XPS investigation of the electronic environment in selected heterogenized zirconocene catalysts

Ethylbisindenyl zirconium dichloride (Et(Ind)(2)ZrCl2) and the MAO methylal umoxane (MAO) co-catalyst were heterogenized on Davision silica 955 partial ly dehydroxylated at 275 degrees C, following the concept of equilibrium ad sorption. The influence of MAO on the electronic environment resulting from the heterogenization was investigated using XPS, Heterogenization of Et(In d)(2)ZrCl2 and MAO on the above silica generated two types of zirconocenium cations (Cation 1 and Cation 2), independent of the heterogenization metho ds. Based on the postulated surface chemistry, Cation 1 is presumed to be i n the form of an ion-pair [SiO](-)[Et(Ind)(2)ZrCl](+), whereas Cation 2 is presumed to be a trapped multi-coordinated crown complex of MAO, In the abs ence of MAO, only Cation 1 is formed, The present study provides some suppo rt for the postulated surface chemistry regarding heterogenization of Et(In d)(2)ZrCl2 and MAO on silica, Copyright (C) 1999 John Wiley & Sons, Ltd.