A series of (P^N^P)cobalt(Ⅱ) complexes were prepared by the reaction of N-containing diphosphine ligands and anhydrous cobalt dichloride and their catalytic performance in the polymerization of styrene were also investigated.Upon activation with ethylaluminum sesquichloride (EASC)

all these cobalt complexes showed high catalytic activities up to 5.44105 g(PS) mol-1(Co) h-1 for the solution polymerization of styrene in toluene.The reaction parameters

such as styrene concentration (2~4 mL)

Al/Co molar ratio (20~160)

reaction temperature (0~70 ℃) and ligand structure of cobalt complexes were employed in order to study their influences on the polymerization of styrene and the properties of the resulting polymers.The molecular weight

molecular weight distribution and microstructure of the resulting polymers were characterized by GPC and 13C-NMR spectra.The GPC results indicated that all the polystyrenes obtained had low molecular weight (Mn=2000~5900) and narrow molecular weight distribution (1.75~2.05).The 13C-NMR spectra demonstrated that the microstructure of polystyrenes obtained was atactic.