Investigations into the Mechanism of Activation and Initiation of Ethylene Polymerization by Bis(imino)pyridine Cobalt Catalysts:  Synthesis, Structures, and Deuterium Labeling Studies

The activation of bis(imino)pyridine cobalt(II) precatalysts by MAO leads initially to a bis(imino)pyridine cobalt(I) cationic species with no cobalt−C(alkyl) bond into which insertion can occur. Mechanistic studies have shown that the initiation of polymerization from this species involves incorporation of alkyl groups from the cocatalyst, most likely involving attack of methide anion (from the counteranion) on a cobalt-ethylene species.