Equilibrium between CO-bridged and non-bridged forms of [(η5-C5H5]Ru(CO)2]2 and selective photoreactivity of the non-bridged form

The reaction volumes, ΔV for the equilibrium between CO-bridged and non-bridged forms of the [(η5-C5H5)Ru(CO)2]2 complex in isooctane, isopropanol and acetonitrile were determined spectrophotometrically. The values of ΔV show that an increase in pressure facilitates formation of the CO-bridged form. The effect of pressure is discussed and compared to that of temperature and solvent polarity. Selective photolysis of the non-bridged form in toluene induces the symmetrical cleavage of the Ru--Ru bond to give two [(η5-C5H5)Ru(CO)2]. radicals. EPR experiments with nitrosodurene spin trap indicate that the ruthenium organometallic radicals activate the C--H bond and abstract an H atom from toluene.