A series of 1,2-bis(arylimino)acenaphthylidenes (L1-L5) and their corresponding 4,4'-methylenebis(1-(2,6-diisopropylphenylimino)-2-(arylimino)acenaphthylene) derivatives (L6-L10) were synthesized and used to form mono-nuclear nickel bromides LnNiBr2 (n = 1-5, Ni1-Ni5) and bi-nuclear nickel halides LnNi2X4 (n = 6-10: X = Br, Ni2-1-Ni2-5; n = 4, X = Cl, Ni2-6). All the organic compounds were fully characterized by FT-IR spectra, NMR measurements and elemental analysis. The nickel complexes were characterized by FT-IR spectra and elemental analysis and the molecular structures of the representative complexes Ni1, Ni2-1 and Ni2-3 were confirmed by single-crystal X-ray diffraction. Upon activation with either Et2AlCl or MAO, all the nickel complex pre-catalysts exhibited high activity toward ethylene polymerization over the temperature range from ambient to 50 °C. In general, the bi-nuclear complexes showed a positive synergetic effect with higher activity than their mono nuclear analogs. The resultant polyethylene possessed higher molecular weight and a high degree of branching.

A series of nickel(II) dihalides complexes bearing 4,5-bis(arylimino)pyrenylidenes, NiX2(2,6-R(1)-4-R(2)C6H2N)2C16H8, was synthesized and characterized by FT-IR spectroscopy, elemental analysis, and single crystal X-ray diffraction for the organic compounds (L2 and L3) and the nickel complexes (C1 and C2). The molecular structures of C1 (R(1) = Me, R(2) = H, X = Br) and C2 (R(1) = R(2) = Me, X = Br) revealed a distorted tetrahedral geometry around the nickel centre. Upon treatment with the co-catalysts MAO, EASC and MMAO, all the nickel pre-catalysts exhibited high activities (of up to 4.42 × 10(6) g(PE) mol(Ni)(-1) h(-1)) for ethylene polymerization, and produced polyethylene products with a high degree of branching (up to 130 branched per 1000 carbons) and narrow molecular weight distribution. The influence of the reaction parameters and the nature of the ligands on the catalytic behavior of the title nickel complexes have been investigated.