High-oxidation-state decay of mononuclear complexes [RuTB(H2O)](2+) (X2+, where B = 2,2'-bpy or bpy for X = 1; B = 5,5'-F-2-bpy for X = 2; B = 6,6'-F-2-bpy for X = 3; T = 2,2':6',2?-terpyridine) oxidized with a large excess of Ce-IV generates a manifold of polynuclear oxo-bridged complexes. These include the following complexes: (a) dinuclear [TB-Ru-IV-O-Ru-IV-(T)(O)OH2](2+) (1-dn(4+)), [TB-Ru-III-O-Ru-III-T(MeCN)(2)](4+) (1-dn-N4+), and {[Ru-III(trpy)(bpy)](2)(mu-O)}(4+) (1-dm(4+)); (b) trinuclear {[Ru-III(trpy)(bpy)(mu-O)](2)Ru-IV(trpy)(H2O)}(ClO4)5(6+) (1-tr6+) and {[Ru-III(trpy)(bpy)(mu-O)](2)Ru-IV(pic)(2)}(ClO4)(4) (1-tr-P4+, where P is the 2-pyridinecarboxylate anion); and (c) tetranuclear [TB-Ru-III-O-TRuIV(H2O)-O-TRuIV(H2O)-O-Ru-III-TB]8+ (1-tn(8+)), [TB-Ru-III-O-TRuIV(AcO)-O-TRuIV(AcO)-O-Ru-III-TB](6+) (1-tn-Ac6+), and [TB-Ru-II-O-TRuIV(MeCN)-O-TRuIV(MeCN)-O-Ru-II-TB](6+) (1-tn-N6+). These complexes have been characterized structurally by single-crystal X-ray diffraction analysis, and their structural properties were correlated with their electronic structures. Dinuclear complex 1-dm(4+) has been further characterized by spectroscopic and electrochemical techniques. Addition of excess CeIV to 1-dm(4+) generates dioxygen in a catalytic manner. However, resonance Raman spectroscopy points to the in situ formation of 1-dn(4+) as the active species.