Resonance Raman spectra of some mixed-valence halogeno-compounds of antimony and lead

Abstract

Resonance-Raman (r.r.) spectra are reported for a series of mixed-valence compounds of antimony. With Cs₂[SbCl₆]· Rb₂[SbCl₆], or Cs₄[SbBiCl₁₂], several overtone and combination tone progressions, in which the progressing fundamental is ν₁(a_1g) of the [SbCl₆]^– ion, have been observed on irradiation within the contour of the mixed-valence charge-transfer transition. The results are interpreted in terms of dimensional changes accompanying the transition. In view of the conflicting reports in the literature, the assignment of the Raman-active fundamental vibrations of the [SbCl₆]^3– ion is discussed in the light of the r.r. results. Weak r.r. effects have also been observed for two related mixed-valence compounds of lead of composition M^III[PbCl₆].