A highly active anilinotropone-based neutral nickel(II) catalyst for ethylene polymerization

The synthesis of a neutral nickel(II) complex of 2-(2,6-diisopropylanilino)tropone is described. The important attributes of this ligand include a hindered N-aryl ring, a five-membered-ring chelate, and an anionic N-donor. The complex has been characterized in the solid state by X-ray crystallography, and relevant features are discussed. The nickel complex is capable of polymerizing ethylene with a turnover frequency of up to 8.8 x 10(6) g of PE (mol of catalyst)(-1) h(-1) and of producing polyethylenes with a wide range of branching numbers by changes in pressure and temperature. The catalyst shows an excellent tolerance for polar additives in ethylene polymerization experiments and is quite insensitive to added PPh(3).(1)