A square-shaped tetranuclear ruthenium(II) complex, [(Ru4Cl5)-Cl-II(bpmpm)(2)](3+) [1; bpmpm = 4,6-bis[[N,N-bis(2'-pyridylmethyl)amino]methyl]pyrimidine], exhibited four reversible and stepwise one-electron-oxidation processes: chemical oxidation of 1 formed three different mixed-valence states, in one of which the charge is partially delocalized on the two Ru centers, to be evidenced by observation of an intervalence charge-transfer absorption band, categorized into the RobinDay class II.