Electronic and resonance-Raman spectra of mixed-valence ammine complexes of palladium and platinum

Abstract

The resonance-Raman spectra of the mixed-valence complexes [Pt(NH3)2Br2][Pt(NH3)2Br4], [Pd(NH3)2Br2][Pt(NH3)2Br4], [Pd(NH3)2Cl2][Pt(NH3)2Cl4], and [Pd(NH3)2Cl2][Pd(NH3)2Cl4] have been recorded at ca. 80 K and with a variety of different exciting lines. Assignments for the observed bands and progressions are given. Studies of the excitation profiles of key Raman bands of these complexes, in particular of the axial νsym(MX) and the non-axial νsym(MX) and νsym(MN) modes, have led to a systematic set of assignments for the lowest mixed-valence transitions of these complexes. These are: PtIVâ†�PtII at ⩽ 13 000 cm–1 in [Pt(NH3)2Br2][Pt(NH3)2Br4]; PtIVâ†�PdII at 16 000 cm–1 and PdIVâ†�PtII at ⩽ 13 000 cm–1 in [Pd(NH3)2Br2][Pt(NH3)2Br4]; PdIVâ†�PtII at ca. 18 000 cm–1 in [Pd(NH3)2Cl2][Pt(NH3)2Cl4]; and PdIVâ†�PdII at ca. 13 000 cm–1 in [Pd(NH3)2Cl2][Pd(NH3)2Cl4].