CATALYTIC ACTIVITY OF SUPPORTED TUNGSTEN PHENOXIDE COMPLEXES IN OLEFIN METATHESIS - XPS CHARACTERIZATION - APPLICATION OF MOLECULAR MODELING TO SURFACE ORGANOMETALLIC CHEMISTRY

Heterogeneous catalysts with respect to the metathesis of olefins has been prepared by a controlled thermal reaction between W(O-2,6-C(6)H(3 )X(2))(2)Cl-4 (X = t-Bu, Me, Br, and Cl) or W(MBPD)Cl-4 and a silica s upport. Surface characteristics of the powder catalysts and a model ca talyst have been determined by conventional XPS and Angle-Resolved XPS (AR-XPS). The catalytic activity has been related to the structure of the molecular entities on the surface of the precursor. Furthermore, a model for hydroxylated silica is described. The surface structure (= SiO)(2)W(O-2,6-C(6)H(3)X(2))(2)Cl-2 is modeled to determine the prefer red arrangement of the tungsten diphenoxide species on the hydroxylate d support.