The title compound reacted rapidly with (CNBu)-Bu-t at room temperature by displacing the BF4- ligand and incorporating three molecules of isocyanide to yield the electron-precise complex [Mo2Cp2(mu-PPh2)(2)((CNBu)-Bu-t)(3)(CO)](BF4)(2), which was obtained as a mixture of cis and trans isomers. Reaction with several HERn molecules (HERn = HSPh, HSePh, H2PCy) took place with formal elimination of HBF4 and spontaneous carbonylation to give the electron-precise cations [Mo2Cp2(mu-ERn)(mu-PPh2)(2)(CO)(2)](+). Reactions with several bidentate ligands (L2H) having acidic E-H bonds (2-hydroxypyridine, 2-mercaptopyridine, cathecol, 2-aminophenol, and 2-aminothiophenol) proceeded analogously with deprotonation of these bonds with the preference E = S > O > N. The N,O-donor ligands yielded 32-electron chelate derivatives of the type [Mo2Cp2(O,N-L-2)(mu-PPh2)(2)(CO)]BF4 (L-2 = OC6H4N, OC6H4NH2), whereas the S,N-donors yielded 34-electron, S-bridged complexes [Mo2Cp2(mu-S:S,N-L-2)(mu-PPh2)(2)(CO)]BF4 [L-2 = SC5H4N (Mo-Mo = 2.8895(8) angstrom), SC6H4NH2]. However, reaction with catechol gave a monodentate derivative [Mo2Cp2(O-OC6H4OH)(mu-PPh2)(2)(CO)]BF4. In contrast, reactions of the title complex with several carboxylic acids and related species (acetic, benzoic, and thioacetic acids, acetamide, thioacetamide, and sodium diethyldithiocarbamate) were insensitive to the nature of the donor atoms and gave in all cases 32-electron chelate derivatives of type [Mo2Cp2(kappa(2)-L-2)(mu-PPh2)(2)(CO)]BF4. All of the above cations having Mo-bound OH, NH, or NH2 groups were easily deprotonated upon reaction with 1,8-diazabicycloundec-7-ene (DBU) or other bases to give neutral complexes: which exhibited different coordination motifs depending on the donor atoms, including chelate complexes of the type [Mo2Cp2(kappa(2)-L-s')(mu-PPh2)(2)(CO)] (L-2' = OC6H4O, OC6H4NH), the bridged complexes [Mo2Cp2(mu-S,N:S/N-SC6H4NH)(mu-PPh2)(2)] and [Mo2Cp2{mu-S,N-N(S)CMe}(mu-PPh2)(2)], and the terminal acetylimido complex [Mo2Cp2{N-N(O)CMe}(mu-PPh2)(2)(CO)].