The cyclohexyl-substituted salicylaldiminato-Ni(II) complex [O-(3-C6H11)(5-CH3)C6H2CH=N-2,6-(C6H3Pr2)-Pr-i]Ni(PPh3)(Ph) (4) has been synthesized and characterized with H-1 NMR and X-ray structure analysis. In the presence of phosphine scavengers such as bis(1,5-cyclooctadiene)nickel(0) [Ni(COD)(2)], triisobutylaluminum (TIBA), and triethylaluminum (TEA), 4 is an active catalyst for ethylene polymerization and copolymerization with the polar monomers tert-butyl-10-undecenoate, methyl-10-undecenoate, and 4-penten-1-ol under mild conditions. The polymerization parameters affecting the catalytic activity and viscosity-average molecular weight of polyethylene, such as the temperature, time, ethylene pressure, and catalyst concentration, are discussed. A polymerization activity of 3.62 x 10(5) g of PE (mol of Ni h)(-1) and a weight-average molecular weight of polyethylene of 5.73 x 10(4) g-mol(-1) have been found for 10 mumol of 4 and a Ni(COD)(2)/4 ratio of 3 in a 30-mL toluene solution at 45 degreesC and 12 x 10(5) Pa of ethylene for 20 min. The polydispersity index of the resulting polyethylene is about 2.04. After the addition of tetrahydrofuran and Et2O to the reaction system, 4 exhibits still high activity for ethylene polymerization. Methyl-10-undecenoate (0.65 mol %), 0.74 mol % tert-butyl-10-undecenoate, and 0.98 mol % 4-penten-1-ol have been incorporated into the polymer. (C) 2004 Wiley Periodicals, Inc.