Kinetics and mechanism of polymerization of phenylacetylene initiated by (phenylmethoxycarbene)pentacarbonyltungsten(0)

Abstract

The kinetics of polymerization of phenylacetylene in CDCl₃ solution, intiated by Ph(MeO)CW(CO)₅, has been followed under various conditions by in situ analysis of monomer (A) and initiator (F) using ¹H n.m.r. spectroscopy. In degassed solution at 332 K the polymerization is zero order with respect to A and fractional order (0.7) with respect to F, the variation of rate with temperature (323–343 K) corresponding to an apparent activation energy of 116 kJ mol^–1.

The reaction is retarded by the presence of CO, O₂ or air, but not by N₂. Under 1 atm CO or air the reaction becomes first order with respect to F but remains zero order with respect to A. The mechanism of initiation and propagation is discussed in terms of elementary steps involving formation and reactions of metallacarbenes, metallacarbene–monomer complexes and metallacyclobutenes.