Mary Chan, Liqun Deng Tim Firman,,Peter.Margl, Artur Michalak, Rochus Schmid, Tom.K.Woo, Kumar Vanka, and Tom.Ziegler. Department of Chemistry University of Calgary, Calgary,Alberta,Canada T2N 1N4.
 

Cationic single site olefin polymerization catalysts have evolved beyond group-4 metallocenes. We discuss in the first part of the talk possible ground rules for the design of catalysts with d⁰-metals and ligands other than cyclopentadienyls. The second part will cover catalysts of early transition metals with a few d-electrons. It will be shown that adding a few d-electrons changes the ligand requirements considerably. The final part discusses catalysts of late transition metals and their ability to make branched polymers as well as polymers containing polar monomers. Attention will also be given to the role of the solvent and the counter-anion, with special emphasis on the possible structures of the anion [MeMAO]^- (MAO: methylalumoxane). Our study is based on density functional theory (DFT) as well as valence bond considerations. We shall finally discuss the possibility of designing neutral catalysts for which activators are not required.