PHOTOCHEMISTRY OF [(ETA(5)-C5H5)RU(CO)(2)](2) IN POLAR AND NONPOLAR-SOLVENTS

The photochemistry of bridged and non-bridged isomers of the title com plex was studied in various solvents by flash photolysis and continuou s irradiation at different wavelength regions. Reactive decay of the e xcited non-bridged isomer produced either a polymer (in neat non-polar solvents) or monomeric [CpRu(CO)(2)Cl] complex (in non-polar solvents containing CCl4) via homolytic cleavage of the Ru-Ru bond. Polymeriza tion was preceded by generation of a transient species (IP1) with lamb da(max) approximate to 470 nm and tau(1/2) approximate to 4 ms, which was tentatively formulated as a trimer [CpRu(CO)(2)](3). Photolysis of the bridged isomer generated another transient species, IP2, characte rized by the solvent-dependent absorption at 315-330 nm, assigned to t he mono-bridged dimer with coordinated solvent L, [Cp(CO)(2)Ru(mu-CO)R u(CO)LCp]. The IP2 properties and reactivity led to conclusion that ph otocleavage of the CO-bridge is the mode for the bridged isomer. (C) 1 997 Elsevier Science S.A.