Several dicarbonyl-(π-cyclopentadienyl)ruthenium complexes containing ruthenium to silicon, germanium, tin, cobalt, and rhenium bonds have been prepared, and spectroscopic evidence for a ruthenium–nickel complex has been obtained. Controlled pyrolysis of [(π-C5H5)Ru(CO)2]2 gives the tetrameric [(π-C5H5)Ru(CO)]4, and traces of a higher molecular-weight complex. Comparisons with the corresponding iron complexes have been made where appropriate.