An efficient rhodium(I) initiator for stereospecific living polymerization of phenylacetylenes

A new rhodium (I) initiator system for stereospecific living polymerization of phenylacetylenes is reported that is easily prepared and displays a much higher reaction rate and initiation efficiency. The reaction with the new Rh initiator proceeding homogeneously in THF is 3-4 times faster than with Rh(C≡CC6H5) (2,5-norbornadiene)-CP(C6H5)3]2 (1). The number-average molecular weight (Mn) of the products obtained with 100% conversion of the monomer increased proportionally from the initial phenylacetylene/Rh feed ratio up to 3.5 × 104 with a 250:1 feed ratio, in which the initial concentration of phenylacetylene was kept constant. The polydispersity value of the polymer remained within the narrow range 1.11-1.15. The Mn values indicate that the initiation efficiency value of the initiating system is nearly doubled compared with the value obtained with (1).