Ligand reactivity was demonstrated for sulfide alkylation, thiolate dealkylation, and dithiophosphate de-esterification within molybdenum(V) dimers. The cationic complex [Mo(2)(NC(6)H(4)Me)(2)(S(2)P(OEt)(2))(2)(&mgr;-O(2)CMe)(&mgr;-SR)(2)](+) was inductively activated toward thiolate C-S and dithiophosphate C-O heterolyses. The dealkylations were studied using anionic nucleophiles, and various reactivity patterns were characterized. The de-esterification of the diethyl dithiophosphate ligands produced complexes containing the rare monoester EtO(O)PS(2)(2)(-) ligand. This ligand's phosphoryl group was poorly nucleophilic but weakly basic. Crystallographic comparisons between the activated cation and the neutral complex [Mo(2)(NC(6)H(4)Me)(2)(S(2)P(OEt)(2))(2)(&mgr;-O(2)CMe)(&mgr;-S)(&mgr;-SMe)] were conducted to delineate structural differences related to the activation. A crystallographic study was also done of the complex [Mo(2)(NC(6)H(4)CH(3))(2)(S(2)P(OEt)(2))(S(2)P(O)OEt)(&mgr;-O(2)CMe)(&mgr;-SEt)(2)], which provided internal comparison of monoester EtO(O)PS(2)(2)(-) and diester (EtO)(2)PS(2)(-) ligand types.

The SO bridge of the complex, [Mo(2)(NTo)(2)(S(2)P(OEt)(2))(2)(mu-O(2)CMe)(mu-SBn)(mu-SO)], 1, displayed nucleophilicity at O, giving alkylation products [Mo(2)(NTo)(2)(S(2)P(OEt)(2))(2)(mu-O(2)CMe)(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)(S(2)P(OEt)(2))(2)(mu-O(2)CMe)(mu-S)(mu-SOR)], 5; de-esterification of a dithiophosphate ligand in 4(+) gave [Mo(2)(NTo)(2)(S(2)P(O)(OEt))(S(2)P(OEt)(2))(mu-O(2)CMe)(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.