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 (1c); 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 (≥ 70οC)

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.