The SO bridge of the complex, [Mo-2(NTo)(2)(S2P(OEt)(2))(2)(mu-O2CMe)(mu-SBn)(mu-SO)], 1, displayed nucleophilicity at O, giving alkylation products [Mo-2(NTo)(2)(S2P(OEt)(2))(2)(mu-O2CMe)(mu-SBn)(mu-SOR)](+), 4(+) which contained the thioperoxide bridge. These cations were then subject to nucleophilic attack by two pathways. Debenzylation of the bridge thiolate in 4(+) afforded neutral [Mo-2(NTo)(2)(S2P(OEt)(2))(2)(mu-O2CMe)(mu-S)(mu-SOR)], 5; de-esterification of a dithiophosphate ligand in 4(+) gave [Mo-2(NTo)(2)(S2P(= O)(OEt))(S2P(OEt)(2))(mu-O2CMe)(mu-SBn)(mu-SO)], 6, which contained a monoester, dithiophosphate ligand. Complex 1 gave a slow and clean reaction in the crystalline state, further demonstrating its nucleophilicity by attacking a neighboring molecule in its lattice. X-ray crystallography confirmed the thioperoxide linkage and revealed structural similarities of the Mo-2(mu-SOR) unit to sulfenate esters (RSOR) and related derivatives.