Atom Transfer Radical Polymerization of Styrene and Methyl Methacrylate Induced by RhI(cycloocta-1,5-diene) Complexes

Abstract

Rh(I)(diene) complexes, di(μ-docosanoato)bis[(η2:η2-cycloocta-1,5-diene)rhodium(I)] (1) and bis(μ-4-methylphenolato)bis[(η2:η2-cycloocta-1,5-diene)rhodium(I)] (2) are introduced as a new class of catalysts for the atom transfer radical polymerization (ATRP) of vinyl monomers and provide new example of an involvement of rhodium compounds in radical reactions. Single complexes 1 and 2 promote a controlled radical polymerization of methyl methacrylate and styrene affording a medium to good yield of high-molecular-weight polymers with polydispersity index, Mw/Mn, values ranging from 1.45 to 1.65. However, the initiator efficiency found for these reaction systems is rather low, from 0.04 to 0.20. The addition of (Bu)2NH to these polymerization systems has a remarkable positive influence on the catalyst activity and the polymerization control, particularly, in the systems involving complex 1, for which approximately tenfold increase in the initiator efficiency, up to 0.85, and decrease in the polydispersity index, to the value 1.27, has been observed. Dissociation of dinuclear Rh(I)(diene) species to the mononuclear ones is suggested as an important part of the mechanism lying behind the effect of (Bu)2NH additive.