Sulfur insertion into the molybdenum acyl bond of Mo(C(O)R)(S2COR)(CO)(P)(2) complexes. Desulfurization of the xanthate ligand

Partial desulfurization of the xanthate ligand of complexes Mo(C(O)Me)(S2CO R)(CO)(PMe3)(2) (R = Me, 1a; Et, 1b; i-Pr, 1c) occurs at room temperature w ith concomitant insertion of the sulfur atom into the Mo-acetyl bond to pro duce compounds Mo(kappa(2)C,S-C(S)OR)(kappa(2)O,S-OSCMe)(CO)(PMe3)(2) (2a-c ), which contain coordinated, bidentate alkoxythiocarbonyl, ROC(S), and mon othioacetate, MeCOS-, ligands. The analogous rearrangement of the dmpe deri vative 1d (dmpe = Me2PCH2CH2PMe2) yields a similar species, Mo(kappa(2)C,S- C(S)O-i-Pr)((KO)-O-2,S-SOCMe)(Co)(dmpe) (3), but heating at 100 degrees C i s needed in this case. The monothiocarboxylate group of compounds 2 can be replaced by a bidentate xanthate salt, giving Mo(kappa(2)C,S-C(S)OR)(kappa( 2)S,S'-S2COR')(CO)(PMe3)(2) (4), which when R = R' may also be obtained, al beit in lower yields, in a one-pot reaction starting from the chloroacetyl Mo(C(O)Me)Cl(CO)(PMe3)(3) and 2 molar equiv of KS2COR. The facility with wh ich a sulfur atom of the xanthate ligand of compounds 1 inserts into the Mo -eta(2)-acetyl bond is demonstrated by the formation of Mo(kappa(2)C,S-C(S) OR)(kappa(1)S-SC(O)Me)(CO)(2)(PMe3)(2) (R = Me, 5a; i-Pr, 5c) when 1a and 1 c are treated with CO (20 degrees C, 1 atm). The Mo-kappa(2)-C(S)OR linkage of these complexes has been authenticated by X-ray studies carried out wit h 4d and 5c, and it is characterized by a short Mo-C distance of ca. 2.0 An gstrom. Spectroscopically this entity features an IR absorption in the prox imity of 1270 cm(-1) and a low-field C-13 resonance near 295 ppm.