（好ましくは－２又は－１の整数）を表し、Ｋは対カチオンを表し、ｑは対カチオンＫの価数として０～２の整数（好ましくは１又は２の整数）を表し、ｎは０～５の整数を表し、ａとｂとｃは０以上、“２ｎ＋６”以下の整数（ただし、ａ＋ｂ＋ｃ＝２ｎ＋６であり、ａとｃは同時に０ではない）を表し、ｄは０～３の整数（ただし、ａとｄは同時に０ではない）、ｅは０～３の整数（ただし、ｄ＋ｅ＝３）を表し、ｍは１～２であり、ｓは１以上の整数を表し、ｔは１以上の整数を表す。］

[In the above formula (1), ^X1 and ^X2 each independently represent a halogen atom, L represents an anionic ligand, p represents an integer of -2 to 0 (preferably an integer of -2 or -1) as the valence of the ligand L, K represents a counter cation, q represents an integer of 0 to 2 (preferably an integer of 1 or 2) as the valence of the counter cation K, n represents an integer of 0 to 5, a, b, and c represent integers of 0 or more and "2n+6" or less (provided that a+b+c=2n+6 and a and c are not 0 at the same time), d represents an integer of 0 to 3 (provided that a and d are not 0 at the same time), e represents an integer of 0 to 3 (provided that d+e=3), m is 1 to 2, s represents an integer of 1 or more, and t represents an integer of 1 or more.]

In formula (1), n defines the number of silicon atoms constituting the monocyclic ring, and its value is 0 to 5, preferably 1 or more, more preferably 2 or more, and preferably 4 or less, more preferably 3 or less. n is particularly preferably 3, i.e., it is preferably a 6-membered silicon monocyclic ring.

In formula (1), ^X1 represents a halogen atom bonded to a silicon atom constituting a ring, and ^X2 represents a halogen atom of a silyl group bonded to a silicon atom constituting a ring. Examples of the halogen atoms of ^X1 and ^X2 include a chlorine atom, a bromine atom, an iodine atom, and a fluorine atom, and preferably a chlorine atom and a bromine atom, and more preferably a chlorine atom. When there are multiple ^X1s , the multiple ^X1s may be the same or different. When there are multiple ^X2s , the multiple ^X2s may be the same or different.

In formula (1), a represents the number of halogen atoms bonded to silicon atoms constituting the ring, b represents the number of hydrogen atoms bonded to silicon atoms constituting the ring, and c represents the number of silyl groups bonded to silicon atoms constituting the ring. d represents the number of halogen atoms of the silyl groups bonded to silicon atoms constituting the ring, and e represents the number of hydrogen atoms of the silyl groups bonded to silicon atoms constituting the ring. When c is 2 or more, the multiple silyl groups bonded to silicon atoms constituting the ring may be the same or different. a, b, and c represent integers of 0 to 2n+6 (wherein a+b+c=2n+6 and a and c are not 0 at the same time), but it is preferable that a is an integer of 1 to 2n+6 and b and c are integers of 0 to n+5, and it is more preferable that a is an integer of n+6 to 2n+6 and b and c are integers of 0 to n. In addition, in the above formula (1), it is more preferable that c is 0, since it suppresses side reactions, improves the storage stability of the product, suppresses gas generation in the reduction process of the product compound, and increases the yield of the product compound. It is particularly preferable that a is 2n+6, and b and c are 0.

In formula (1), L represents an anionic ligand coordinated to the silicon atom constituting the ring, p represents the valence of the ligand (an integer of -2 to 0 (preferably an integer of -2 or -1)), and m represents the number of ligands (1 to 2). Examples of anionic ligands include halide ions, nitrate ions, and cyanide ions.

In formula (1), K represents a counter cation, q represents the valence of the counter cation K (an integer of 0 to 2 (preferably an integer of 1 or 2)), and the values of s and t are determined according to the valence and number of the ligand L and the valence of the counter cation K. Examples of the counter cation K include oniums (e.g., phosphonium ion and ammonium ion), polyamine.SiH ₂ Cl ⁺ (e.g., pedeta.SiH ₂ Cl ⁺ , theeda.SiH ₂ Cl ⁺ ), and the like. When the counter cation K is polyamine.SiH ₂ Cl ⁺ , spontaneous combustion gas may be generated, and therefore, in order to suppress the generation of such gas, it is preferable that the counter cation K is an onium. In addition, if the counter cation K is an onium, it is also preferable in terms of improving the yield of the product compound.

The onium of the counter cation K is preferably a phosphonium ion represented by the following formula (2) or an ammonium ion represented by the following formula (3): In formulas (2) and (3), R ¹ to R ⁴ and R ⁵ to R ⁸ each independently represent a hydrogen atom, an alkyl group, or an aryl group.

In formula (2), R ¹ to R ⁴ may be different from each other, but it is preferable that they are all the same group. In formula (3), R ⁵ to R ⁸ may be different from each other, but it is preferable that they are all the same group. As the alkyl group of ^{R 1} to R ⁴ and R ⁵ to R ⁸ , an alkyl group having 1 to 16 carbon atoms such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, or a cyclohexyl group is preferably mentioned, and an alkyl group having 1 to 8 carbon atoms is more preferable. As the aryl group of R ¹ to R ⁴ and R ⁵ to R ⁸ , an aryl group having 6 to 18 carbon atoms such as a phenyl group or a naphthyl group is preferably mentioned, and an aryl group having 6 to 12 carbon atoms is more preferable. Note that R ¹ to R ⁴ and R ⁵ to R ⁸ are preferably an alkyl group or an aryl group, and an aryl group is more preferable. If R ¹ to R ⁴ and R ⁵ to R ⁸ are aryl groups, the salt of the cyclic halosilane compound precipitates in the reaction solution during production of the salt of the cyclic halosilane compound, making it easier to obtain the salt of the cyclic halosilane compound with a high purity. For the same reason, as the onium of the counter cation K, a phosphonium ion is more preferable than an ammonium ion.

Specific examples of salts of the cyclic halosilane compound represented by formula (1) include salts of tetradecachlorocyclohexasilane dianion complex ([ _Si6Cl142- ^] ) and salts of _{tetradecabromocyclohexasilane} dianion complex ([ _Si6Br142- ^] ). The counter ion is preferably a phosphonium ion or an _ammonium ion.

As the salt of the cyclic halosilane compound represented by formula (1), it is preferable to use a compound represented by the following formula (4) or formula (5).

In the above formulas (4) and (5), X ¹ , R ¹ to R ⁴ , R ⁵ to R ⁸ , n and a are as defined above, and X ³ represents a halogen atom (in formulas (4) and (5), X ³ exists in an ionic form and is a halide ion).

The halogen atom of ^X3 includes a chlorine atom, a bromine atom, an iodine atom, and a fluorine atom, preferably a chlorine atom or a bromine atom, and more preferably a chlorine atom. When there are a plurality of ^X3 , the plurality of ^X3 may be the same or different. ^X1 and ^X3 may be the same or different.

In formula (4) and formula (5), n represents an integer of 0 to 5, and a represents an integer of 1 to 2n+6, with n being particularly preferably 3, and in this case, a is preferably 6 or more, more preferably 9 or more, and particularly preferably 12.

As a polyhalosilane compound, the cyclic halosilane compound is preferably a compound represented by the following formula (6).

式（６）中、Ｘ¹、Ｘ²、ａ～ｅ、ｎは上記と同じ意味を表す。

In formula (6), X ¹ , X ² , a to e, and n have the same meanings as above.

In formula (6), n is preferably 0 to 5, more preferably 1 or more, even more preferably 2 or more, and is preferably 4 or less, more preferably 3 or less. n is particularly preferably 3, i.e., a 6-membered silicon monocycle.

In formula (6), the halogen atoms of ^X1 and ^X2 include chlorine, bromine, iodine, and fluorine atoms, preferably chlorine and bromine atoms, and more preferably chlorine atoms. When there are multiple ^X1s , the multiple ^X1s may be the same or different. When there are multiple ^X2s , the multiple ^X2s may be the same or different.

In formula (6), a, b, and c represent integers from 0 to 2n+6 (where a+b+c=2n+6, and a and c are not 0 at the same time), but it is preferable that a is an integer from 1 to 2n+6, and b and c are integers from 0 to n+5, and it is more preferable that a is an integer from n+6 to 2n+6, and b and c are integers from 0 to n. It is particularly preferable that a is 2n+6, and b and c are 0.

The polyhalosilane compound (A) preferably contains a cyclic halosilane compound that does not contain a salt or a complex, more preferably contains a compound represented by formula (6), even more preferably contains dodecabromocyclohexasilane, dodecachlorocyclohexasilane, and even more preferably contains dodecachlorocyclohexasilane.
The polyhalosilane compound (A) may contain one or more of the above cyclic halosilane compounds.
In the polyhalosilane compound (A), a salt of a cyclic halosilane compound or a complex of a cyclic halosilane compound may be used in place of the cyclic halosilane compound.
The polyhalosilane compound (A) may be the reaction liquid used to prepare the polyhalosilane compound (A) as is, or may be a polyhalosilane compound that has been purified, or a polyhalosilane compound that has been dissolved in a predetermined solvent.

The polyhalosilane compound (A) may be a composition together with a solvent or the like (also referred to as the first composition). The content of the polyhalosilane compound (A) is preferably 1 to 80 mass%, more preferably 2 to 60 mass%, even more preferably 3 to 50 mass%, and particularly preferably 5 to 40 mass%, based on 100 mass% of the first composition. The remainder of the first composition may be the solvent described below.

The reducing agent (B) may be a composition together with a solvent and the like (also referred to as a second composition).
The content of the reducing agent (B) is preferably 5 to 80 mass%, more preferably 10 to 50 mass%, further preferably 15 to 40 mass%, particularly preferably 20 to 30 mass%, based on 100 mass% of the second composition (2). The remainder of the second composition may be a solvent, which will be described later.

The above polyhalosilane compound (preferably a cyclic halosilane salt, a free cyclic halosilane, a cyclic halosilane neutral complex, more preferably a free cyclic halosilane, etc.) is contacted with a reducing agent (reduction step) to prepare a hydrogenated polysilane compound.

The reducing agent (B) is not particularly limited, but it is preferable to use one or more types selected from the group consisting of aluminum-based reducing agents and boron-based reducing agents, and it is more preferable to use one or more types selected from the group consisting of aluminum hydride-based reducing agents and boron hydride-based reducing agents.

In the present invention, when the reducing agent (B) is an aluminum hydride-based reducing agent, the reducing agent (B) may be an aluminum hydride-based reducing agent having Al-R ¹ (R ¹ is an alkyl group which may be branched) or Al-OR ² (R ² is an alkyl group which may be branched).
Examples of ^R1 and ^R2 include linear alkyl groups such as a methyl group, an ethyl group, a butyl group, a propyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group; and branched alkyl groups such as an isopropyl group, an isobutyl group, a t-butyl group, a s-butyl group, a neopentyl group, and a (2-ethyl)hexyl group.
The number of carbon atoms in R ¹ and R ² is, for example, 1 to 10, preferably 1 to 8, more preferably 1 to 6, and further preferably 1 to 4.
The aluminum hydride reducing agent may have a plurality of R ¹ and R ² , and in that case, R ¹ and R ² may be the same or different.

Examples of aluminum-based reducing agents include metal hydrides such as lithium aluminum hydride (LiAlH ₄ ; LAH), diisobutylaluminum hydride (DIBAL), and sodium bis(2-methoxyethoxy)aluminum hydride ["Red-Al" (registered trademark of Sigma-Aldrich)].
Examples of the boron-based reducing agent include metal hydrides such as sodium borohydride and lithium triethylborohydride, and diborane. Among these, it is preferable to use metal hydrides, and it is more preferable to use diisobutylaluminum hydride. The reducing agent may be used alone or in combination of two or more.

In the present invention, from the viewpoints of preventing adhesion of solid residues to the wall surface of the vessel or piping even when the reaction system is used for a long period of time, reducing clogging and cleaning of the piping, and eliminating the need for solid-liquid separation, it is preferable that the reducing agent (B) and/or the reactant of the reducing agent (B) are liquid at a temperature of 30° C., the reducing agent (B) and the reactant of the reducing agent (B) are liquid at a temperature of 30° C., it is more preferable that the reactant of aluminum hydride having Al-R ¹ and the reactant of aluminum hydride having Al-R ¹ are liquid at a temperature of 30° C., and it is even more preferable that the reactant of diisobutylaluminum hydride and the reactant of diisobutylaluminum hydride are liquid at a temperature of 30° C.

In the present invention, the melting point of the reducing agent (B) is preferably 30° C. or lower, more preferably 25° C. or lower, even more preferably 20° C. or lower, still more preferably 15° C. or lower, particularly preferably 10° C. or lower, and is preferably −150° C. or higher or −100° C. or higher.
The melting point of the reaction product of the reducing agent (B) may be similar to the melting point of the reducing agent (B), but is preferably 70° C. or lower, more preferably 65° C. or lower, even more preferably 60° C. or lower, and even more preferably 55° C. or lower, and is preferably −110° C. or higher or −60° C. or higher.

The amount of reducing agent used may be set appropriately. For example, it is preferable that the equivalent of hydride in the reducing agent per silicon-halogen bond of the cyclic halosilane is at least 0.9 equivalents. The amount of the reducing agent used is more preferably 1.0 to 50 equivalents, even more preferably 1.0 to 30 equivalents, particularly preferably 1.0 to 15 equivalents, and most preferably 1.0 to 2 equivalents. If too much reducing agent is used, post-treatment takes time and productivity tends to decrease. On the other hand, if too little reducing agent is used, halogen remains unreduced, and yield tends to decrease.

The solvent (C) may be any organic solvent, and examples thereof include hydrocarbon solvents such as hexane and toluene; ether solvents such as diethyl ether, tetrahydrofuran, cyclopentyl methyl ether, diisopropyl ether, and methyl tertiary butyl ether. These organic solvents may be used alone or in combination of two or more. In addition, it is preferable that the solvent (C) contains a hydrocarbon solvent. The organic solvent solution obtained when producing a polyhalosilane compound (cyclic halosilane) may be used as the first composition as it is, or the organic solvent may be distilled off from the organic solvent solution containing the cyclic halosilane, and a new organic solvent may be added to obtain the first composition. In addition, it is preferable that the organic solvent used in the first composition and the second composition is purified, such as by distillation or dehydration, before the reaction in order to remove water and dissolved oxygen contained therein.
The solvent used in the first composition is more preferably a hydrocarbon-based solvent, and the solvent used in the second composition is more preferably a hydrocarbon-based solvent.

The amount of organic solvent used is preferably adjusted so that the concentration of the polyhalosilane compound (cyclic halosilane compound) is 0.01 to 1 mol/L, more preferably 0.02 to 0.7 mol/L, and even more preferably 0.03 to 0.5 mol/L. By carrying out the reaction within the above range, the content of impurities such as halogen elements contained in the composition containing the hydrogenated polysilane compound tends to be significantly reduced.

The concentration of the polyhalosilane compound (preferably a cyclic halosilane compound) in the first composition containing a solvent is preferably 0.01 mol/L or more, more preferably 0.02 mol/L or more, even more preferably 0.04 mol/L or more, and particularly preferably 0.05 mol/L or more. If the concentration of the polyhalosilane compound is too low, the amount of solvent increases, tending to reduce productivity. On the other hand, the upper limit of the concentration of the polyhalosilane compound is preferably 1 mol/L or less, more preferably 0.8 mol/L or less, and even more preferably 0.5 mol/L or less.

The lower limit of the temperature of the batch reactor is preferably -100°C or higher, more preferably -70°C or higher, even more preferably -20°C or higher, and even more preferably -0°C or higher. The upper limit of the temperature of the batch reactor is preferably +150°C or lower, more preferably +100°C or lower, even more preferably +50°C or lower, even more preferably +30°C or lower, and particularly preferably +20°C or lower. When the temperature is low, decomposition and polymerization of the intermediate product and the target product can be suppressed, so that the yield is improved. The reaction time may be appropriately determined depending on the amount of the first composition and the second composition used and the degree of progress of the reaction, and the time required to obtain the minimum amount of hydrogenated polysilane compound is usually 10 minutes or more and 30 hours or less, preferably 20 minutes or more and 15 hours or less, and more preferably 30 minutes or more and 5 hours or less.
The reaction time does not have to be within the above range, in which case the reaction may be allowed to proceed over time to prepare the desired product on a scale-up basis.

The hydrogenated polysilane compound (D) preferably contains cyclopentasilane or cyclohexasilane, and more preferably contains cyclohexasilane. The hydrogenated polysilane compound (D) may be pyrophoric.

The content of cyclohexasilane is preferably 97% by mass or more, more preferably 97.5% by mass or more, and even more preferably 98.0% by mass or more, based on 100% by mass of the hydrogenated polysilane compound (D). It is desirable that the content be as close to 100% by mass as possible, but it may be 99.9% by mass or less or 99.7% by mass or less.

The reactor is preferably equipped with a stirring device. When the reduction step of the polyhalosilane compound (A) and the mixing step with the acidic aqueous solution are performed in separate reactors, the reactor is also preferably equipped with a stirring device.

In the present invention, the hydrogenated polysilane compound (A) is produced in the following manner:

<Aspect (i)>
The hydrogenated polysilane compound (D) can be obtained by at least contacting the polyhalosilane compound (A) with the reducing agent (B) (preferably contacting the polyhalosilane compound (A), the reducing agent (B), and the solvent (C)) and then removing the reducing agent (B) and/or a reaction product of the reducing agent (B) (preferably a reaction product of the polyhalosilane compound (A) with the reducing agent (B) in the presence of the solvent (C)) by mixing with an acidic aqueous solution.
After mixing the reducing agent (B) and/or the reaction product of the reducing agent (B) with the acidic aqueous solution, it is preferable to subject the mixed liquid to separation and remove the layer containing the reducing agent (B) and/or the reaction product of the reducing agent (B) to obtain a layer containing a hydrogenated polysilane compound (D).
The separation may be any operation that extracts or removes a layer containing a desired substance from the resulting multiple layers, and examples of the operation include separation by decantation and separation using a funnel.

<Aspect (ii)>
The hydrogenated polysilane compound (D) can be obtained by contacting at least the polyhalosilane compound (A) with the reducing agent (B) (preferably contacting the polyhalosilane compound (A), the reducing agent (B), and the solvent (C)) and then subjecting the resulting contact mixture to distillation.
The mixture after contact is preferably subjected to reduced pressure or heating to remove the solvent, and the composition from which the solvent has been removed is preferably distilled (preferably distilled under reduced pressure) as described below.

<Aspects (i) and (ii)>
The hydrogenated polysilane compound (D) can be obtained by contacting at least the polyhalosilane compound (A) with the reducing agent (B) (preferably contacting the polyhalosilane compound (A), the reducing agent (B), and the solvent (C)), removing the reducing agent (B) and/or the reaction product of the reducing agent (B) by mixing with an acidic aqueous solution, and subjecting the resulting solution to distillation.
After mixing the reducing agent (B) and/or the reactant of the reducing agent (B) with the acidic aqueous solution, the mixed liquid is subjected to separation to remove the layer containing the reducing agent (B) and/or the reactant of the reducing agent (B) to obtain a layer containing a hydrogenated polysilane compound (D), and the layer is preferably subjected to reduced pressure or heating as necessary to evaporate off the solvent and distill.
In the embodiment including (ii) above, the filtration step may not be carried out.

In the embodiment including (i) above, when the reducing agent (B) and/or the reaction product of the reducing agent (B) is contacted with the acidic aqueous solution, it is preferable to drop at least one of the reducing agent (B) and/or the reaction product of the reducing agent (B) and the acidic aqueous solution. By dropping one or both of the reducing agent (B) and/or the reaction product of the reducing agent (B) and the acidic aqueous solution in this manner, the reducing agent (B) and/or the reaction product of the reducing agent (B) can be decomposed with almost no solid residue formed, and the generated heat can be suppressed by the dropping speed, etc., which leads to an effect of improving productivity.

In the embodiment including the above (i), there are three preferred embodiments in which the reducing agent (B) and/or the reactant of the reducing agent (B) and/or the acidic aqueous solution are dropped. That is, A) a reactor is charged with the reducing agent and/or the reactant of the reducing agent, and the acidic aqueous solution is dropped thereto, B) a reactor is charged with the acidic aqueous solution, and the reducing agent and/or the reactant of the reducing agent are dropped thereto, and C) a reactor is simultaneously or sequentially dropped with the reducing agent and/or the reactant of the reducing agent and the acidic aqueous solution. Among these, the above embodiment B) is preferred, that is, it is preferred to drop the reducing agent and/or the reactant of the reducing agent into the acidic aqueous solution.

The acidic aqueous solution may be an aqueous solution of hydrochloric acid, nitric acid, sulfuric acid, etc. A preferred acidic aqueous solution is an aqueous solution of sulfuric acid.
The concentration of the acidic aqueous solution is, for example, 0.1 to 25% by mass, preferably 0.5 to 20% by mass, and more preferably 1 to 15% by mass.
The amount of the acidic aqueous solution used may be adjusted to preferably 100 to 10,000 parts by mass, more preferably 200 to 5,000 parts by mass, and even more preferably 300 to 3,000 parts by mass, relative to 100 parts by mass of the reducing agent (B) and/or the reactant of the reducing agent (B).

The reducing agent and/or the reactant of the reducing agent is decomposed by mixing the reducing agent and/or the reactant of the reducing agent with an acidic aqueous solution. The mixture may be separated into an aqueous phase and an organic phase (also called an oil layer), and the organic phase may be separated to extract a solution containing the hydrogenated polysilane compound by liquid separation.

In the embodiment including (ii) above, the solution containing the hydrogenated polysilane compound is further purified by distillation. If necessary, the solution containing the hydrogenated polysilane compound may be concentrated, and then the highly concentrated hydrogenated polysilane compound (preferably cyclohexasilane) may be distilled. This distillation is preferably reduced pressure distillation. There are no particular limitations on the method of reduced pressure distillation, and it may be performed using a known distillation column, and may be performed under light-shielding conditions. The above distillation is preferably performed by dividing the fraction into a plurality of fractions, and only the appropriate fraction may be selected from the obtained fractions.

In particular, the distillation (particularly reduced pressure distillation) may be carried out two or more times. For example, a solution containing a hydrogenated polysilane compound may be distilled under reduced pressure to recover a fraction having an appropriate content of cyclic silane hydrogen (particularly cyclohexasilane) (first distillation), and the recovered fraction may then be distilled under reduced pressure again to recover a fraction having an appropriate content of cyclic silane hydrogen (particularly cyclohexasilane) (second distillation), and the second distillation may be repeated as necessary.
The conditions for distillation (preferably reduced pressure distillation) include a temperature of preferably 20 to 80° C., more preferably 30 to 65° C., and a pressure of preferably 5 to 400 Pa, more preferably 10 to 350 Pa, and even more preferably 10 to 300 Pa.

The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is of course possible to carry out the invention with appropriate modifications within the scope of the purpose described above and below, and all such modifications are included in the technical scope of the present invention. In the following, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

Example 1
After replacing the inside of a 300 mL three-neck flask equipped with a dropping funnel and a stirrer with nitrogen, 24.5 g of a 7% by weight hexane solution of dodecachlorocyclohexasilane was added. While stirring the solution in the flask, 40 mL of a 1.0 mol/L diisobutylaluminum hydride-hexane solution (manufactured by WAKO) was gradually dropped from the dropping funnel as a reducing agent under 0°C conditions, and then stirred at room temperature for 3 hours. After the reaction, the reaction solution was slowly dropped into 100 mL of a degassed 10% by weight aqueous sulfuric acid solution to inactivate the reaction. The oil layer was taken out by liquid separation, dehydrated with magnesium sulfate, filtered, and analyzed by gas chromatography, and the yield of cyclohexasilane was 78%. No solid precipitation was observed during the reaction or during inactivation. After the solvent was distilled off from this oil layer, cyclohexasilane was isolated by vacuum distillation at 35°C and 200 Pa.

Comparative Example 1
A 100 mL three-neck flask equipped with a dropping funnel and a stirrer was charged with 100.0 g of a 10% by mass dodecachlorocyclohexasilane hexane solution. After replacing the atmosphere in the flask with nitrogen gas, 38 mL of a diethyl ether solution of lithium aluminum hydride (concentration: about 1.0 mol/L) was gradually dropped from the dropping funnel as a reducing agent under 0°C while stirring the solution in the flask, and then the reduction reaction was carried out by stirring at 20°C for 3 hours. After the reaction, precipitation of a white solid was observed. The resulting reaction solution was filtered under a nitrogen atmosphere to remove the generated salt, and the obtained filtrate was analyzed using gas chromatography, confirming that cyclohexasilane was generated (yield 90%).

Claims (5)

A method for producing a cyclic hydrogenated polysilane compound (D) from a composition containing a free cyclic halosilane compound (A) containing a Si-Si bond and a Si-X bond (X represents a halogen atom) in the molecule and not containing a salt , a reducing agent (B), and a solvent (C), comprising the steps of:
The reducing agent (B) and/or the reactant of the reducing agent (B) are liquid at a temperature of 30° C.;
(i) a step of contacting the free cyclic halosilane compound (A) not containing the salt with the reducing agent (B) and then removing the reducing agent (B) and/or the reaction product of the reducing agent (B) by mixing with an acidic aqueous solution; and/or
(ii) extracting the cyclic hydrogenated polysilane compound (D) by distillation;
2. A method for producing a cyclic hydrogenated polysilane compound, comprising: 2. The method for producing a cyclic hydrogenated polysilane compound according to claim 1, wherein the reducing agent (B) is either aluminum hydride or boron hydride. 3. The method for producing a cyclic hydrogenated polysilane compound according to claim 1 or 2, wherein the reducing agent (B) is an aluminum hydride having Al-R ¹ (R ¹ is an alkyl group which may be branched) or Al-OR ² (R ² is an alkyl group which may be branched ). The method for producing a cyclic hydrogenated polysilane compound according to any one of claims 1 to 3, wherein the solvent (C) contains a hydrocarbon solvent. The method for producing a cyclic hydrogenated polysilane compound according to any one of claims 1 to 4, wherein the cyclic hydrogenated polysilane compound (D) contains cyclopentasilane or cyclohexasilane.