Three new alpha-diimine Ni(II) complexes {bis[N,N'-(4-fluoro-2,6-diphenylphenyl)imino]acenaphthene} dibromonickel 4a, {bis[N,N'-(4-chloro-2,6-diphenylphenyl)imino]acenaphthene}dibromonickel 4b, and {bis[N,N'-(4-methyl-2,6-diphenylphenyl)imino]acenaphthene}dibromonickel 4c, were synthesized and characterized. The crystal structure of the complex 4a was determined by X-ray crystallography. Complex 4a has pseudo-tetrahedral geometry about the nickel center, showing C-2v molecular symmetry. These complexes, activated by diethylaluminum chloride (DEAC) were tested in the polymerization of ethylene under mild conditions. Complex 4a bearing 2,6-diphenyl and strong electron-withdrawing 4-fluorine groups, activated by diethylaluminum chloride (DEAC) shows highly catalytic activity for the polymerization of ethylene [4.95 x 10(6) g PE/(mol Ni h bar)] and produced dendritic polyethylene (153.3 branches/1000 C). The dendritic polyethylene particle size obtained by 4a/DEAC can be controlled in the 1-20 nm under 0.2 bar ethylene pressure, and could be expected to become a nano-targeted drug carrier after modified with water-soluble oligo(ethylene glycol) (OEG). (C) 2013 Elsevier B.V. All rights reserved.