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.