A series of new, electron-poor neutral kappa(2)-N,O chelated Ni(II) complexes were studied for ethylene polymerization in aqueous emulsion. Complexes based on enolatoimine ligands bearing electron-withdrawing trifluoromethyl and trifluoroacetyl groups [kappa(2)-N,O-{2,6-R2C6H3NC(H)C(COCF3)C(O)CF3}]Ni(L)Me (4a, R = Pr-i, L = pyridine; 4b, R = 3,5-(CF3)(2)C6H3, L = pyridine; 5b, R = 3,5-(CF3)(2)C6H3, L = PPh3) were prepared. The complexes are very active in aqueous emulsions, with 1.4 x 10(4) TO h(-1) for 4a (50 degrees C) and 1.9 x 10(4) TO h(-1) for 4b (70 degrees C), affording stable polyethylene dispersions. The phosphine complex 5b is active in the absence of a phosphine scavenger, with similar activities as 4b. Polyethylenes of typically M-w 3 x 10(4) g mol(-1) (M-w/M-n 2.0-2.5) with 25-50 branches per 1000 carbon atoms and T-m 94-112 degrees C are obtained.