Vinyl polymerization of norbornene catalyzed by a series of bis(β-ketoiminato)nickel (II) complexes in the presence of methylaluminoxane

A series of nickel complexes with β-ketoiminato ligands based on pyrazolone derivative were synthesized and characterized, which are highly active catalyst precursors for norbornene polymerization under mild reaction conditions through a vinyl-type polymerization mechanism. The catalytic activity could be up to 3.38 × 107 g polymer/mol Ni h. The molecular weight distributions of the polynorbornenes (Mw/Mn = 2.05–2.56) indicate the presence of a single active species in the polymerization process.