Synthesis, characterization and ethylene oligomerization of nickel complexes bearing N-(2-(1H-benzo[d]imidazol-2-yl)quinolin-8-yl)benzamide derivatives

A series of N-(2-(1-R-1H-benzo[d]imidazol-2-yl)quinolin-8-yl)-2-R(1)-4-R(2)-benzamide derivatives (5-12) was synthesized and characterized. These compounds 5-11 (5: R = H, R(1) = H, R(2) = H; : R = H, R(1) = Cl, R(2) = H; :R = H, R(1) = H, R(2) = Cl; : R = H, R(1) = H, R(2) = Br; : R = Me, R(1) = H, R(2) = H; 10: R = Et, R(1) = H, R(2) = H; : R = (i)Pr, R(1) = H, R(2) = H.) were treated with KOH, and then reacted with Ni(Ac)(2).4H(2)O to form their nickel complexes (-), however, the dimethylated compound reacted with NiCl(2).6H(2)O to give complex 14a. Further investigation confirmed that compound hydrolysized into a new compound N-methyl-2-(1-methyl-1H-benzo[d]imidazol-2-yl)quinolin-8-amine 14, and alternative synthesis confirmed the formation mechanism of 14a. All nickel complexes were characterized by elemental and spectroscopic analyses, and molecular structures of the representative compounds (12, 5a and 14a ) were determined by the single-crystal X-ray diffraction. These Ni(ii) complexes exhibited good to high activities up to 7.6 x 10(6)g mol(-1)(Ni) h(-1) in ethylene oligomerization upon activation with Et(2)AlCl. The reaction conditions and the nature of ligands affected on the catalytic performances of nickel complexes.