A new tert-butyl-substituted α-diimine compound 1 and its corresponding Ni(II) complex, {bis[N,N -(4-tert-butyl-2,6-dimethylphenyl)imino]acenaphthene}dibromonickel (2), were successfully synthesized and characterized by ¹H NMR, ¹³C NMR, elemental analysis, FT-IR and XPS. Complex 2 with sterically bulky, donating group tert-butyl, activated by diethylaluminum chloride (DEAC) produces very active catalyst system for the polymerization of ethylene [3.15×10⁸ g PE/(mol•Ni•h•MPa)] and led to a branched polyethylene (ca. 131 branches/1000 C). The effects of the Al/Ni molar ratio, polymerization temperature and polymerization time on the catalyst activity also were investigated. The catalyst system 2/DEAC showed the highest activity with the 600 of Al/Ni molar ratio at 5 ℃. The polyethylene (PE) samples were characterized by ¹H NMR, GPC, DSC and TG.

Key words: α-diimine ligand, Nickel(II) complex, late transition metal catalyst, ethylene polymerization