Ferrous and Cobaltous Chlorides Bearing 2,8-Bis(imino)quinolines: Highly Active Catalysts for Ethylene Polymerization at High Temperature

A series of 2,8-bis(1-aryliminoethyl)quinolines [2,8-(2,6-R 1 2 -4-R 2 C 6 H 2 N═CCH 3 ) 2 C 9 H 5 N ( L ), R 1 = Me, Et, or i- Pr, R 2 = H or Me] is synthesized and used in the reaction with ferrous or cobaltous chlorides. The corresponding complexes L MCl 2 are limitedly formed with ligands containing ortho -methyl groups of the imino phenyl rings (R = H, M = Fe ( Fe1 ), M = Co ( Co1 ); R = Me, M = Fe ( Fe2 ), M = Co ( Co2 ). The X-ray diffraction study reveals a distorted pyramidal geometry of Co1 around the cobalt atom. These complexes, activated with methylaluminoxane (MAO), show unique properties toward ethylene polymerization: no activity observed at low temperature, but high activity achieved at temperatures higher than 80 °C (up to 7.61 × 10 6 g·mol −1 ·h −1 at 100 °C). Moreover, the polyethylenes obtained are high molecular weight with narrow molecular distribution. This is the first example of iron and cobalt procatalysts with high activity for ethylene polymerization at high temperature.