文献类型：期刊文献

英文题名：Zirconium complexes with versatile β-diketiminate ligands: Synthesis, structure, and ethylene polymerization

作者：Gong, Shaogang[1];Ma, Haiyan[1];Huang, Jiling[1]

机构：[1]E China Univ Sci & Technol, Organomet Chem Lab, Shanghai 200237, Peoples R China

年份：2008

卷号：693

期号：23

起止页码：3509

外文期刊名：JOURNAL OF ORGANOMETALLIC CHEMISTRY

收录：;EI(收录号：20084111637408);WOS:【SCI-EXPANDED(收录号:WOS:000259890300007)】；

基金：This work is subsidized by the National Basic Research Program of China (2005CB623801), National Natural Science Foundation of China (NNSFC, 20604009, 20774027), the Program for New Century Excellent Talents in University (for H. Ma, NCET-06-0413), Shanghai Rising-Star Program (06QA14014) and the Scientific Research Foundation for the Returned Overseas Chinese Scholars (SRF for ROCS, SEM). All the financial supports are gratefully acknowledged. The authors also thank the very kind donation of a glove-box by the AvH foundation.

语种：英文

外文关键词：beta-Diketiminate; Zirconium; Polyethylene; Catalysis; Polymerization

摘要：A series of zirconium complexes (2c, 2d, 2f, 2g, 2h, 2i) containing symmetrical or unsymmetrical beta-diketiminate ligands were synthesized by the reaction of ZrCl4.2THF with lithium salt of the corresponding ligand in 1: 2 molar ratio. X-ray crystal structures reveal that complexes 2d and 2g adopt distorted octahedral geometry around the zirconium center. These complexes showed moderate activities for ethylene polymerization, when methylaluminoxane (MAO) was used as cocatalyst. The steric and electronic effects of the substituents at the phenyl rings had considerable influence on the catalytic activities of the metal complex, as well as the molecular weights and molecular weight distributions (MWD) of produced polymers. Introduction of electron-withdrawing CF3 group to phenyls in the ligand led to a significant increase of catalytic activities, and complex 2f (p-CF3) exhibited the highest catalytic activity of 7.45 x 10(5) g PE/mol-Zr . h among the investigated complexes. Complexes 2a-d could produce ultrahigh molecular weight polyethylenes (UHMWPE) that were hardly dissolvable in decahydronaphthalene or 1,2-dichlorobenzene under the molecular weight measurement conditions. Nevertheless, polyethylenes with broad MWD could be afforded by complexes 2g-i, which was probably due to the introduction of bulky unsymmetrical ligands leading to the formation of multi active species under polymerization conditions. High-temperature C-13 NMR data indicate the linear structure of obtained polyethylenes. (C) 2008 Elsevier B.V. All rights reserved.