Styrene polymerization with half-sandwich titanium complexes bearing pendent cyclo-alkenyl groups

A new series of substituted half-sandwich titanium complexes bearing bridged cyclo-alkenyl groups [η5-C5H4-(bridge)-(cyclo-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), yielding atactic-rich polystyrene. Experimental results indicate that there might be an interaction between the double bond and the titanium center, which was reflected by 1H NMR spectrum and polymerization behavior. As compared with the size of cyclo-alkenyl ring, the bridging unit plays a crucial role in reactivity and stereoselectivity of styrene polymerization.