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 -YC 6 H 4 C⋮CH; Y = H, Me, Cl, CN, CO 2 Me, COMe, NO 2 ) 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.