Polymerisation of vinyl monomers by transition-metal allyl compounds. Part II. The polymerisation of methyl methacrylate initiated by allyl-chromium compounds

Abstract

The polymerisation of methyl methacrylate by Cr(allyl)₃ and Cr(2-Me-allyl)₃ in toluene has been studied using kinetic, spectroscopic, and radiochemical techniques. From the data obtained, together with information derived from molecular weights, a mechanism has been obtained which is in accord with the experimental findings. The polymerisation is of the co-ordinated anionic type in which only one of the three allyl groups is involved in the initiation process. A structure (III) is suggested for the propagation centre, in which the metal is in the six-co-ordinate state, and the disposition of the ligands in space is given by (VI). Insertion of the co-ordinated monomer into the attached polymer chain results from collision with a second monomer molecule (VII), tending to increase the co-ordination number of the metal above 6.