Titanatrane Catalysts For Syndiotactic Polystyrene

Syndiotactic polystyrene (sPS) is a kind of engineering thermoplastic obtained by mono-titanocene-catalized polymerization of styrene. The research for new catalysts of sPS with higher ativities is of great value because sPS has wide application in many fields, especially in automobile industry.The catalysts for sPS are mainly half-sandwich Ti[Ⅳ] complexes, of which cyclopentadienyl (Cp) ligands are necessary for their high activities. Ancillary ligands (Non-Cp ligands) can affect the activities. Phenoxy-type ancillary ligands often give catalysts with higher activities. Introduction of the atrane structures to mono-titanocene complexes can also increase the ativities of the catalysts.To combine the positive effect of both the phenoxy-type ligands and the atrane structures, a new kind of Cp*-titanatranes (Cp*=pentamethylcyclopentadienyl) complexes containing phenoxy ligands was synthesized and investigated as catalysts for syndiospecific polymerization of styrene upon activation of modified methylaliminoxane (MMAO).Mannich condensation of suitable phenols, paraformaldehyde and alcoholamines affords the according Mannich base compounds, which are tripod tetradentated ligands for the synthesis of titanatranes. Half-sandwich titanatranes were synthesized by reaction of Cp*TiCl3 and the above Mannich base compounds in the presence of triethylamine.The titanium complexes have the atrane structures. ~1H NMR showed that some signals of the ligands shift downfield when it is complexed with titanium, indicating the influence of strong lewis acidic environment of titanium. The splitting mode suggested that the structures of those titanium compounds were rigid compared with the ligand compounds. X-ray diffraction analysis showed that the geometry of the complexes is a distorted trigonal bipyramide. The titanium atom adopts essentially anη5 bonding posture with regard to Cp* ring and a tetradentate bonding mode with...