Cationic Four- and Five-Coordinate Nickel(II) Complexes: Insights into the Nickel(II)-Catalyzed Copolymerization of Ethylene and Carbon Monoxide

Using the dppp-derived Ni(II) catalyst system 2, several four- and five-coordinate intermediates relevant to the alternating copolymerization of ethylene and carbon monoxide have been characterized. In addition, the activation barriers for the migratory insertion steps corresponding to chain growth have been determined to be at or below ca. 10 kcal/mol, indicating that a strongly stabilized catalyst resting state is most likely responsible for the low activity of 2 for copolymerization.