Liquid crystalline titanocene with catalytic activity for polymerizations of acetylene derivatives

Two kinds of liquid crystalline (LC) titanocenes have been synthesized with an aim to construct a new type of anisotropic polymerization field. The titanocene derivatives were prepared by introducing LC groups into cyclopentadienyl ligands as substituents, (PCH506Cp)2TiCl2 (1) or coordinating them to titanium atom as ligands, Cp2Ti(PCH5060)2 (2). Observations of polarizing optical microscope and measurements of DSC indicated that 2 is the first titanium complex exhibiting a thermotropic LC phase. We found that both the titanocene derivatives can polymerize phenylacetylenes to give poly(phenylacetylene)s with an aid of triethylaluminium used as a cocatalyst. Molecular weights and polymerization degrees of the polymers were comparable or superior to those by catalysts such as a titanocene dichloride [Cp2TiCl2] and a tetra-n-butoxytitanium [Ti(O-n-Bu)4]. The LC titanocene derivative (2) was also confirmed to have a high catalytic activity for acetylene polymerization. These results should shed light on development of novel anisotropic reaction field available for syntheses of directly aligned conducting polymers.