Electronic and resonance Raman spectra of [Au2(CS3)2]2-. Spectroscopic properties of a 'short' Au(I)-Au(I) bond

Abstract

The anion [Au 2(CS 3) 2] 2- has an unusually short Au-Au distance (2.80 Å) for a binuclear Au(I) complex. We report detailed Raman studies of the (n)Bu 4N + salt of this complex, including FT-Raman of the solid and UV/vis resonance Raman of dimethyl sulfoxide solutions. All five totally symmetric vibrations of the anion have been located and assigned. A band at Δv = 125 cm -1 is assigned to v(Au 2). The visible-region electronic absorption bands (384 (ε 30680) and 472 nm (ε 610 M -1 cm -1)) are attributable to CS 3 2- localized transitions, as confirmed by the dominance of v(sym)(C-S(exo)) (Δv = 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(dσ* → pσ) transition, largely because v(sym)(C-S(exo)) is not strongly enhanced in RR involving this band. Observation of the expected strong resonance enhancement of v(Au 2) was precluded as a result of masking by intense solvent Rayleigh scattering in the UV.