Vibrational interactions in dimethylgold(III) halides and carboxylates

The far-infrared and Raman spectra of binuclear molecules [Me2AuX]2 (X = Cl, Br, I) and [Me2Au(OOCR)]2 (R = Me, CF3, But, Ph) in the 600-70 cm−1 region are reported. The experimentally measured vibrational frequencies of [Me2AuX]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 [Me2AuX]2 far-IR and Raman spectra have been observed. The Raman-active Au…Au vibrations of the [Me2Au(OOCR)]2 molecules were found to be in the same region as those of [Me2AuX]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 [Me2AuX]2 increase in the sequence I < Br < Cl while the AuC2 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 [Me2AuX]2 and [Me2Au(OOCR)]2 compounds have been found between 600 and 500 cm−1.