A vibrational study of various KAuCl4-xBrx solid solutions

Infrared and Raman vibrational studies have been undertaken on various powd ered KAuCl4-xBrx (0 less than or equal to x less than or equal to 4) solid solutions. Characteristic variations of the spectra clearly demonstrate the existence of distinct individual planar anions. From a comparison of the v ibrational data with results of valence force field calculations, we are ab le to discuss the domains of existence of several anions and to characteris e with confidence the following halide mixed species: The(AuCl3Br)(-) anion is characterised in Infrared by four stretching (at 3 54, 343, 330 and 236 cm(-1)) and three deformation bands (at 196, 178 and 1 48 cm(-1)) and in Raman by essentially the intense line at 236 cm(-1) (v Au -Br). The (AuCl2Br2)(-) 'trans' displays intense infrared (at 357 and 254 cm(-1)) and Raman (at 340 and 203 cm(-1)) stretching bands. The(AuClBr3)(-) anion exhibits three stretching Raman modes (at 236, 212 an d 203 cm(-1)) and one stretching (at 336 cm(-1)) plus three bending Infrare d modes (at 178, 134 and 118 cm(-1)). Furthermore, from intensity variations of the Raman lines at 203 and 236 cm (-1), it is evidenced that the 236 cm(-1) signal is mainly due at low 'x' c oncentration to the only (AuCl3Br)(-) entity, but at higher 'x' values (x > 30%) to at least two species, including perhaps the (AuCl2Br2)(-) 'cis' an ion. (C) 1999 Elsevier Science B.V. All rights reserved.