Vibrational interactions in dimethylgold(III) halides and carboxylates

Abstract

The far-infrared and Raman spectra of binuclear molecules [Me 2AuX] 2 (X = Cl, Br, I) and [Me 2Au(OOCR)] 2 (R = Me, CF 3, Bu t, Ph) in the 600–70 cm −1 region are reported. The experimentally measured vibrational frequencies of [Me 2AuX] 2 are in a good agreement with density functional theory predictions. The Au…Au vibrational interactions predicted to be in the 270–60 cm −1 region of [Me 2AuX] 2 far-IR and Raman spectra have been observed. The Raman-active Au…Au vibrations of the [Me 2Au(OOCR)] 2 molecules were found to be in the same region as those of [Me 2AuX] 2. The Au–X stretching modes were observed between 100 and 250 cm −1 in accordance with the DFT predictions. Their frequencies in the IR spectra of [Me 2AuX] 2 increase in the sequence I < Br < Cl while the AuC 2 stretching frequencies decrease in the same order. This fact might be an evidence of the decreasing covalent character of the gold-halogen bridges. The Au–O stretching bands of dimethylgold(III) carboxylates have been observed in the 500–250 cm −1 region, and Au–C stretching frequencies of both [Me 2AuX] 2 and [Me 2Au(OOCR)] 2 compounds have been found between 600 and 500 cm −1.