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 hin dered N-aryl ring, a five-membered-ring chelate, and an anionic N-donor. Th e complex has been characterized in the solid state by X-ray crystallograph y, and relevant features are discussed. The nickel complex is capable of po lymerizing 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 rang e of branching numbers by changes in pressure and temperature. The catalyst shows an excellent tolerance for polar additives in ethylene polymerizatio n experiments and is quite insensitive to added PPh3.(1)