Mono- and di-nuclear nickel(II) complexes bearing 3-aryliminomethyl-2-hydroxybenzaldehydes: Synthesis, structures and vinyl polymerization of norbornene

A series of mono- and di-nuclear nickel(II) complexes bearing 3-aryliminomethyl-2-hydroxybenzaldehyde ligands were synthesized and characterized by FT-IR and elemental analysis along with single-crystal X-ray diffraction. The X-ray diffraction analysis revealed that the dinuclear nickel complexes formed with two bridged ligands and one bromide around each nickel center and the mononuclear nickel complexes bearing two centrosymmetrical ligands exhibited a distorted square-planar geometry. Upon activation with methylaluminoxane (MAO), all these nickel complexes displayed high catalytic activities up to 9.88 × 107 g(PNB) mol−1(Ni) h−1 (6b) for the vinyl polymerization of norbornene, yielding the vinyl-type PNBs with high molecular weights and narrow molecular weight distributions. The steric and electronic factors of ligands and reaction parameters had influences on the catalytic properties.