A new series of substituted half-sandwich titanium complexes bearing bridged alkenyl groups [eta(5) -C5H4-(bridge)-(alkenyl)]TiCl3 have been synthesized and characterized. All the titanium complexes display considerable catalytic activity towards the polymerization of styrene in the presence of methylaluminoxane (MAO). Bridging unit between the cyclopentadienyl moiety and the allyl groups plays a crucial role in reactivity and stereoselectivity of styrene polymerization. By modification of the bridging unit, the syndioselectivity of the polymer can be tailor-made, providing a new guideline to design catalyst for polymers having desired properties. (c) 2006 Elsevier B.V. All rights reserved.