A series of titanium complexes Ar[O,E]Cp*TiCl(Cp* = C5Me5,Ar = 1,2-phenylene,E = NH(1a);Ar = 1,2-phenylene,E =O(1b);Ar = 2,2-diphenylene,E = O(lc);Ar = 2,2-dinaphthalene,E = O(1d))has been prepared by the reaction of corresponding phenol derivatives with Cp*TiCl3 in the presence of excessive triethylamine.Under the conditions of low Al/Ti molar ratio(e.g.500)and high reaction temperatures(≥ 70℃),all the titanium complexes display higher catalytic activities towards the syndiospecific polymerization of styrene,in the presence of modified methylaluminoxane (MMAO)as a cocatalyst,than their mother complex Cp*TiCl3.The catalyst activities and polymer yields as well as polymer properties are considerably affected by the steric and electronical effects of the bidentate ligands.