Selectivity Effects on N,N,N′‑Cobalt Catalyzed Ethylene Dimerization/Trimerization Dictated through Choice of Aluminoxane Cocatalyst

The cobalt­(II) chloride complexes, [2-(C7H4­N2H)-8-(ArN)­C10H8­N]­CoCl2 (Ar = 2,6-Me2­C6H3 Co1; 2,6-Et2­C6H3 Co2; 2,6-i-Pr2­C6H3 Co3; 2,4,6-Me3­C6H2 Co4; 2,6-Et2-4-Me­C6H2 Co5; 2,4,6-t-Bu3­C6H2 Co6), have each been prepared by a one-pot template reaction of 2-benzoimidazolyl-5,6,7-trihydroquinolin-8-one with the corresponding aniline in the presence of cobalt dichloride. The molecular structures of the methanol adducts, Co1­(HOMe) and Co4­(HOMe), reveal distorted octahedral geometries that self-assemble to form networks based on NH···Cl and OH···Cl intermolecular hydrogen bonding interactions. On activation with methylaluminoxane (MAO), all six cobalt complexes catalyzed ethylene dimerization with a high selectivity for 1-butene. By marked contrast, with modified methylaluminoxane (MMAO), products the result of ethylene dimerization and trimerization were observed with a bias toward the C6 products (up to 49% 1-hexene). In general, the MMAO-promoted oligomerizations display higher catalytic activities with mesityl-containing Co4 the stand-out performer [7.60 × 105 g·mol–1(Co) h–1 at 50 °C].