Monocyclopentadienyl Titanium Catalyst

Monocyclopentadienyl titanium complexes are active catalysts for syndiotactic polymerization of styrene. The activity is severely suppressed when the Cp ligand has a substituent with a Lewis basic heteroatom. The active species is a titanium cation generated by the usual cocatalyst. Electron paramagnetic resonance and polymerization studies of a series of monocyclopentadienyl titanium precursors with different propensity for reduction showed that both the tetravalent and trivalent Ti+ species are active, with the former having the greater activity than the latter. Very stable catalysts have been found as a result. In contrast, monocyclopentadienyl titanium complexes are poor for ethylene or propylene polymerization; but the activity is greatly improved with a coordinative substituent on the Cp ligand.