Drastic ligand electronic effect on anilido–imino nickel catalysts toward ethylene polymerization

A novel nitro–anilido–imino nickel complex (Ar1NCHC6H3(-5-NO2)NAr2)NiBr (Ar1 = Ar2 = 2,6-dimethylphenyl) was designed, synthesized, and characterized to investigate ligand electronic effect on late transition metal olefin polymerization catalysts. As a catalyst for ethylene polymerization, neutral anilido–imino nickel complex with an electron-withdrawing nitro group showed good activity (442.1 kg (mol Ni h)−1) with MAO as cocatalyst. The catalytic activity and molecular weight of the obtained products were significantly affected by electronic effect of the anilido–imine ligand. Theoretical calculations suggested that ligand electronic effect led to different charge distribution on the nickel metal atom, and the catalytic activity predominantly increased with an increase in electrophilicity of the nickel metal center.