Activated by methylaluminoxane, mononuclear bis(hydroxyindanone-iminate)nickel complexes Ni[ArN == CC_2H_3(CH3)C_6H_2(R)O]_2 (Ar = 2,6-i-Pr2C6H3, R = Me (1), R = Cl (2), and R = H (3)) showed good activity for the styrene polymerization. The effect of many reaction parameters including the Al/Ni ratio, tempera- ture, and reaction time on catalytic activities of catalytic systems and the molecular weights of the ob- tained polystyrene was ascertained. The highest activity of 1.34×105 g(PS)·mol^(-1)(Ni)·h^(-1) was obtained under the optimum reaction condition. The 13C NMR spectra of the polymers revealed that the polymer was isotactic-rich atactic polystyrene. And the coordination mechanism was confirmed by the analyses of the polymer chain end-groups.
