SYNTHESIS, STRUCTURE, VIBRATIONAL-SPECTRA AND CHEMICAL-PROPERTIES OF THE TRIANGULAR MOLYBDENUM AND TUNGSTEN COMPLEXES M3(MU-3-S)(MU-2-SSE)3X62 (M = MO, W, X = CL, BR)

Salts containing M3(μ3-S)(μ2-S2)3X62- (M = Mo, W; X = Cl, Br) anions interact with SePPh3 upon heating in acetonitrile to form SPPh3 and M3(μ3-S)(μ2-SSe)3X62-. The stereochemisty of this reaction has been studied. In the reaction of SePPh3 with Mo3(μ3-34S)(μ2-34Sa32Se)3X62- replacement of the equatorial sulfur atoms takes place, and 32SPPh3 and Mo3(μ3-34S)(μ2-34SaSee)3X62- are produced. The structure of (PPh3Et)2Mo3(μ3-S)(μ2-SSe)3Cl6 (I) was established by X-ray diffraction analysis. The crystals of I are triclinic, space group P1 (a = 13.547(2), b = 13.755(2), c = 15.736(3) Å; α = 101.79(1), β = 97.71(1), γ = 110.49(1)°, Z = 2). A total of 5721 independent reflections has been collected on an automated diffractometer, and the structure was solved to R = 0.051 (Rw = 0.062). The selenium atoms are essentially in the plane of the Mo3 triangle. The SSe distances are 2.157(5)-2.163(4) Å. Complex I is the first compound containing a SSe ligand that has been structurally characterized. IR and Raman spectra of M3S4Se3X62- have been studied. For Mo3S4Se3Cl62- an analysis of the normal vibrations has been performed. The force constant of the SSe bond in complex I is 2.3 mdyn/ Å. Heating of (Et4N)2Mo3S4Se3Br6 under vacuum at 450 °C gave rise to MoSSe. © 1990.