Electronic and resonance Raman spectra of [Au-2(CS3)(2)](2-). Spectroscopic properties of a "short" An(I)-Au(I) bond

The anion [Au-2(CS3)(2)](2-) has an unusually short Au-Au distance (2.80 An gstrom) for a binuclear Au(I) complex. We report detailed Raman studies of the (Bu4N+)-Bu-n Salt of this complex, including FT-Raman of the solid and UV/vis resonance Raman of dimethyl sulfoxide solutions. All five totally sy mmetric vibrations of the anion have been located and assigned. A band at D elta nu = 125 cm(-1) is assigned to nu(Au-2). The visible-region electronic absorption bands (384 (epsilon 30 680) and 472 nm (epsilon 610 M-1 cm(-1)) ) are attributable to CS32- localized transitions, as confirmed by the domi nance of nu(sym)(C-S-exo) (Delta nu = 951 cm(-1)) in RR spectra measured in this region. An absorption band at 314 nm (22 250 M-1 cm(-1)) is assigned as the metal-metal (1)(do* --> p sigma) transition, largely because nu(sym) (C-S-exo) is not strongly enhanced in RR involving this band. Observation o f the expected strong resonance enhancement of nu(Au-2) was precluded as a result of masking by intense solvent Rayleigh scattering in the UV.