Peroxide oxygenation of mu-thiolate-mu-sulfide Mo(V) dimer complexes of the type [Mo-2(NAr)(2)(S2P(OEt)(2))(2)(mu O(2)CMe)(mu-SR)(mu-S)] yielded Mo-2(mu-SO) and Mo-2(mu-SO2) complexes, demonstrating the reactivity sequence mu-S > mu-SO much greater than mu-SR. Inversion isomers of the pyramidal sulfur site in the mu-SO bridge were observed, and the pyramidicity was confirmed crystallographically. Visible light photolysis of the Mo-2(mu-SO2) complex liberated SO from the SO2 bridge and produced Mo-2(mu-O) compounds. Crystallography of analogous Mo-2(mu-S), Mo-2(mu-SO), Mo-2(mu-SO2), and Mo-2(mu-O) complexes provided structural comparisons related to variations in the bridge functionality. For 2, Mo2C31H44N2O6P2S6 : a = 13.604(5) Angstrom, b = 15.280(4) Angstrom, c = 12.502(2) Angstrom, alpha = 93.36(2)degrees, beta = 112.00 (2)degrees, gamma = 76.01(2)degrees, triclinic, , Z = 2. For 3, Mo2C31H44N2O7P2S6 : a = 12.535(2) Angstrom, b = 25.299(9) Angstrom, c = 13.989(5) Angstrom, beta = 99.99(2)degrees, monoclinic, P2(1)/n, Z = 4. For 4, Mo2C31H44N2O8PZS6 : a = 12.591(9) Angstrom, b = 25.34(1) Angstrom, c = 14.048(3) Angstrom, beta = 100.79(4)degrees, monoclinic, P2(1)/n, Z = 4. For 5, Mo2C31H44N2O7P2S5 : a = 13.731(5) Angstrom, b = 19.267(4) Angstrom, c = 16.652(5) Angstrom, beta = 104.78(3)degrees, monoclinic, P2(1)/n, Z = 4.