The syndiospecific polymerization of styrene was investigated with the fluorine-containing half-sandwich complexes eta(5)-pentamethylcyclopentadienyl titanium bis(trifluoroacetate) dimer, eta(5)-octahydrofluorenyl titanium tristrifluoro-acetate, eta(5)-octahydrofluorenyl titanium dimethoxymonotrifluoroacetate, and eta(5)-octahydrofluorenyl titanium tris(pentafluorobenzoate) in comparison to known chloride and methoxide complexes in the presence of relatively low amounts of methylalumoxane and triisobutylaluminum. After the selection of effective reaction conditions for a solvent-free polymerization, the following orders of decreasing polymerization activity of the titanium complexes can be observed: for pentamethylcyclopentadienyl compounds, Cp*Ti(OMe)(3) > [Cp*Ti(OCOCF3)(2)](2)O approximate to Cp*TiCl3, and for octahydrofluorenyl compounds, [656]Ti(OMe)(3) > [656]Ti(OCOC6F5)(3) > [656]Ti(OCH3)(2)(OCOCF3) > [656]Ti (OCOCF3)(3). The [656]Ti complexes, showing the highest polymerization conversions at 70 degrees C and in comparison with the Cp* Ti compounds, turned out to be highly efficient catalysts for the syndiospecific styrene polymerization. The fluorine-containing Cp* and [656]Ti complexes lead to much higher molecular weights than the chloride and methoxide compounds because of a reduction in chain-limiting transfer reactions. The introduction of only one fluorine-containing ligand into the coordination sphere of the metal compound is obviously sufficient for a significant increase in molecular weight. The active polymerization sites of the [656]Ti complexes with methylalumoxane and triisobutylaluminum are extremely stable during storage at room temperature in regard to their polymerization activity.