Copolymerization of norbornene with ethylene catalyzed by nickel complexes with phosphorylide ligands

Catalytic systems based on salts or complexes of nickel in combination with alkylaluminum chlorides that were previously used for the homopolymerization of norbornene were shown to be incapable of producing norbornene copolymers with ethylene or conjugated dienes due to the efficient chain-transfer reaction. It was found that the copolymerization of norbornene with ethylene proceeds under mild conditions when nickel complexes containing chelating phosphorylide ligands, nickel-phenyl bonds, and auxiliary weakly bonded ligands (pyridine or norbornene itself) are used. No cocatalysts are required for manifestation of the catalytic activity of these complexes. The ratio of norbornene and ethylene units in high-molecular-mass copolymers is close to equimolar. The feasible scheme of copolymerization is discussed.