The reactions of bidentate diimine ligands (L-2) with binuclear [Ru(L-1)(CO)Cl-2](2) complexes [L-1 not equivalent to L-2 = 2,2'-bipyridine (bpy), 4,4'-dimethyl-2,2'-bipyridine (4,4'-Me(2)bpy), 5,5'-dimethyl-2,2'-bipyridine (5,5'-Me(2)bpy), 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (4,7-Me(2)phen), 5,6-dimethyl-1,10-phenanthroline (5,6-Me(2)phen), di(2-pyridyl)ketone (dpk), di(2-pyridyl)amine (dpa)] result in cleavage of the dichloride bridge and the formation of cationic [Ru(L-1)(L-2)(CO)Cl](+) complexes. In addition to spectroscopic characterization, the structures of the [Ru(bpy)(phen)(CO)Cl](+), [Ru(4,4'-Me2bpy)(5,6-Me2phen)(CO)Cl]+ (as two polymorphs), [Ru(4,4'-Me2bpy)(4,7-Me2phen)(CO)Cl]+, [Ru(bpy)(dpa)(CO)Cl](+), [Ru(5,5'-Me(2)bpy)(dpa)(CO)CI](+), [Ru(bpy)(dpk)(CO)Cl](+), and [Ru(4,4'-Me(2)bpy)(dpk)(CO)Cl](+) cations were confirmed by single crystal X-ray diffraction studies. In each case, the structurally characterized complex had the carbonyl ligand trans to a nitrogen from the incoming diimine ligand, these complexes corresponding to the main isomers isolated from the reaction mixtures, The synthesis of [Ru(4,4'-Me(2)bpy)(5,6-Me(2)bpy)(CO)(NO3)](+) from [Ru(4,4'-Me(2)bpy)(5,6-Me(2)bpy)(CO)Cl](+) and AgNO3 demonstrates that exchange of the chloro ligand can be achieved.