阳离子型稀土金属配合物催化烯烃聚合的理论研究
发布时间：2018-11-27 12:11
【摘要】：高性能烯烃聚合催化剂的发展已成为新型聚烯烃材料发展的主要推动力。近年来,阳离子型稀土金属配合物在烯烃聚合中表现出了独特的催化性能,从而受到国内外研究者的广泛关注。然而现有实验手段难以检测和分离相关催化过程的活性物种,妨碍了有关聚合机理等基本化学问题的探讨。运用理论计算化学方法可以从分子水平上研究反应机理,在很大程度上推动了新型聚烯烃催化剂及新型聚合材料的发展。本论文采用QM(Quantum Mechanics)和ONIOM计算方法从分子水平上探讨了一系列稀土金属配合物催化烯烃聚合的反应机理,包括金属和辅助配体影响聚合活性与选择性的分子机制等基本化学问题。主要研究结果如下：1.对含C3对称性iPr-triSOX配体的阳离子型稀土金属烷基配合物催化1-己烯全同聚合过程进行了计算研究。结果表明,在链引发和链增长阶段,2,1-插入的过渡态中辅助配体和1-己烯的(CH2)3CH3链之间存在较大的相互排斥作用,而1,2-插入不存在此作用,因此,1,2-插入成为动力学上更有利的插入方式；1-己烯的全同聚合主要为动力学控制过程,遵循链端控制机理；二价阳离子活性物种催化的聚合过程在动力学和热力学上均优于一价物种,计算结果与实验结果一致。金属钪物种催化的1-己烯插入过程在动力学上比钇物种更有利,且阳离子钪物种比对应的钇物种更容易生成,从而解释了阳离子钪配合物具有高活性的原因。2.对阳离子型稀土金属配合物[(η5-C5Me5)Ln(CH2SiMe3)(THF)n]+(A,Ln=Sc,Y,Lu, Gd, Sm； n = 0 (AL.),1 (thfALn))、[(η5-C5Me5)Sc(CH2C6H4NMe2-0)]+ (B)和[(η5-C5Me5)Sc(C6H4OMe-0)]+(C)催化苯乙烯聚合过程中的区域选择性、立体选择性、内外源Lewis碱对链端微结构的影响以及不同金属的催化活性进行了计算研究。结果表明,外源Lewis碱THF不影响聚苯乙烯的选择性,但能够降低聚合活性；氨基苄基内源Lewis碱,能够降低链引发过程的区域选择性,对链增长的立体选择性无明显影响；甲氧苯基作为内源Lewis碱时,金属钪原子与氧原子之间的强相互作用倾向于得到全同的链端微结构。首次阐明钪金属配合物具有较高活性的原因在于钪具有较强Lewis酸性、较小的离子半径以及聚合过程不容易进入休眠态等。3.对含有不同配体的金属钪配合物催化戊二烯、丁二烯和异戊二烯立体选择性聚合过程进行了计算研究。结果表明,在戊二烯聚合过程中,顺式-1,4单体插入过程在动力学上明显优于反式-1,4单体的插入过程；全同立构聚合在动力学和热力学上均比间同立构聚合容易发生；全同立构聚合过程中配体和单体之间存在较大的排斥作用,是导致间同选择性聚合较难发生的主要原因。在丁二烯聚合过程中,顺式-1,4选择性主要归因于对应过渡态中单体与金属中心间的较强相互作用；相比之下,异戊二烯1,4插入过渡态中单体与辅助配体之间存在较明显的相互排斥作用,从而有利于异戊二烯的3,4-选择性聚合。4.对阳离子型镧-铝双金属配合物催化的异戊二烯反式-1,4-聚合机理进行了计算研究。结果表明,在三种’可能存在的活性物种[(C5Me5)La(μ2-Me)3AlMe]+(A). [(C5Me5)La(μ2-Me)2AlMe2]+(B)和[(C5Me5)La(Me)(μ2-Me)AlMe2]+(C)中,通过探讨链引发、三种物种的相互转化以及烯烃配位分离抗衡阴离子的过程,发现物种C可能是催化合成反式-1,4聚异戊二烯的真实活性物种；通过对镧-铝双金属中心协同催化以及金属镧单中心催化聚合路径进行对比,发现后一种路径是更加有利的聚合过程。在单金属中心催化聚合过程中,AlMe3作为配体通过一个甲基与金属镧中心配位；与镧不同,以金属钇为中心的聚合体系中,AlMe配体在聚合过程中趋于远离金属钇中心,从而得到顺式-1,4聚异戊二烯,与实验结果一致,金属镧与钇催化体系在聚合选择性上的差异主要源于金属钇比金属镧离子半径小以及AlMe在热力学上易于从钇金属中心解离。上述结果表明,烷基铝对此聚合体系的选择性起到了至关重要的作用。
[Abstract]:The development of high-performance olefin polymerization catalyst has become the main driving force for the development of a new type of polyolefin material. In recent years, cationic rare-earth metal complexes show a unique catalytic performance in the polymerization of olefins, which are of great concern to the researchers at home and abroad. However, the existing experimental means is difficult to detect and separate the active species of the relevant catalytic process, which is an obstacle to the discussion of the basic chemical problems such as the polymerization mechanism. By using the theory, the reaction mechanism can be studied from the molecular level, and the development of the new type of polyolefin catalyst and the new type of polymeric material is promoted to a great extent. In this paper, the reaction mechanism of a series of rare-earth metal complexes to catalyze the polymerization of olefins, including the effects of metals and auxiliary ligands, on the polymerization activity and the molecular mechanism of selective molecular mechanism, is discussed from the molecular level by using the QM (Quantum Mechanics) and the ONIOM calculation method. The main results are as follows: 1. The polymerization of 1-hexene with the cation-type rare-earth metal alkyl complex containing the C3-symmetric iPr-trisox ligand was studied. The results show that there is a large mutual exclusion between the auxiliary ligand and the (CH2) 3CH3 chain of 1-hexene in the transition state of the chain initiation and the chain growth. The whole-homopolymerization of 1-hexene is mainly the kinetic control process, followed by the chain end control mechanism, and the polymerization process catalyzed by the divalent cation active species is better than the one-valent species in the dynamics and thermodynamics, and the calculation results are consistent with the experimental results. the 1-hexene insertion process catalyzed by a metal-based species is more advantageous in kinetics than in the native species, and the cationic species is more easily generated than the corresponding species of the species, thus explaining the reason for the high activity of the cationic polymer complex. The regioselectivity and stereoselectivity of the cationic rare-earth metal complex[(H5-C5Me5) Ln (CH2SiMe3) (THF) n] + (A, Ln = Sc, Y, Lu, Gd, Sm; n = 0 (AL.), 1 (thfALn)),[(H5-C5Me5) Sc (CH2C6H4NMe2-0)] + (B) and[(-5-C5Me5) Sc (C6H4OMe-0)] + (C) in the catalytic styrene polymerization process, The effect of the internal and external sources of Lewis base on the microstructure of the chain end and the catalytic activity of different metals were studied. The results show that the exogenous Lewis base THF does not affect the selectivity of the polystyrene, but can reduce the polymerization activity; the amino-base endogenous Lewis base can reduce the regioselectivity of the chain initiation process, has no obvious effect on the stereoselectivity of the chain growth, The strong interaction between the metal atom and the oxygen atom tends to result in a fully-identical chain-end microstructure. The reason for the first time that the metal complex has higher activity is that it has a strong Lewis acidity, a smaller ionic radius, and the polymerization process is not easy to enter the dormant state. The process of stereoselective polymerization of butadiene and isoprene was carried out on the catalytic oxidation, butadiene and isoprene stereoselective polymerization of the metal complex containing different ligands. The results show that the insertion process of cis-1,4-monomer is better than that of trans-1,4-monomer in the process of polymerization. There is a large repulsive interaction between the ligand and the monomer in the whole-homopolymerization process, which is the main reason which leads to the more difficult to occur between the ligand and the monomer. in that proces of butadiene polymerization, the selectivity of cis-1,4 is mainly due to the strong interaction between the monomer in the corresponding transition state and the metal center; in contrast, the isoprene 1, 4 is inserted into the transition state, so as to facilitate the 3,4-selective polymerization of the isoprene. The mechanism of trans-1,4-polymerization of isoprene catalyzed by cationic Al-Al bimetallic complexes was studied. The results show that in three 'Possible active species[(C5Me5) La (. mu. 2-Me) 3AlMe] + (A).[(C5Me5) La (... 2-Me) 2AlMe2] + (B) and[(C5Me5) La (Me) (... 2-Me) AlMe2] + (C), it was found that species C may be a real active species that catalyzes the synthesis of trans-1,4-polyisoprene by exploring the process of chain initiation, the conversion of three species, and the separation of olefins to counter anions. It is found that the latter path is a more favorable polymerization process by the co-catalysis of the double-metal center of the Al-Al and the catalytic polymerization path of the single-center of the metal. in that proces of the catalytic polymerization of the single-metal center, AlMe3 is coordinated by a methyl group and a metal contact center as the ligand; in the polymerization system with the metal base as the center, the AlMe ligand tends to be far away from the metal contact center in the polymerization process so as to obtain the cis-1,4-polyisoprene, In agreement with the experimental results, the difference in the polymerization selectivity of the metal-and-metal-catalyzed system is mainly due to the fact that the metal-to-metal ratio is smaller than that of the metal, and the AlMe is easily dissociated from the metal center in the thermodynamics. The results show that the selectivity of the alkyl aluminum to the polymerization system plays a very important role.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O631.5
，
本文编号：2360711
[Abstract]:The development of high-performance olefin polymerization catalyst has become the main driving force for the development of a new type of polyolefin material. In recent years, cationic rare-earth metal complexes show a unique catalytic performance in the polymerization of olefins, which are of great concern to the researchers at home and abroad. However, the existing experimental means is difficult to detect and separate the active species of the relevant catalytic process, which is an obstacle to the discussion of the basic chemical problems such as the polymerization mechanism. By using the theory, the reaction mechanism can be studied from the molecular level, and the development of the new type of polyolefin catalyst and the new type of polymeric material is promoted to a great extent. In this paper, the reaction mechanism of a series of rare-earth metal complexes to catalyze the polymerization of olefins, including the effects of metals and auxiliary ligands, on the polymerization activity and the molecular mechanism of selective molecular mechanism, is discussed from the molecular level by using the QM (Quantum Mechanics) and the ONIOM calculation method. The main results are as follows: 1. The polymerization of 1-hexene with the cation-type rare-earth metal alkyl complex containing the C3-symmetric iPr-trisox ligand was studied. The results show that there is a large mutual exclusion between the auxiliary ligand and the (CH2) 3CH3 chain of 1-hexene in the transition state of the chain initiation and the chain growth. The whole-homopolymerization of 1-hexene is mainly the kinetic control process, followed by the chain end control mechanism, and the polymerization process catalyzed by the divalent cation active species is better than the one-valent species in the dynamics and thermodynamics, and the calculation results are consistent with the experimental results. the 1-hexene insertion process catalyzed by a metal-based species is more advantageous in kinetics than in the native species, and the cationic species is more easily generated than the corresponding species of the species, thus explaining the reason for the high activity of the cationic polymer complex. The regioselectivity and stereoselectivity of the cationic rare-earth metal complex[(H5-C5Me5) Ln (CH2SiMe3) (THF) n] + (A, Ln = Sc, Y, Lu, Gd, Sm; n = 0 (AL.), 1 (thfALn)),[(H5-C5Me5) Sc (CH2C6H4NMe2-0)] + (B) and[(-5-C5Me5) Sc (C6H4OMe-0)] + (C) in the catalytic styrene polymerization process, The effect of the internal and external sources of Lewis base on the microstructure of the chain end and the catalytic activity of different metals were studied. The results show that the exogenous Lewis base THF does not affect the selectivity of the polystyrene, but can reduce the polymerization activity; the amino-base endogenous Lewis base can reduce the regioselectivity of the chain initiation process, has no obvious effect on the stereoselectivity of the chain growth, The strong interaction between the metal atom and the oxygen atom tends to result in a fully-identical chain-end microstructure. The reason for the first time that the metal complex has higher activity is that it has a strong Lewis acidity, a smaller ionic radius, and the polymerization process is not easy to enter the dormant state. The process of stereoselective polymerization of butadiene and isoprene was carried out on the catalytic oxidation, butadiene and isoprene stereoselective polymerization of the metal complex containing different ligands. The results show that the insertion process of cis-1,4-monomer is better than that of trans-1,4-monomer in the process of polymerization. There is a large repulsive interaction between the ligand and the monomer in the whole-homopolymerization process, which is the main reason which leads to the more difficult to occur between the ligand and the monomer. in that proces of butadiene polymerization, the selectivity of cis-1,4 is mainly due to the strong interaction between the monomer in the corresponding transition state and the metal center; in contrast, the isoprene 1, 4 is inserted into the transition state, so as to facilitate the 3,4-selective polymerization of the isoprene. The mechanism of trans-1,4-polymerization of isoprene catalyzed by cationic Al-Al bimetallic complexes was studied. The results show that in three 'Possible active species[(C5Me5) La (. mu. 2-Me) 3AlMe] + (A).[(C5Me5) La (... 2-Me) 2AlMe2] + (B) and[(C5Me5) La (Me) (... 2-Me) AlMe2] + (C), it was found that species C may be a real active species that catalyzes the synthesis of trans-1,4-polyisoprene by exploring the process of chain initiation, the conversion of three species, and the separation of olefins to counter anions. It is found that the latter path is a more favorable polymerization process by the co-catalysis of the double-metal center of the Al-Al and the catalytic polymerization path of the single-center of the metal. in that proces of the catalytic polymerization of the single-metal center, AlMe3 is coordinated by a methyl group and a metal contact center as the ligand; in the polymerization system with the metal base as the center, the AlMe ligand tends to be far away from the metal contact center in the polymerization process so as to obtain the cis-1,4-polyisoprene, In agreement with the experimental results, the difference in the polymerization selectivity of the metal-and-metal-catalyzed system is mainly due to the fact that the metal-to-metal ratio is smaller than that of the metal, and the AlMe is easily dissociated from the metal center in the thermodynamics. The results show that the selectivity of the alkyl aluminum to the polymerization system plays a very important role.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O631.5
，
本文编号：2360711
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