CARBON-SULFUR BOND-CLEAVAGE OF S2CPR3 LIGANDS IN DINUCLEAR COMPLEXES PROMOTED BY REDUCTION AND PROTONATION

Complexes [Mn-2(CO)(6)(mu-S2CPR3)] (R = Cy (1a), Pr-i (1b)) are reduce d with Na[Hg] in THF to afford the anions [Mn-2(CO)(6)(mu-S2CPR3)](2-) (2a,b), which give neutral unstable [Mn-2(CO)(6)-(mu-SH) {mu-SC(H)PR3 }(NH3)] (3a,b) upon protonation with excess NH4PF6. The NH3 ligand of 3a,b is readily replaced by PEt3 to obtain [Mn-2(CO)(6)(mu-SH){mu-SC(H )PR3}(PEt3)] (5a,b) as stable crystalline solids, which have been isol ated and characterized. The same reduction/ protonation sequence when applied to the dirhenium analogue [Re-2(CO)(6)(mu-S2CPCy3)] (1c) affor ds stable crystalline [Re-2(CO)(6)(mu-SH){mu-SC(H)PCy3}(NH3)] (6). An X-ray determination revealed that 6 contains one bridging SH- and the novel ligand Cy3PC(H)S- which is bonded as mu(2)-eta(1)(S); eta(2)(C,S '), donating 5e to the metals. Both bridging ligands are produced from the cleavage of one C-S bond of the starting S2CPR3 during the reduct ion/protonation process, which can be regarded globally as hydrogenoly sis of the C-S bond. Additionally, the Re-Re bond is also cleaved duri ng the process. As their dimanganese analogues, 6 undergo easy substit ution of NH3 by PEt3 to give [Re-2(CO)(6)(mu-SH){mu-SC(H)PCy3}(PEt3)] (7). Comparison of the spectroscopic data indicate that both series of compounds are isostructural, with the only difference being the highe r stability of the dirhenium complexes when compared to those of diman ganese.