Preparation and characterization of some structural variants of Cp*Ti(1,2-propandiolato) complexes

1,2-Propandiol reacts with Cp*Ti(CH3)3 by rapid liberation of methane to yield a dimetallic complex 6 of the net composition (Cp*Ti)2(1,2-propandiolato)3. The X-ray crystal structure analysis revealed an unsymmetrical bridging between the [Cp*Ti(1,2-propandiolato)] and [Cp*Ti(1,2-propandiolato)2] subunits. Cp*TiCl3 reacts with 1,2-propandiol in a 1:1 stoichiometry in the presence of excess pyridine by replacement of two chlorides by a 1,2-propandiolato ligand. The resulting product was isolated as a dimer 8 and characterized by X-ray diffraction. It exhibits a central Ti2O2 ring that was formed by bridging between the two [Cp*TiCl(1,2-propandiolato)] subunits using the oxygen atoms of the primary end of the ligand. From the reaction mixture a more complicated condensation product 9 was isolated in a small yield that contains two [Cp*TiCl(1,2-propandiolato)] units connected in a similar way by a Cp*-free [Ti(1,2-propandiolato)2] moiety as revealed by its X-ray crystal structure analysis. Complex [Cp*TiCl(1,2-propandiolato)]2 (8) gives an active catalyst for the syndiotactic polymerization of styrene upon treatment with excess methylalumoxane in toluene solution.