Syndiotactic polystyrene (sPS) is a new class of thermoplastics and is unusual among polystyrenes for its properties．Since Ishihara reported on the titanium complexes with mono-cyclopentadienyl ligand for production of sPS

a lot of catalysis for styrene syndiotactic polymerization has been reported in the literature．A series of half-metallocene complexes have been reported in our studies

these catalysts have high stability and activity for olefin polymerization with low molar ratio of aluminium／titanium and produce polymers with different chain microstructures．In the paper

synthesis of half-metallocene complexes [CpTi(dbm)Cl2] and [CpTi(dbm)2Cl] containing β/i>-diketone ligand are discribed．It is proved by the experiments that [CpTi(dbm)Cl2] is active for styrene polymerization at 40℃ with MAO activation

and exhibits higher activity than CpTiCl3．Giving the polymers with high syndiotacticity.For the [CpTi(dbm)Cl2]／MAO system

the activity is “up and down” type with increase in the Al／Ti molar ratio

and up to the highest when the Al／Ti molar ratio is about 500

10.7×l05 gPS／molTi·h or so；also the active decreases when the polymerization time is too high．The polymers prepared by [CpTi(dbm)Cl2] were extracted with boiling n-butanone and characterized by 13C-NMR．