HYDRIDE ADDITION TO COORDINATED S(2)CPR(3) LIGANDS IN MONONUCLEAR MN AND RE COMPLEXES - PHOSPHANE-DITHIOFORMATE ADDUCTS AS 5-ELECTRON BRIDGING LIGANDS

The cationic tetracarbonyl complex cis-[Mn(CO)(4)(S(2)CPCy(3))](+) und ergoes addition of hydride ion to the central carbon of the S(2)CPR(3) ligand to afford, after spontaneous dimerization with loss of CO, the dimer [Mn-2(CO)(6){[mu-S2C(H)PCy(3)}(2)] (5a), which was characterize d by analytical and spectroscopic methods as well as by X-ray diffract ion. In the molecule of 5a each S2C(H)PCy(3)(-) ligand is coordinated to one manganese in an eta(2)-S,S' chelate fashion, and one sulfur of each ligand serves as a bridge to bind the other manganese atom, thus forming a distorted Mn2S2 square. This appears to be a very stable arr angement. Compound 5a can be more easily prepared by treating the perc hlorato complex [Mn(CO)(3)(S(2)CPCy(3))(OClO3)] (2a) with NaBH4. This procedure is general and can be used for the preparation of several de rivatives containing either manganese or rhenium [M(2)(CO)(6){mu-S2C(H )PR(3)}(2)] 5a-d. The reaction of cationic tricarbonyl complexes [M(CO )(3)(S(2)CPR(3))(PPh(3))]PF6 (M = Mn, Re) with NaBH4 produces the same dimers 5a or 5c by displacement of the PPh(3) Ligand. Treatment of th e dimer 5a with excess PEt(3) or P(OMe)(3) leads to the cleavage of th e bridges and loss of one CO and the PR(3) group from the S2C(H)PR(3) unit to afford ultimately the dithioformate complexes [Mn(CO)(2)(S2CH) (L)(2)] [L = PEt(3), P(OMe)(3)].