On the Fate of Silica-Supported Half-Metallocene Cations: Elucidating a Catalyst’s Deactivation Pathways

Single-site silica-supported hemizirconocene ([(≡SiO)Zr(Cp*)Me 2 ] (Cp* = C 5 Me 5 ) was prepared by grafting the corresponding trimethyl derivative onto SiO 2-700 and fully characterized. Upon activation by B(C 6 F 5 ) 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(C 6 F 5 ) 3 ] and that deactivation proceeds mainly by [MeB(C 6 F 5 ) 3 ] − degradation via C 6 F 5 group transfer onto zirconium and, to a minor extent, through siloxane bridge opening by Zr–Me.