Nickel complexes bearing 2-(1H-benzo[d]imidazol-2-yl)-N-benzylidenequinolin-8-amines: Synthesis, structure and catalytic ethylene oligomerization

A series of 2-(1H-benzo[d]imidazol-2-yl)-N-benzylidenequinolin-8-amines was synthesized and characterized. They are stable as solids while displaying a tendency to decompose in solution. On reaction with NiCl2, different coordination pattern sets of L·NiCl2 or [L2Ni]2+·2Cl− are obtainable in THF or ethanol. When activated by Et2AlCl, the complexes L·NiCl2 exhibit good to high catalytic activities and selectivities for 1-C4 in ethylene oligomerization, while the complexes [L2Ni]2+·2Cl− hardly showed any activity, which is attributable to nickel coordination by two ligands barring interaction of ethylene with the metal center.