title: The origin of living polymerization with an o-fluorinated catalyst: NMR spectroscopic characterization of chain-carrying species.
abstract: 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.
authors.affiliation: University of Konstanz, Department of Chemistry, Universitätstr. 10,D-78457 Konstanz, Germany. heiko.moeller@uni-konstanz.de
authors.forename: Heiko M
authors.initials: HM
authors.lastname: Möller
authors.forename: Moritz C
authors.initials: MC
authors.lastname: Baier
authors.forename: Stefan
authors.initials: S
authors.lastname: Mecking
authors.forename: Evgenii P
authors.initials: EP
authors.lastname: Talsi
authors.forename: Konstantin P
authors.initials: KP
authors.lastname: Bryliakov