文献类型：期刊文献

英文题名：Mechanistic Studies on the Switching from Ethylene Polymerization to Nonselective Oligomerization over the Triphenylsiloxy Chromium(II)/Methylaluminoxane Catalyst

作者：Zhang, Jialong[1];Qiu, Pengyuan[1,2];Liu, Zhen[1];Liu, Boping[1];Batrice, Rami J.[3];Botoshansky, Mark[3];Eisen, Moris S.[3]

机构：[1]E China Univ Sci & Technol, State Key Lab Chem Engn, Shanghai 200237, Peoples R China;[2]SINOPEC, Shanghai Res Inst Petrochem Technol, Shanghai 201208, Peoples R China;[3]Technion Israel Inst Technol, Schulich Fac Chem, IL-32000 Haifa, Israel

年份：2015

卷号：5

期号：6

起止页码：3562

外文期刊名：ACS CATALYSIS

收录：;EI(收录号：20152400930350);WOS:【SCI-EXPANDED(收录号:WOS:000355964300043)】；

基金：National Natural Science Foundation of China (No. 20774025) and Key Projects in the National Science & Technology Pillar Program during the 11th Five-Year Plan Period (2007BAE50B04) are thanked for financial support. This work is also financially supported by the Research Program of the State Key Laboratory of Chemical Engineering, the Program of Introducing Talents of Discipline to Universities (B08021), and the Fundamental Research Funds for the Central Universities. Dr. P. Zhao (Institute of Fine Chemicals, East China University of Science and Technology) and Dr. I. Barzilai (Faculty of Chemistry, Technion-Israel Institute of Technology) are thanked for FT-IR and GC measurements, respectively.

语种：英文

外文关键词：Phillips catalyst; ethylene polymerization; ethylene nonselective oligomerization; active species; switching mechanism; DFT calculations

摘要：Our previous experimental report showed a switching behavior from ethylene polymerization to nonselective oligomerization by a novel triphenylsiloxy complex of chromium(II) [(Ph3SiO)Cr center dot(THF)](2)(mu-OSiPh3)(2) (1) together with methylaluminoxane (MAO) as a cocatalyst. In this work, combined experimental and computational studies were carried out to shed some light on the nature of the active species and their fascinating switching mechanism. The experimental results and DFT calculations suggested that (i) the chain propagation and chain transfer processes proceed via a Cossee-Arlman mechanism and beta-hydrogen transfer to the chromium center, respectively; (ii) the trivalent cationic model [(Ph3SiO)(CrMe)-Me-III](+) and [(eta(6)-toluene)(CrMe2)-Me-III](+) which could be generated by a disproportionation reaction, are the most plausible active species for ethylene polymerization) and the divalent cationic model [(eta(6)-toluene)(CrMe)-Me-II](+) night be responsible for ethylene nonselective oligomerization. A switching mechanism from ethylene polymerization to nonselective oligomerization in the 1/MAO catalyst system was proposed on the basis of DFT calculations These results may have useful implications for studying active species and the mechanism of transition-metal-catalyzed olefin polymerization and oligomerization.