文献类型：期刊文献

英文题名：Cr/PCCP-catalysed selective ethylene oligomerization: analysis of various conformations and the hemilabile methoxy group

作者：Zhong, Xuqin[1];Liu, Lin[1];Guo, Xing[1];Sun, Li[1];Liu, Boping[2];Liu, Zhen[1]

机构：[1]East China Univ Sci & Technol, Sch Chem Engn, Shanghai 200237, Peoples R China;[2]South China Agr Univ, Coll Mat & Energy, Guangzhou 510642, Peoples R China

年份：2022

卷号：12

期号：18

起止页码：5586

外文期刊名：CATALYSIS SCIENCE & TECHNOLOGY

收录：;EI(收录号：20223212554248);WOS:【SCI-EXPANDED(收录号:WOS:000835360200001)】；

基金：We thank the National Natural Science Foundation of China (22171084). The authors thank the Shanghai Pujiang Program (18PJ1402500), and the Open Project of State Key Laboratory of Chemical Engineering (SKL-ChE-18C01) at the East China University of Science and Technology for financial support. We acknowledge the East China University of Science and Technology for the supercomputer and generous computing resources.

语种：英文

外文关键词：Catalyst selectivity - Density functional theory - Design for testability - Expansion - Ligands - Molecules - Oligomerization - Oligomers

摘要：In this work, the effects of the hemilabile methoxy group in Cr-based catalysts bearing (C6H5)(2)-P(CH2)(2)P-(C6H5)(2) (PCCP) and (o-MeOC6H4)(C6H5)-P(CH2)(2)P-(C6H5)(o-MeOC6H4) (PCCPOMe) ligands on ethylene tri- and tetramerization were systematically investigated by density functional theory (DFT) calculations. Through analysis of the ensemble of low energy conformers of the intermediates and the transition states, the key geometrical features are of great importance to understand the switch between ethylene trimerization and tetramerization induced by the hemilabile methoxy group. Given the fact that the migratory insertion of the coordinated ethylene molecule occurs outside the metallacycle, the energy barrier tends to increase for insertion of the fourth ethylene molecule in the presence of the methoxy group. However, the one-step beta-H transfer takes place inside the metallacycle, and therefore it is less effected by introducing the methoxy group in the PCCP ligand. Starting from chromacycloheptane, the catalyst model A (Cr/PCCP) favours the migratory insertion of the fourth ethylene molecule resulting in the formation of 1-octene (14.9 kcal mol(-1) for expansion of chromacycloheptane vs. 16.3 kcal mol(-1) for decomposition of chromacycloheptane), while the catalyst model B (Cr/PCCPOMe) results in the formation of 1-hexene through reductive elimination by 3,7 H-shift in chromacycloheptane (17.6 kcal mol(-1) for expansion of chromacycloheptane vs. 16.1 kcal mol(-1) for decomposition of chromacycloheptane). The hemilability of the methoxy group in the PCCP ligand is of crucial importance in tuning the selectivity of ethylene tri-/tetramerization, which could shed some light on the design of new catalysts for ethylene selective oligomerization.