Influence of the counterion MeB(C6F5)3- and solvent effects on ethylene polymerization catalyzed by [(CpSiMe2NR)TiMe]+: A combined density functional theory and molecular mechanism study
Influence of the counterion MeB(C6F5)3- and solvent effects on ethylene polymerization catalyzed by [(CpSiMe2NR)TiMe]+: A combined density functional theory and molecular mechanism study
复制标题
抗衡离子 MeB(C6F5)3- 和溶剂效应对 [(CpSiMe2NR)TiMe] 催化乙烯聚合的影响：密度泛函理论和分子机理的结合研究
DOI：
10.1021/om0341202
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发表时间：
2004
期刊：
影响因子：
2.8
通讯作者：
T. Ziegler
中科院分区：
文献类型：
--
作者：
Zhitao Xu;K. Vanka;T. Ziegler
采用结合密度泛函理论和分子机理（QM/MM）的方法研究了乙烯单体在（CpSiMe 2NtBu）（R）Ti-μ-MeB（C6 F5）3的Ti−R键上的第一次（R = Me）和第二次（R =丙基）插入.本文对CGC催化乙烯聚合反应的链增长过程进行了全面的理论研究。反溶剂效应和溶剂效应在乙烯第一次和第二次扩散过程中都起着重要作用，因此在机理研究中不可忽视。反离子和溶剂的影响不仅改变了反应势垒，而且改变了链增长的速率决定步骤，从插入到摄取。对于气相和溶液中的第二次乙烯增长，顺式方法优于反式方法。乙烯第一次增长的总反应势垒略高。
A combined density functional theory and molecular mechanism (QM/MM) method has been used to study the first (R = Me) and the second (R = propyl) insertion of the ethylene monomer into the Ti−R bond of (CpSiMe2NtBu)(R)Ti-μ-MeB(C6F5)3. The present extensive theoretical investigation provides a comprehensive analysis of the chain propagation process for ethylene polymerization catalyzed by CGC in the presence of the counterion MeB(C6F5)3-. Both the counterion and solvent effects play important roles in the first and second ethylene propagations and therefore cannot be ignored in the mechanistic study. The influence of the counterion and the solvent not only changes the reaction barriers but also alters the rate-determining step for the chain propagation, from insertion to uptake. The cis approach is preferred over the trans approach for the second ethylene propagation in the gas phase as well as in solution. The total reaction barrier for the first ethylene propagation has been calculated to be slightly hig...