XPS investigation of the electronic environment in selected heterogenized zirconocene catalysts

Abstract

Ethylbisindenyl zirconium dichloride (Et(Ind) 2 ZrCl 2 ) and the MAO methylalumoxane (MAO) co-catalyst were heterogenized on Davision silica 955 partially dehydroxylated at 275°C, following the concept of equilibrium adsorption. The influence of MAO on the electronic environment resulting from the heterogenization was investigated using XPS. Heterogenization of Et(Ind) 2 ZrCl 2 and MAO on the above silica generated two types of zirconocenium cations (Cation 1 and Cation 2), independent of the heterogenization methods. Based on the postulated surface chemistry, Cation 1 is presumed to be in the form of an ion-pair [SiO] − [Et(Ind) 2 ZrCl] Y , whereas Cation 2 is presumed to be a trapped multi-coordinated crown complex of MAO. In the absence of MAO, only Cation 1 is formed. The present study provides some support for the postulated surface chemistry regarding heterogenization of Et(Ind) 2 ZrCl 2 and MAO on silica.