Living polymerization of phenylacetylene by rhodium-based ternary catalysts, (diene)Rh(I) complex/vinyllithium/phosphorus ligand. Effects of catalyst components

Abstract

It was proved that a Rh-based ternary catalyst composed of [(nbd)RhCl]2 (nbd: bicyclo[2.2.1]hepta-2,5-diene), (triphenylvinyl)lithium, and triphenylphosphine induces living polymerization of phenylacetylene. [(nbd)RhCl]2 was effective as the main catalyst, whereas neither [(cod)RhCl]2 (cod: 1,5-cyclooctadiene) nor [(coe)2RhCl]2 (coe: cyclooctene) induced living polymerization. The anionic ligands such as chlorine, methoxy, and acetoxy groups in the Rh complex hardly affected the living polymerization. When vinyllithium as second catalyst component possessed a bulky substituent such as phenyl or t-butyl group on its α-carbon, stable vinylrhodium species were generated, which led to living polymerization. At least one substituent was necessary on the β-carbon of the vinyllithium for the living polymerization. Tris(4-substituted phenyl)phosphines worked well as third components among various phosphorus ligands. The polymerization was decelerated as the basicity of the phosphine ligand increased.