Liquid crystalline titanocene with catalytic activity for polymerizations of acetylene derivatives

Abstract

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) 2TiCl 2 ( 1) or coordinating them to titanium atom as ligands, Cp 2Ti(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 [Cp 2TiCl 2] 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.