The acetyls Mo(C(O)Me)(S(2)COR)(CO)(PMe(3))(2) undergo partial desulfurization of the ligated xanthate and coupling of the resulting S atom with the acetyl group to furnish complexes containing coordinated alkoxythiocarbonyl and monothioacetate ligands, Mo(SOCMe)(eta(2)-C(S)OMe)(CO)(PMe(3))(2). Metathetical re placement of the MeCOS(-) ligand by ROCS(2)(-) affords Mo(S(2)COR)(eta(2)-C(S)OR)(CO)(PMe(3))(2), which can be prepared in a one-pot synthesis from Mo(eta(2)-C(O)Me)Cl(CO)(PMe(3))(3) and 2 equiv of KS(2)COR. The structure of the t-Bu derivative has been determined by X-ray crystallography.