桥联茂钛配合物催化丙烯聚合反应选择性的理论研究

发布时间：2018-08-27 11:57

【摘要】：采用密度泛函方法对3种不同类型的硅桥联茂钛配合物[Me_2SiN(Me_4Cp)TiCl_2(A),Me_2SiCpFluTiCl_2(B)及Me_2SiInd_2TiCl_2(C)]催化丙烯聚合反应的选择性进行了理论研究.计算结果表明,硅桥联茂金属配体的空间结构是其催化烯烃聚合反应的区域选择性和立体选择性的主要原因.聚合过程中,α-烯烃配位有1,2插入(一级插入)和2,1插入(二级插入)2种方式,3种硅桥联茂金属催化剂均表现为烯烃的一级插入,这种区域选择性与催化剂硅桥联配体的刚性结构密切相关.对烯烃聚合反应链增长机理进行了理论计算,结果表明,具有Cs对称性的Me_2SiN(Me_4Cp)TiCl_2和Me_2SiCpFluTiCl_2催化丙烯聚合分别得到无规立构和间规立构的聚烯烃产物,而具有C_2对称性的Me_2SiInd_2TiCl_2催化丙烯聚合得到等规立构的聚烯烃产物,与实验结果一致.
[Abstract]:The selectivity of three kinds of silicon-bridged titanocene complexes [Me_2SiN (Me_4Cp) TiCl_2 (A) (M _ 2SiCpFluTiCl _ 2 (B) and Me_2SiInd_2TiCl_2 (C)] to propylene polymerization was studied by density functional method. The results show that the spatial structure of silicon-bridged metallocene ligands is the main reason for the regioselectivity and stereoselectivity of olefin polymerization. In the process of polymerization, there are two types of 伪 -olefin coordination insertion: 1 ~ 2 insertion (first insertion) and 2 ~ (-1) insertion (second order insertion). Three kinds of silicon bridged metallocene catalysts all exhibit first-order insertion of olefin. This regioselectivity is closely related to the rigid structure of the silicon-bridged ligand over the catalyst. The chain growth mechanism of olefin polymerization was calculated theoretically. The results showed that Me_2SiN (Me_4Cp) TiCl_2 with Cs symmetry and Me_2SiCpFluTiCl_2 catalyzed propylene polymerization were used to obtain polyolefin products with random and syndiotactic structure, respectively. The isotactic polyolefin products obtained by propylene polymerization catalyzed by Me_2SiInd_2TiCl_2 with C _ S _ 2 symmetry are in good agreement with the experimental results.
【作者单位】：北京服装学院材料科学与工程学院;北京化工大学理学院化工资源有效利用国家重点实验室;
【基金】：北京服装学院重点科研项目(批准号:2014A-01)资助~~
【分类号】：O631.5

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