Stereoregular polymerization of phenylacetylenes catalyzed by [hydridotris(pyrazolyl)borato]rhodium(I) complexes

Rhodium(I) tris(pyrazolyl)borate complexes Tp(R2)Rh(cod) (R = Me, Ph, i-Pr) were found to serve as efficient catalysts for highly stereoregular polymerization of phenylacetylene derivatives (p-YC6H4C drop CH; Y double bond H, Me, Cl, CN, CO2Me, COMe, NO2) to give poly(phenylacetylene) species having a head-to-tail, cis-transoidal structure. The catalytic activity was strongly affected by the substituents (R) at the 3- and 5-positions of the pyrazolyl groups, and the more sterically demanding R groups led to higher catalytic activity.