Theoretical study of ethylene polymerization on Ziegler–Natta catalysts and on metallocene catalysts
Theoretical study of ethylene polymerization on Ziegler–Natta catalysts and on metallocene catalysts
复制标题
齐格勒-纳塔催化剂和茂金属催化剂上乙烯聚合的理论研究
DOI：
10.1016/s1381-1169(99)00277-0
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发表时间：
1999
影响因子：
--
通讯作者：
A. Shiga
中科院分区：
文献类型：
--
作者：
A. Shiga
通过配对相互作用轨道（PIO）分析和LFO计算，研究了oh - d1ch3氯化锡簇/C2H4（Ziegler-Natta催化剂模型体系）和Td-d0，-d1CH3TiCp2/C2H4（茂金属催化剂模型体系）上乙烯的插入。从催化位点到乙烯的电子离域和从乙烯到催化位点的电子离域在乙烯插入过程中起着至关重要的作用。前者取决于活性位点的亲核性，后者取决于活性位点的亲电性。通过LFO计算对其进行定量估计。在Ohsystems的情况下，由于Cl阴离子位于反应平面上的乙烯上，因此催化剂的亲电性降低。在Td体系中，由于亲核性和亲电性很好地平衡了，亲核性和亲电性并没有因为没有乙烯的反式配体而减弱。oh - d1ti4簇可以作为ticl3晶体表面活性位点的合适模型。
Ethylene insertion on Oh-d1CH3Tinchloride clusters/C2H4(model systems of Ziegler–Natta catalysts) and Td-d0,-d1CH3TiCp2/C2H4(model systems of metallocene catalysts) were studied by using paired interacting orbitals (PIO) analysis and LFO calculation. Electron delocalization from catalytic site to ethylene and that from ethylene to catalytic site played a crucial role in ethylene insertion. The former depends on the nucleophilicity of the active site and the latter on the electrophilicity of the active site. They were quantitatively estimated by LFO calculation. In the case of Ohsystems, the electrophilicity of the catalyst decreased because of the Cl anion located trans to the ethylene in the reaction plane. In the case of Td systems, since the electrophilicity was not weakened because of the absence of the trans ligand to the ethylene, the nucleophilicity and electrophilicity were well balanced. The Oh-d1Ti4cluster could be a suitable model of the active site on the TiCl3crystalline surface.