Hydride addition to coordinated S2CPR3 ligands in mononuclear Mn and Re complexes: Phosphane-dithioformate adducts as five-electron bridging ligands

Article abstract of DOI:10.1002/cber.19961291221

The cationic tetracarbonyl complex cis-[Mn(CO)₄(S₂CPCy₃)]⁺ undergoes addition of hydride ion to the central carbon of the S₂CPR₃ ligand to afford, after spontaneous dimerization with loss of CO, the dimer [Mn₂(CO)₆[μ-S₂CSH)PCy₃) ₂] (5a), which was characterized by analytical and spectroscopic methods as well as by X-ray diffraction. In the molecule of 5a each S₂C(H)PCy₃^- ligand is coordinated to one manganese in an η²-S,S′ chela te 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 arrangement. Compound 5a can be more easily prepared by treating the perchlorato complex [Mn(CO)₃(S₂CPCy₃)(OClO₃)] (2a) with NaBH₄. This procedure is general and can be used for the preparation of several derivatives containing either manganese or rhenium [M₂(CO)₆{μ-S₂C(H)PR₃} ₂] 5a-d. The reaction of cationic tricarbonyl complexes [M(CO)₃(S₂CPR₃)(PPh₃)]PF₆ (M = Mn, Re) with NaBH₄ produces the same dimers 5a or 5c by displacement of the PPh₃ ligand. Treatment of the dimer 5a with excess PEt₃ or P(OMe)₃ leads to the cleavage of the bridges and loss of one CO and the PR₃ group from the S₂C(H)PR₃ unit to afford ultimately the dithioformate complexes [Mn(CO)₂(S₂CH)(L)₂] [L = PEt₃, P(OMe)₃]. VCH Verlagsgesellschaft mbH, 1996.