The Origin of Living Polymerization with an o-Fluorinated Catalyst: NMR Spectroscopic Characterization of Chain-Carrying Species
✍ Scribed by Prof. Dr. Heiko M. Möller; Moritz C. Baier; Prof. Dr. Stefan Mecking; Prof. Dr. Evgenii P. Talsi; Prof. Dr. Konstantin P. Bryliakov
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 586 KB
- Volume
- 18
- Category
- Article
- ISSN
- 0947-6539
No coin nor oath required. For personal study only.
✦ Synopsis
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.