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

Methylation of [TpRu(CO) 2 (THF)][PF 6 ] yields the Ru(II) complex TpRu(CO) 2 (Me), and reaction of TpRu(CO) 2 (Me) with Me 3 NO in refluxing acetonitrile yields TpRu(CO)(CH 3 )(NCMe) (Tp = hydridotris(pyrazolyl)borate). Reactions of TpRu(CO)(CH 3 )(NCCH 3 ) with CD 3 CN indicate that the bound acetonitrile ligand undergoes exchange to yield TpRu(CO)(CH 3 )(NCCD 3 ), and the rates of the exchange reactions are independent of CD 3 CN concentration. At elevated temperatures catalytic quantities of TpRu(CO)(CH 3 )(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)(CH 3 )(NCMe) with carbon tetrachloride or methyl dichloroacetate has been observed at 90 °C.