Striking a Compromise: Polar Functional Group Tolerance versus Insertion Barrier Height for Olefin Polymerization Catalysts

The coordination–insertion random copolymerization of polar and nonpolar olefins holds great potential for the design of new polymers with targeted properties. However, examples of catalysts capable of such polymerization still remain scarce, the majority of which are based on Pd^II and some also on Ni^II. So far, the apparent superiority of Pd^II has not been rationalized. In this work, the catalytic potential of a broad range of transition metals is assessed by investigating their polar functional group tolerance and insertion barrier heights for realistic and comparable complexes. Multivariate regression models suggest that the π-back-donation ability of the metal plays an important role in both the polar functional group tolerance and the insertion barrier height. Specifically, the polar functional group tolerance and insertion barrier height were found to correlate positively, indicating that a compromise must be struck. Pd^II seems to strike this balance optimally, thus explaining its prominent position as a transition-metal catalyst for copolymerization of polar with nonpolar olefins.