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A series of 2,8-bis(1-aryliminoethyl)quinolines [2,8-(2,6-R1 2-4-R2C6H2NCCH3)2C9H5N (L), R1 = Me, Et, or i-Pr, R2 = H or Me] is synthesized and used in the reaction with ferrous or cobaltous chlorides. The corresponding complexes LMCl2 are limitedly formed with ligands containing ortho-methyl groups of the imino phenyl rings (R = H, M = Fe (Fe1), M = Co (Co1); R = Me, M = Fe (Fe2), M = Co (Co2). The X-ray diffraction study reveals a distorted pyramidal geometry of Co1 around the cobalt atom. These complexes, activated with methylaluminoxane (MAO), show unique properties toward ethylene polymerization: no activity observed at low temperature, but high activity achieved at temperatures higher than 80 °C (up to 7.61 × 106 g·mol−1·h−1 at 100 °C). Moreover, the polyethylenes obtained are high molecular weight with narrow molecular distribution. This is the first example of iron and cobalt procatalysts with high activity for ethylene polymerization at high temperature.

The series of N-benzimidazolyl-substituted 2-alkyl-8-(benzimidazol-2-yl)quinolines (L1–L10) and 2-phenyl-8-(benzimidazol-2-yl)quinolines (L11–L14) and their respective bidentate iron(II) dichloride complexes (C1–C14) were synthesized and fully characterized. The molecular structures of a representative ligand (L5) and iron complexes (C2, C7) were determined by X-ray crystal structure analyses, and the distorted tetrahedral coordination geometry was observed around the iron center in both complexes C2 and C7. After activation of the iron complexes with methylaluminoxane, the iron catalysts showed activities up to 106 g·mol–1·h–1 in ethylene polymerization at elevated temperature (100 °C), yielding linear polyethylenes. The reaction parameters of the polymerization reactions were optimized, and the effect of the substituents of the different ligands on the catalytic activity and on the obtained polyethylene was discussed.

A series of 8-(1-aryliminoethylidene)quinaldines and the nickel halides thereof were synthesized and characterized, and the molecular structures of two representative nickel complexes were confirmed by single-crystal X-ray diffraction studies. Upon treatment with diethylaluminium chloride (Et2AlCl), the nickel pro-catalysts exhibited high activity for ethylene oligomerization (1.24–1.83 × 106 g mol-1(Ni) h-1) with good thermal stability at 60 °C under 10 atm of ethylene. The influence of the reaction parameters on the catalytic behaviour was investigated for these nickel-based systems, including variation of Al/Ni molar ratio and reaction temperature. Furthermore, the effect of the ancillary ligand Ph3P was also probed

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