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A series of new, electron-poor neutral κ 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 κ 2 - N, O -2, 6-R 2 C 6 H 3 N C (H) C (COCF 3) C (O) CF 3 Ni (L) Me (4a, R = i Pr, L = pyridine; 4b, R = 3, 5- (CF 3) 2 C 6 H 3, L = pyridine; 5b, R = 3, 5- (CF 3) 2 C 6 H 3, L = PPh 3) were prepared. The complexes are very active in aqueous emulsions, with 1. 4 × 10 4 TO h -1 for 4a (50 °C) and 1. 9 × 10 4 TO h -1 for 4b (70 °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 × 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 °C are obtained.
Yu et al. (2007) studied this question.