Background
The biodegradable high polymer materials are many, Polyhydroxybutyrate (PHB) is one of the most common natural biodegradable polyesters, the monomer beta-butyrolactone of the polyhydroxybutyrate is derived from renewable crops such as corn and potato, and solid waste generated after the polyester product is used can be degraded through biological fermentation to generate carbon dioxide and water, so that the biodegradable high polymer material is an ideal green and environment-friendly material. Moreover, the polymer has high thermoplastic and mechanical properties, and can be compared with polypropylene materials. However, PHB still faces many problems as a green commercial thermoplastic due to the limitations of high cost and low yield of the biotechnological production of PHB. Therefore, chemical synthesis of PHB is particularly important, wherein the simplest synthesis method is to catalyze rac-beta-butyrolactone (rac-BBL) to carry out ring-opening polymerization to obtain PHB.
The amido bisphenol rare earth metal complex has good performance in catalyzing ring-opening polymerization of cyclic ester monomers, can efficiently carry out ring-opening polymerization of the cyclic ester monomers, has unusual selectivity and simultaneously has good controllability, so that the preparation of the amido bisphenol rare earth metal complex and the research on the catalytic performance thereof arouse extensive interest of people.
In 2006, the Carpentier project combined a series of methoxy amino bridged bisphenol yttrium complexes with different substituents, and studied the influence of the difference of the substituents on phenol on the ring-opening polymerization result of the catalyzed racemic lactide. It was found that when the substituents were changed from methyl to the bulky substituents tert-butyl, adamantyl and 2-phenylisopropyl, there was no significant change in catalytic activity, but there was a significant effect on the microstructure of the polylactic acid. When the substituent is cumyl substituted, the degree of syndiotacticity reaches a maximum. See document 1(Amgoune A, Thomas C M, Roisnel T, et al. Ring-influencing polymerization of lactic with group 3. metallic compounds supported by binary alkoxy-amino-bisphenolate ligands: combining high activity, and activity [ J ]. Chemistry-A European Journal,2006,12(1): 169.).
In 2009, Kol subject group reported a chiral diamine-bridged bisphenol ligand consisting of bistetrahydropyrrole, based on which metal aluminum complexes and lanthanide metal complexes were prepared, respectively, and they found that the corresponding metal complexes can initiate the controlled stereoselective ring-opening polymerization of racemic lactide, and that the obtained polylactide had high syndiotactic and isotactic and had the characteristics of narrow molecular weight distribution and high molecular weight. See document 2(, (a)Sergeeva E,KopilovJ,Goldberg I,et al.Salan ligands assembled around chiral bipyrrolidine:predetermination of chirality around octahedral Ti and Zr centres[J].Chemical communications,2009(21):3053-3055.(b)Press K,Goldberg I,Kol M.Mechanistic insight into the stereochemical control of lactide polymerization by salan-aluminum catalysts[J].Angewandte Chemie International Edition,2015,54(49):14858-14861.(c)Beament J,

G,Jones M D,et al.Bipyrrolidine salan alkoxide complexes of lanthanides:synthesis,characterisation,activity in the polymerisation of lactide and mechanistic investigation by DOSY NMR[J].Dalton Transactions,2018,47(27):9164-9172.)。
In 2009, the Coates topic group reports an isopropoxy complex of dimethylamino-bridged bisphenol yttrium, which is used for catalyzing rac-BBL ring-opening polymerization, shows high activity and better controllability, and the obtained polymer has high syndiotactic degree. See document 3(Kramer J W, Treitler D S, Dunn E W, et al.polymerization of aromatic monomers using synthetic copolymers in polymer synthesis, [ J ]. Journal of American Chemical Society,2009,131(44): 16042-.
In 2015, the YaoYingming subject combined a series of diamino bridged bisphenol yttrium guanidyl complexes, and performed ring-opening polymerization research on catalyzed racemic lactide and rac-beta-butyrolactone. The complexes can well catalyze the ring-opening polymerization of rac-lactide and rac-beta-butyrolactone. See, e.g., document 4(Zeng T, Qian Q, ZHao B, et al. Synthesis and catalysis of ray-earth metal peptides stabilized by amine-bridged bis (phenolate) ligands and the use of ray-lactate and ray- β -butylrolactone [ J ]. RSC Advances,2015,5(65):53161 and 53171.).
The catalyst of the diamino bridged bisphenol rare earth metal complex has good performance in catalyzing ring-opening polymerization of cyclic ester monomers. In particular, polyhydroxybutyrate with different selectivity can be obtained in the catalysis of rac-beta-butyrolactone, and polyhydroxybutyrate with different selectivity can be applied to the fields of medical treatment, chemical industry, environmental protection, aerospace and the like. However, the ring-opening polymerization rate of the related prior art still needs to be improved, the preparation method is relatively complex, and the yield is not ideal enough.
Disclosure of Invention
In order to solve the problems of the prior art, the invention aims to overcome the defects of the prior art and provide a tetrahydropyrrole diamino bridged bisphenol rare earth metal complex, and preparation and application thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
a pyrrolidine diamine-bridged bisphenol rare earth metal complex has a chemical structural formula shown as the following formula I:
wherein Ln is a rare earth metal; r1And R2Respectively selected from any one of tert-butyl, cumyl and triphenyl.
Preferably, Ln is any one of yttrium, lanthanum and gadolinium.
The invention relates to a preparation method of a pyrrolidine diamino bridged bisphenol rare earth metal complex, which comprises the following steps:
(1) synthesizing a ligand intermediate product, wherein the chemical structural formula of the ligand intermediate product is shown as the following formula II:
(2) reacting the ligand intermediate synthesized in the step (2) with Ln [ N (SiHMe)2)2]3(THF)nReaction to obtain a pyrrolidine diamine bridgeA bisphenol rare earth metal complex.
Preferably, in the step (2), Ln is any one of yttrium, lanthanum and gadolinium.
Preferably, the step (2) includes the steps of
(2-1) reacting the ligand intermediate product with Ln [ N (SiHMe) under anhydrous and anaerobic conditions2)2]3(THF)nThe molar ratio of the raw materials is 1: 1 in a solvent, reacting for at least 18h, and then vacuum-drying the solvent to obtain a crude product;
(2-2) dissolving the crude product by using an anhydrous toluene solvent, adding anhydrous n-hexane to prepare a saturated solution, and recrystallizing at the temperature of not higher than-30 ℃ to obtain a white solid, namely the pyrrolidine diamine bridged bisphenol rare earth metal complex.
Preferably, in the step (2-1), the solvent is at least one of an anhydrous toluene solvent and an anhydrous n-hexane solvent.
Preferably, in the step (2-1), the reaction temperature is a normal temperature condition of 20 to 25 ℃.
The application of the pyrrolidine diamine-based bridged bisphenol rare earth metal complex disclosed by the invention in preparing polyhydroxybutyrate by using the pyrrolidine diamine-based bridged bisphenol rare earth metal complex disclosed by the invention as a raw material comprises the following steps of:
a. mixing a tetrahydropyrrole diamine-bridged bisphenol rare earth metal complex and a rac-beta-butyrolactone monomer in a solvent according to a molar ratio of 1 (200-1000) to obtain a mixed solution;
b. and carrying out ring-opening polymerization reaction on the mixed solution at the temperature of not less than 25 ℃ to obtain polyhydroxybutyrate.
Preferably, in the step a, the solvent employs at least one of toluene and n-hexane.
Compared with the prior art, the invention has the following obvious and prominent substantive characteristics and remarkable advantages:
1. the compound is a diamine-bridged bisphenol rare earth metal complex, and the diamine-bridged ligand and the rare earth metal exist, so that the compound has higher catalytic activity in the catalytic ring-opening polymerization reaction;
2. the preparation method of the complex utilizes an intermediate ligand compound and Ln [ N (SiHMe)2)2]3(THF)nThe reaction is carried out in a solvent to obtain the tetrahydropyrrole diamino bridged bisphenol rare earth metal complex which has higher catalytic activity and is easy to prepare, and the obtained product has-NSiHMe2And rare earth metal, the ring-opening polymerization rate can be improved, and the conditions required by the reaction are milder;
3. the invention realizes the improvement of the ring-opening polymerization rate, and the preparation method is simpler and easier to control, and has high yield and low cost.
Detailed Description
The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below:
the first embodiment is as follows:
a method for preparing LYNSiHMe2(R1=tBu,R2=CPh3) The method comprises the following steps:
(1) before preparing the pyrrolidine diamine-bridged bisphenol rare earth metal complex, a ligand L3 is prepared, and the preparation method comprises the following steps:
synthesis of ligand L3: putting N-benzyl-2-tetrahydropyrrole methylamine and 4-tert-butyl-2-trisphenol into a round-bottom flask, adding isopropanol, stirring and dissolving, and then adding N-benzyl-2-tetrahydropyrrole methylamine and paraformaldehyde into a mixture of 1: 2, adding paraformaldehyde into a round-bottom flask, heating to 90 ℃, stirring at 90 ℃ for reaction for 48 hours, stopping the reaction, recovering room temperature, separating out solid powder, spin-drying an organic reagent to obtain a crude product, performing column chromatography separation on the crude product, wherein the eluent uses petroleum ether: the volume ratio of ethyl acetate is 10: 1, finally obtaining a white solid with the yield of 80 percent, and heating and drying the obtained white solid at 65 ℃ to remove water for preparing the rare earth metal complex, which is shown in figure 1;
(2) preparation of LYNSiHMe2(R1=tBu,R2=CPh3):
Weighing a certain amount of Y [ N (SiHMe) in a glove box filled with high-purity nitrogen protection2)2]3(THF)2Dissolving N-hexane in round-bottom flask, adding ligand L3 and Y [ N (SiHMe) in round-bottom flask2)2]3(THF)2Is 1: weighing dried ligand L3 according to the molar ratio of 1, adding toluene with half amount of n-hexane for dissolving, slowly dripping into n-hexane solution, stirring at normal temperature for 18 hours, stopping reaction, draining the solvent, dissolving solid powder with trace amount of toluene, adding a proper amount of n-hexane to prepare saturated solution, putting into a refrigerator for recrystallization to obtain solid powder, namely pyrrolidine diamino bridged bisphenol rare earth metal complex LYNSiHMe2(R1=tBu,R2=CPh3) And the yield is 60%. See fig. 2.
Example two:
preparation of LLaNSiHMe2(R1=tBu,R2=CPh3) The method comprises the following steps:
the step (1) of the present embodiment is the same as the first embodiment; step (2) weighing a certain amount of La [ N (SiHMe)2)2]3(THF)2And then weighing and mixing with La [ N (SiHMe)2)2]3(THF)2Ligand L3 in equimolar ratio. After the reaction is finished, recrystallizing to obtain solid powder, namely the pyrrolidine diamine-based bridged bisphenol rare earth metal complex LLaNSiHMe2(R1=tBu,R2=CPh3) The yield was 61%.
Example three:
preparation of LGdNSiHMe2(R1=tBu,R2=CPh3)
The step (1) of the present embodiment is the same as the first embodiment; weighing a certain amount of Gd [ N (SiHMe)2)2]3(THF)2And weighing the mixture with Gd [ N (SiHMe)2)2]3(THF)2Ligand L3 in equimolar ratio. After the reaction is finished, solid powder is obtained by recrystallization, namely the pyrrolidine diamine-bridged bisphenol rare earth metal complex LGdNSHMe2(R1=tBu,R2=CPh3) The yield was 62%.
Example four:
a method for preparing LYNSiHMe2(R1=Cumly,R2=Cumly)
1) In the preparation of LYNSiHMe2(R1=Cumly,R2Cumly), ligand L2 was prepared as follows:
synthesis of ligand L2: putting N-benzyl-2-tetrahydropyrrole methylamine and 2, 4-dicumyl phenol into a round-bottom flask, adding methanol, stirring and dissolving, and then adding N-benzyl-2-tetrahydropyrrole methylamine and formaldehyde into a mixture of 1: weighing water formaldehyde according to the molar ratio of 18, adding the water formaldehyde into a round-bottom flask, heating to 65 ℃, stirring at 65 ℃ for reaction for 48 hours, stopping the reaction, recovering the room temperature, separating out solid powder, spin-drying an organic reagent to obtain a crude product, performing column chromatography separation on the crude product, wherein an eluent uses petroleum ether: the volume ratio of ethyl acetate is 10: 1 to finally obtain white solid with the yield of 80 percent, and heating and drying the obtained white solid at 65 ℃ to remove water so as to prepare the rare earth metal complex;
2) preparation of LYNSiHMe2(R1=Cumly,R2=Cumly)
Weighing a certain amount of Y [ N (SiHMe) in a glove box filled with high-purity nitrogen protection2)2]3(THF)2Adding appropriate amount of N-hexane into round-bottom flask, dissolving, adding ligand L2 and Y [ N (SiHMe) into round-bottom flask2)2]3(THF)2Is 1: weighing dried ligand L2 according to the molar ratio of 1, adding toluene with half amount of n-hexane for dissolving, and slowly dropwise adding n-hexaneStirring in alkane solution at normal temperature for 18 hr, stopping reaction, draining off solvent, dissolving solid powder with trace amount of toluene, adding n-hexane to obtain saturated solution, and recrystallizing in refrigerator to obtain solid powder, i.e. pyrrolidine diamino bridged bisphenol rare earth metal complex LYNSiHMe2(R1=Cumly,R2Cumly) yield 63%. See fig. 3.
Example five:
preparation of LYNSiHMe2(R1=tBu,R2=tBu)
1) In the preparation of LYNSiHMe2(R1=tBu,R2=tBu), ligand L1 was prepared as follows:
synthesis of ligand L1: putting N-benzyl-2-tetrahydropyrrole methylamine and 2, 4-di-tert-butylphenol into a round-bottom flask, adding a proper amount of methanol, stirring and dissolving, and then adding N-benzyl-2-tetrahydropyrrole methylamine and formaldehyde into a mixture of 1: weighing water formaldehyde according to the molar ratio of 18, adding the water formaldehyde into a round-bottom flask, heating to 65 ℃, stirring at 65 ℃ for reaction for 48 hours, stopping the reaction, recovering the room temperature, separating out solid powder, spin-drying an organic reagent to obtain a crude product, performing column chromatography separation on the crude product, wherein an eluent uses petroleum ether: the volume ratio of ethyl acetate is 10: 1 to finally obtain white solid with the yield of 80 percent, and heating and drying the obtained white solid at 65 ℃ to remove water so as to prepare the rare earth metal complex;
2) preparation of LYNSiHMe2(R1=tBu,R2=tBu)
Weighing a certain amount of Y [ N (SiHMe) in a glove box filled with high-purity nitrogen protection2)2]3(THF)2Adding appropriate amount of N-hexane into round-bottom flask, dissolving, adding ligand L1 and Y [ N (SiHMe) into round-bottom flask2)2]3(THF)2Is 1: weighing dried ligand L1 at a molar ratio of 1, adding toluene with half amount of n-hexane for dissolving, slowly dripping into n-hexane solution, stirring at normal temperature for 18 hours, stopping reaction, draining solvent, dissolving solid powder with trace amount of toluene, and adding appropriate amount of n-hexanePreparing hexane into saturated solution, recrystallizing in refrigerator to obtain solid powder, i.e. pyrrolidine diamino bridged bisphenol rare earth metal complex LYNSiHMe2(R1=tBu,R2=tBu) yield 60%.
Example six:
LYNSiHMe2(R1=tBu,R2=tBu) catalyzes rac-beta-butyrolactone to carry out ring-opening polymerization, and comprises the following steps:
a5 mL vial filled with a high purity nitrogen blanket was charged with 0.01 mmole LYNSiHMe2(R1=tBu,R2=tBu) complex, 172 mg of rac-beta-butyrolactone were added to the toluene solution, stirred at 25 ℃ for 60min, and the reaction was stopped with 5% hydrochloric acid in methanol;
the polymer was precipitated with methanol and dried under vacuum to a constant weight of polyhydroxybutyrate of 110 mg, 64% yield and 68% syndiotactic content.
Example seven:
LYNSiHMe2(R1=Cumly,R2Cumly) catalyzes the ring-opening polymerization of rac- β -butyrolactone by the following steps:
a5 mL vial filled with a high purity nitrogen blanket was charged with 0.01 mmole LYNSiHMe2(R1=Cumly,R2Cumly) was added to the toluene solution, 172 mg of rac- β -butyrolactone was added to the toluene solution, and after stirring at 25 ℃ for 50min, the reaction was terminated with 5% hydrochloric acid in methanol;
the polymer was precipitated with methanol and dried under vacuum to a constant weight of 138 mg polyhydroxybutyrate in 80% yield and a syndiotactic content of 68%.
Example eight:
LYNSiHMe2(R1=tBu,R2=CPh3) Catalyzing the ring opening polymerization of rac-beta-butyrolactone, and the steps are as follows:
a5 mL vial filled with a high purity nitrogen blanket was charged with 0.01 mmole LYNSiHMe2(R1=tBu,R2=CPh3) Adding 172 mg of rac-beta-butyrolactone in the toluene solution of the complex, stirring for 10min at 25 ℃, and terminating the reaction by using methanol containing 5% hydrochloric acid;
the polymer was precipitated with methanol and dried under vacuum to give 168 mg of polyhydroxybutyrate of constant weight, 97% yield and 91% syndiotactic content. See fig. 4.
Example nine:
LGdNSiHMe2(R1=tBu,R2=CPh3) Catalyzing the ring opening polymerization of rac-beta-butyrolactone, and the steps are as follows:
a5 mL glass vial filled with a high purity nitrogen protected glove box was charged with 0.01 mmol LGdNSAIHMe2(R1=tBu,R2=CPh3) Adding 172 mg of rac-beta-butyrolactone in the toluene solution of the complex, stirring for 15min at 25 ℃, and terminating the reaction by using methanol containing 5% hydrochloric acid;
the polymer was precipitated with methanol and dried under vacuum to give a constant weight of polyhydroxybutyrate 161 mg, 93% yield and a syndiotactic content of 88%.
Through the above examples, it can be demonstrated that the tetrahydropyrrole diamine-based bridged bisphenol rare earth metal complex in the above examples is convenient to synthesize. The tetrahydropyrrole diamino bridged bisphenol rare earth metal complex used as a catalyst in the embodiment has high activity of catalyzing the ring-opening polymerization of rac-beta-butyrolactone, and the molar ratio of rac-beta-butyrolactone to the catalyst can reach 1000: 1; in addition, the catalyst has good selectivity for catalyzing rac-beta-butyrolactone, and polyhydroxybutyrate is mainly syndiotactic. The complex of the embodiment has rare earth elements and a pyrrolidine diamine bridged ligand, can effectively catalyze the ring-opening reaction, and has the advantages of high reaction rate, high activity and mild reaction conditions. The preparation method of the compound of the embodiment and the application of the compound in preparing biodegradable high molecular material Polyhydroxybutyrate (PHB).
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made according to the purpose of the invention, and any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention should be replaced with equivalents as long as the object of the present invention is met, and the technical principle and the inventive concept of the present invention are not departed from the scope of the present invention.