A series of iron(II) (7a-11a) and cobalt(II) (7b-11b) 2-(1-methyl-2-benzimidazolyl)-6-(1-(arylimino)ethyl)pyridyl complexes were synthesized, as well as bidentate iron(II) and cobalt(II) complexes ligated by 2-(2-benzimidazolyl)-6-methylpyridine, 2-(carboethoxyl)-6-(2-benzimidazolyl)pyridine, and 2-(1methyl-2-benzimidazolyl)-6-acetylpyridine. All organic compounds were fully characterized by NMR and IR spectroscopy and elemental analysis, while the metal complexes were carefully examined by IR spectroscopy and elemental analysis. Their molecular structures were determined by single-crystal X-ray diffraction analysis. The bidentate metal complexes display a distorted-tetrahedral coordination geometry; however, 2a is an exception, with a distorted-trigonal-bipyramidal geometry due to coordination of one DMF molecule. The X-ray crystallographic studies on all of the tridentate metal complexes revealed the coordination geometry as a distorted trigonal bipyramid. Upon activation with MAO or MMAO, the iron(II) 2-(2-benzimidazolyl)-6-(1-(arylimino)ethyl)pyridyl complexes showed high activities with good R-olefin selectivity, while the cobalt(II) analogues displayed moderate to good catalytic activities. However, other bidentate metal complexes showed considerable moderate catalytic activity. The oligomers and polyethylene waxes obtained were R-olefins, and the distribution of oligomers resembled Schulz-Flory rules with some exceptions. Various reaction parameters were investigated, and the results revealed that both the steric and electronic effects of ligands affect the catalytic activities of their metal complexes as well as the distribution of products.

A series of nickel complexes ligated by 2-(2-benzimidazole)-6-methylpyridine, 2-(1-methyl-2-benzimidazole)-6-acetylpyridine, and 2-(1-methyl-2-benzimidazole)-6-(1-aryliminoethyl)pyridine was synthesized and examined by IR spectroscopic and elemental analysis. Their molecular structures were determined by single-crystal X-ray diffraction analysis. On activation with diethylaluminum chloride (Et 2 AlCl), all the nickel complexes exhibited good catalytic activities for ethylene oligomerization, and the nickel(II) complexes bearing 2-(1-methyl-2-benzimidazole)-6-(1-aryliminoethyl)pyridines showed good activities up to 5.87 × 10 5 g mol -1 (Ni) h -1 atm -1 . The various reaction parameters were investigated in detail, and the results revealed that both the steric and electronic effects of ligands strongly affect the catalytic activities of their nickel complexes as well as different coordination style.

A series of 2-(2-benzhydrylnaphthyliminomethyl)pyridine derivatives (L1-L3) was prepared and used to synthesize the corresponding bis-ligated nickel(II) halide complexes (Ni1-Ni6) in good yield. The molecular structures of representative complexes, namely the bromide Ni3 and the chloride complex Ni6, were confirmed by single crystal X-ray diffraction, and revealed a distorted octahedral geometry at nickel. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all nickel complex pre-catalysts exhibited high activities (up to 2.02 × 10(7) g(PE) mol(-1)(Ni) h(-1)) towards ethylene polymerization, producing branched polyethylene of low molecular weight and narrow polydispersity. The influence of the reaction parameters and the nature of the ligands on the catalytic behavior of the title nickel complexes were investigated.

The series of acenaphthylene-1-[2,6-bis(bis(4-fluorophenyl)methyl)-4-methylphenylimino]-2-arylimine derivatives and their dichloronickel complexes were synthesized and fully characterized as well as the single-crystal X-ray diffraction of representative nickel complexes, revealing a distorted tetrahedral geometry. Upon activation with either MAO or Et2AlCl, all nickel complexes showed high activities in ethylene polymerization; moreover, their catalytic systems showed better thermal stabilities on being manipulated at 80 °C as the industrial operating temperature.

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A series of 1-(2-benzhydryl­naphthylimino)-2-phenylimino­acenaphthylene derivatives (L1–L5) was synthesized, characterized, and then reacted with (DME)NiBr2 to form the corresponding [1-(2-benzhydryl­naphthylimino)-2-phenylimino­acenaphthyl]nickel bromides (C1–C5). All nickel complexes were fully characterized by their FT-IR spectra and elemental analysis. The molecular structures of the representative complexes C1 and C4 were also determined by single-crystal X-ray diffraction. On activation with either methylaluminoxane (MAO) or diethylaluminum chloride (Et2AlCl), all title nickel complexes showed high activities toward ethylene polymerization; the resulting polyethylenes showed molecular weights higher than those obtained by using the nickel analogues bearing (2-benzhydryl­naphthylimino)pyridines and also had branches lower than those obtained by using other diiminoacenaphthylnickel analogues. Therefore, the modification of ligands could affect the catalytic behavior of their nickel complexes in order to tailor the molecular weights and branches of the resulting polyethylenes.

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