期刊
JOURNAL OF ORGANOMETALLIC CHEMISTRY
卷 693, 期 1, 页码 155-163出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jorganchem.2007.10.037
关键词
ab initio calculations; metallocenes; hafnium; activation; methylation
The influence of ligand structure of hafnocenes on activation of the polymerization catalysts has been studied by quantum chemical methods. Altogether 54 hafnocenes were included in the analysis, supplemented by four zirconocenes for comparison. The trends in structural and electronic parameters relevant in the catalyst activation step were studied for the dichloride, dimethyl and cationic monomethyl forms of the catalysts. The effects of ligand modifications were analyzed as functions of the metal, ancillary cyclopentadienyl-based ligand, ligand substituent and the ligand bridge, making comparisons to experimental data. Generally, large aromatic ligands together with electron donating ligand substituents stabilize the catalytically active species, thus facilitating the catalyst activation process. The obtained trends are expected to aid in the development of new high-performance polymerization catalysts. (c) 2007 Elsevier B.V. All rights reserved.
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