Elucidation of Substituent Effects in the Polymerization of Propylene Promoted by Titanium Amidinates

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• 作者：Sinai Aharonovich ; Mark Botoshansky ; Yael S. Balazs ; Moris S. Eisen
• 刊名：Organometallics
• 出版年：2012
• 出版时间：April 23, 2012
• 年：2012
• 卷：31
• 期：8
• 页码：3435-3438
• 全文大小：277K
• 年卷期：v.31,no.8(April 23, 2012)
• ISSN：1520-6041

文摘

In polymerization reactions, the molecular weight of the polymer depends on the rates of monomer insertion, chain termination, and chain transfer. Here we do present studies indicating why chelating octahedral benzamidinate group IV complexes, which promote the polymerization of propylene with MAO, exhibit a linear free energy relationship with the steric Taft parameter. We correlate that this relationship is encountered with the para substituent of the aromatic ring, far away from the active catalytic site. A number of known events are put together to shed light on the effect of the ancillary ligands in the catalytic polymerization, and a new plausible mechanism for the process is presented.