“…In fact, the formation of mononuclear ruthenium bipyridine carbonyl complexes, such as [Ru(k 2 -bpy-N,N)(CO) 2 Cl 2 ], gives a single isomer or a mixture depending of the choice of solvent and the starting ruthenium reagent. 4 Recently, we found that the reaction of the binuclear complex [{Ru(CO) 3 Cl 2 }] 2 with an unsymmetrical quinolinquinone ligand affords mononuclear complexes of the type [Ru(k 2 -N,O)(CO) 2 Cl 2 ] (N,O = 6-methoxybenzo[g]quinoline-5,10-dione), which shows a cis(CO)-transCl configuration. 5 Following our interest in the reactions of the dimer complex [{Ru(CO) 3 Cl 2 } 2 ] with bidentate unsymmetrical ligands, we report here the synthesis, spectroscopic and X-ray characterization of the neutral complex dicarbonyldichloro{2-(diphenylphosphineoxide)pyridine}ruthenium(II), [Ru(k 2 -PyPOPh 2 -N,O)(CO) 2 Cl 2 ].…”