Abstract: A series of β-diketoiminato ligands with different phenyl substituents and their Ni(Ⅱ) complexes were synthesized. The ligands and the Ni(Ⅱ) complexes were characterized by elemental analysis, 1H NMR and X-ray crystallography. The reaction of NiCl₂ with lithium salt of the ligand and phenyl substituents in THF gives bis(β-diketoiminato) Ni(Ⅱ) complex 1, while the reactions with lithium salt of the ligand with 2,6-Me₂C₆H₃ or 2,6-iPr₂C₆H₃ substituents produce dimeric β-diketoiminato Ni(Ⅱ) chloride complexes 2 and 3. When activated by AlR₃, complexes 2 and 3 exhibit high catalytic activities for ethylene polymerization, and polyethylenes with a high molecular weight were abtained.

Key words: Dikeotiminate, Late transition metal catalyst, Ethylene polymerization