On the Fate of Silica-Supported Half-Metallocene Cations: Elucidating a Catalyst’s Deactivation Pathways
作者:Nicolas Popoff、Régis M. Gauvin、Aimery De Mallmann、Mostafa Taoufik
DOI:10.1021/om3003224
日期:2012.7.9
Single-site silica-supported hemizirconocene ([( SiO)Zr(Cp*)Me-2] (Cp* = C5Me5) was prepared by grafting the corresponding trimethyl derivative onto SiO2-700 and fully characterized. Upon activation by B(C6F5)(3) the system catalyzes ethylene polymerization but quickly deactivates. From combined spectroscopic and analytical studies, it is shown that methyl abstraction first affords the expected supported ion pair [( SiO)Zr(Cp*)Me][MeB(C6F5)(3)] and that deactivation proceeds mainly by [MeB(C6F5)(3)](-) degradation via C6F5 group transfer onto zirconium and, to a minor extent, through siloxane bridge opening by Zr-Me.