Stereoselective living polymerization of phenylacetylene promoted by rhodium catalysts with bidentate phosphines

Polymerization of phenylacetylene to give highly stereoregular cis-transoid polyphenylacetylene is accomplished by use of [Rh(nbd)(OMe)]2 (nbd=norbornadiene) and Ph2P(CH2)xPPh2 (x=2, dppe; x=3, dppp; x=4, dppb). The catalytic system employing the ligand dppb promotes formation of polymer products with low polydispersities. The polymerization is of living nature, as proved by the dependence of polymer molecular weight on conversion and on initial monomer concentration, with molecular weight distributions always maintained within a narrow range. NMR studies of the catalytic system provide information on the rhodium chemistry involved, as well as useful means of comparison to other rhodium–phosphine catalytic systems.