Figure 1. Molecular structure of trans-[Ru(depe)2Cl2][PF6] in the crystals. Displacement ellipsoids are shown at the 50% probability level. Hydrogen atoms have been omitted for clarity. Redox chemistry of oxo and nitrido Ru or Os complexes containing polypyridine, Schiff base, or porphyrin ligands has been extensively studied. Especially the polypyridyl complexes of ruthenium have been known as excellent photosensizers in the use of photovoltaic cells based on nanocrystalline TiO2 films as well. Multiple bonding with O and/or N atoms of the oxo/nitrido ligands bonded to the metal stabilizes oxidants and promotes the conversion of organic and inorganic substrates via electron transfer, oxygen or nitrogen atom transfer, hydride transfer, and proton-coupled electron transfer pathways. Many researchers have endeavored to find out other sources of chelating ligands. We have been developed the synthetic chemistry of the reactive complexes of the diphosphine ligands coordinated to the ruthenium metal. One of general methods for the preparation of reactive Ru-oxo complexes is using the oxidation of the corresponding Ru-aqua complexes, which can be obtained from the reaction of Ru-chloro complexes with Ag in water. We applied it to the synthesis of the Ru-dioxo complexes surrounded by the diphosphine ligands. [Ru(dmpe)2Cl2] and [Ru(depe)2Cl2] complexes were isolated by the reactions of [Ru(PPh3)3Cl2] with dmpe (1,2-bis(dimethylphosphino)ethane) and depe (1,2-bis(diethylphosphino)ethane), respectively, in acetone under refluxing, then aquated the corresponding Ru-dichloro complexes by AgClO4 in H2O. We tried to prepare Ru(II) diaqua complexes, which have been known as the precursor to lead to Ru-dioxo complexes, however it turned out to be unsuccessful.