The origin of living polymerization with an o-fluorinated catalyst: NMR spectroscopic characterization of chain-carrying species.

Autor: Möller HM; University of Konstanz, Department of Chemistry, Universitätstr. 10,D-78457 Konstanz, Germany. heiko.moeller@uni-konstanz.de, Baier MC, Mecking S, Talsi EP, Bryliakov KP
Jazyk: angličtina
Zdroj: Chemistry (Weinheim an der Bergstrasse, Germany) [Chemistry] 2012 Jan 16; Vol. 18 (3), pp. 848-56. Date of Electronic Publication: 2011 Dec 13.
DOI: 10.1002/chem.201102408
Abstrakt: To characterize the origin of living polymerization with nonmetallocene titanium-based catalysts containing o-fluoroaryl substituents, ethene polymerization by an o-fluorinated bis(enolatoimine) titanium catalyst and its nonfluorinated counterpart has been studied by multinuclear NMR spectroscopy by using methylaluminoxane (MAO) or AlMe(3)/CPh(3)B(C(6)F(5))(4) as activators. Formation of ion pairs of the type [TiL(2)Me][MeMAO] and [TiL(2)Me][B(C(6)F(5))(4)] has been observed for both catalysts. These ion pairs react with ethene to afford the chain-propagating species [TiL(2)P][MeMAO] and [TiL(2)P][B(C(6)F(5))(4)], respectively (P = growing polymeryl chain). For the o-F-substituted catalyst species of the second type, NMR spectroscopy provides evidence that the o-F substituents interact with the metal center. This interaction is proposed to keep the polymerization catalysis living by suppressing chain transfer to AlMe(3) and β-hydrogen transfer processes.
(Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
Databáze: MEDLINE
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