Dichlorocobalt(II) Complexes Ligated by Bidentate 8-(Benzoimidazol-2-yl)quinolines: Synthesis, Characterization, and Catalytic Behavior toward Ethylene

Abstract

A series of (8-(benzoimidazol-2-yl)quinoline)dichlorocobalt(II) complexes was prepared and characterized, and single-crystal X-ray diffraction revealed the distorted-tetrahedral geometry around the cobalt atom. Activated with methylaluminoxane (MAO), these cobaltous complexes showed special properties of ethylene reactivity: ethylene oligomerization with an observed activity up to 3 × 104 g (mol of Co)−1 h–1 atm–1 with reaction temperature lower than 60 °C at ambient or 10 atm ethylene pressure and ethylene polymerization with an observed activity up to 1 × 105 g (mol of Co)−1 h–1 atm–1 with reaction temperature higher than 60 °C at 30 atm ethylene pressure, indicating two potentially active species formed at different reaction parameters. The obtained polyethylenes with high molecular weights and narrow molecular weight distributions, to the best of our knowledge, give the first proof of dichlorocobalt complex precatalysts bearing bidentate ligands acting as single-site catalysts in ethylene polymerization.