Radical Polymerization of Styrene and Methyl Methacrylate with Ruthenium(II) Complexes

Abstract

Methylation of [TpRu(CO)2(THF)][PF6] yields the Ru(II) complex TpRu(CO)2(Me), and reaction of TpRu(CO)2(Me) with Me3NO in refluxing acetonitrile yields TpRu(CO)(CH3)(NCMe) (Tp = hydridotris(pyrazolyl)borate). Reactions of TpRu(CO)(CH3)(NCCH3) with CD3CN indicate that the bound acetonitrile ligand undergoes exchange to yield TpRu(CO)(CH3)(NCCD3), and the rates of the exchange reactions are independent of CD3CN concentration. At elevated temperatures catalytic quantities of TpRu(CO)(CH3)(NCMe) in the presence of styrene result in the production of polystyrene. The dependence of polystyrene molecular weight on benzene/cumene molar ratios indicates a radical polymerization mechanism. Styrene polymerization also occurs in the presence of carbon tetrachloride or methyl dichloroacetate. In addition, the polymerization of methyl methacrylate in the presence of TpRu(CO)(CH3)(NCMe) with carbon tetrachloride or methyl dichloroacetate has been observed at 90 °C.