Olefin polymerization at aluminum? A theoretical study

We have studied the balance between olefin insertion and beta -hydrogen tra nsfer to monomer for all "well-defined" aluminum polymerization catalysts r eported to date. Consistently, the balance is predicted to be significantly worse than for Me2AlEt, implying that none of the proposed active species, should give a high-molecular-mass polymer. A more systematic analysis of l igand effects allows a rationalization of these results and shows that smal l modifications to the proposed active species are unlikely to solve the pr oblem. We conclude that olefin polymerization at a single aluminum center i s, rather unlikely. Alternative interpretations of the experimental data ar e discussed.