Photochemical studies as a function of solvent viscosity. A new photochemical pathway in the reaction of (eta5-C5H4Me)2Mo2(CO)6 with CCl4.

This paper reports the results of a study that used systematic changes in the solvent viscosity to probe the photochemical reactivity of the Cp'2Mo2(CO)6 (Cp' = eta5-C5H4CH3) molecule. The quantum yields for photolysis of Cp'2Mo2(CO)6 in the presence of CCl4 were studied as a function of solvent viscosity. The quantum yields did not decrease to zero with increasing solvent viscosity but rather leveled off at a constant, non-zero value. This result cannot be explained by any of the previously reported radical or Mo-CO dissociation photochemical pathways for this molecule, and therefore an additional photochemical pathway is suggested to be operating in the reaction. The new pathway may involve a reactive isomer of Cp'2Mo2(CO)6 or possibly electron transfer between the excited state of Cp'2Mo2(CO)6 and CCl4.