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

A general synthetic route for the preparation of 2-anilinoperinaphthenones is reported. 2-(2,6-Dimethylanilino)perinaphthenone (4a) and 2-(2,6-diisopropylanilino)perinaphthenone (4b) are used as ligands for the corresponding neutral nickel(II) complexes [[(2,6-Me(2)C(6)H(3))-NC(13)H(7)O]Ni(Ph)(PPh(3))] (5a) and [[(2,6-(i)Pr(2)C(6)H(3))NC(13)H(7)O]Ni(Ph)(PPh(3))] (5b). The key features of these nickel complexes are a hindered N-aryl ring, a five-membered-ring nickel chelate, and an anionic N-donor moiety. Complexes 5a,b are active, but short-lived, ethylene polymerization catalysts with turnover numbers in excess of 60 000 mol ethylene/mol catalyst. Polymer branching is controlled by variation of temperature and pressure. A correlation between ethylene pressure and polymer molecular weight suggests that chain transfer occurs by a beta-hydride elimination pathway. Finally, decomposition of 5b to free ligand is observed under the polymerization conditions employed.