EQUILIBRIUM BETWEEN CO-BRIDGED AND NON-BRIDGED FORMS OF [(ETA(5)-C5H5]RU(CO)(2)](2) AND SELECTIVE PHOTOREACTIVITY OF THE NON-BRIDGED FORM

The reaction volumes, Delta (V) over bar for the equilibrium between C O-bridged and non-bridged forms of the [(eta(5)-C5H5)Ru(Co)(2)](2) com plex in isooctane, isopropanol and acetonitrile were determined spectr ophotometrically. The values of Delta (V) over bar show that an increa se in pressure facilitates formation of the CO-bridged form. The effec t of pressure is discussed and compared to that of temperature and sol vent polarity. Selective photolysis of the non-bridged form in toluene induces the symmetrical cleavage of the Ru-Ru bond to give two [(eta( 5)-C5H5)Ru(CO)(2)](.) radicals. EPR experiments with nitrosodurene spi n trap indicate that the ruthenium organometallic radicals activate th e C-H bond and abstract an H atom from toluene. (C) 1997 Elsevier Scie nce Ltd.