Irradiation of Cp*Ru(CO)2CH3 (1) in C6D6 at room temperature yields Cp*Ru(CO)2C6D5 and CH3D (where Cp* = n5-C5Me5). Cp*Ru(CO)2CD3 (2) has also been prepared and similar irradiation in C6H6 yields Cp*Ru(CO)2C6H5 (3) and CD3H. This latter reaction confirms that it is the methyl group bonded to ruthenium that is involved in the C-H activation process and not the methyl groups on the Cp* ligand system. The compound Cp*Ru(CO)2C6H5 (3) has been prepared for the first time in good yield by the reaction of Cp*Ru(CO)2Br with NaBPh4. X-ray crystal structures of both Cp*Ru(CO)2CH3 (1) and Cp*Ru(CO)2C6H5 (3) have been determined and the results are reported and discussed. © 2008 Elsevier B.V. All rights reserved.