文献类型：期刊文献

英文题名：Zirconium and hafnium complexes supported by linked bis(β-diketiminate) ligands: synthesis, characterization and catalytic application in 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：2009

期号：39

起止页码：8237

外文期刊名：DALTON TRANSACTIONS

收录：;EI(收录号：20094212376812);WOS:【SCI-EXPANDED(收录号:WOS:000270286000012)】；

基金：This work is subsidized by the National Basic Research Program of China (2005CB623801), National Natural Science Foundation of China (NNSFC, 20604009 and 20774027), the Program for New Century Excellent Talents in University (for H. Ma, NCET06-0413), Shanghai Rising-Star Program (06QA14014). All the financial supports are gratefully acknowledged. Authors also thank the very kind donation of a Braun glove-box by AvH foundation.

语种：英文

外文关键词：Hafnium compounds - Polymerization - Synthesis (chemical) - Ligands - Nuclear magnetic resonance spectroscopy - Molecular weight distribution - Chelation - Ethylene - Polyethylenes - Zirconium compounds

摘要：Zirconium and hafnium complexes bearing new 1,2-ethanediyl-or 1,3-propanediyl-linked bis(beta-diketiminate) ligands, [{CnH2n-(BDIAr)(2)}MCl2] (Ar = 2,6-Me-2-C6H3, 2,6-Cl-2-C6H3, 2,6-Pr-i(2)-C6H3; M = Zr, n = 2 (4a-c), n = 3 (5a-c); M = Hf, n = 2 (6b)), were synthesized via the reaction of MCl4 center dot 2THF and one equivalent of dilithium salt of the corresponding ligand. Distorted trigonal prismatic and octahedral coordination geometries as well as C-1-symmetric structures are found for zirconium complexes 4c and 5c in the solid state. Variable temperature H-1 NMR spectra indicated the fluxional nature of 4a and 5a in solution. Upon activation with methylaluminoxane (MAO), all these complexes except hafnium complex 6b displayed moderate catalytic activities for ethylene polymerization. 1,2-Ethanediyl-linked complexes 4a and 4b are generally more active than their 1,3-propanediyl-linked analogues. The substituents at the ortho-positions of the phenyl rings have different effect on the catalytic activities of 1,2-ethanediyl-linked series or 1,3-propanediyl-linked series. It is noteworthy that even at a low Al/Zr molar ratio of 500, the catalytic activities of these zirconium complexes could be retained. Polyethylenes with broad molecular weight distributions (MWD = 15.3-20.3) were produced, which might result from the. uxional character of the zirconium complexes. The linear structure of obtained polyethylenes was further determined by C-13 NMR spectroscopy and DSC analysis.