Structures and styrene polymerization activities of a series of nickel complexes bearing ligands of pyrazolone derivatives

A series of nickel complexes with β-ketoamine ligands based on pyrazolone derivatives were synthesized by condensing pyrazolone with aniline, 2-chloroaniline or naphthylamine and then reacting the produced β-ketoamine with nickel halide. The solid-state structures of these three complexes were determined by single-crystal X-ray diffraction. The bis(β-ketoamine)nickel complexes are all air-stable and can act as highly active catalyst precursors for styrene polymerization with activation of methylaluminoxane under mild reaction conditions. The activity of the catalyst for styrene polymerization is as high as 2.10 × 105 g polymer/mol Ni h. Both steric and electronic effects were found to be important and influential for catalytic activity. Copyright © 2005 John Wiley & Sons, Ltd.