A series of unsymmetrical 1,2-bis(imino) acenaphthenenickel(II) halides containing N-2,6-dibenzhydryl-4-methoxyphenyl - a single bulky group with adjusted electron donating properties - has been synthesized and characterized. These compounds adopt distorted tetrahedral geometry and their H-1 NMR spectra show the paramagnetically shifted peaks. On activation with a low amount of Et2AlCl or ethylaluminum sesquichloride ( EASC), these nickel complexes display high activity in ethylene polymerization, yielding the polyethylene of high molecular weight. They are also stable at elevated temperature; superb activity of 2.51 x 10(6) g of PE (mol of Ni)(-1) h(-1) can be attained at 90 degrees C. The resultant polyethylene exhibits remarkable tensile strength of 24.5 MPa and high elongation at break (602.2%) as well as substantial elastic recovery.