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 ν_sym(MX) and the non-axial ν_sym(MX) and ν_sym(MN) modes, have led to a systematic set of assignments for the lowest mixed-valence transitions of these complexes. These are: Pt^IVâ†�Pt^II at ⩽ 13 000 cm^–1 in [Pt(NH₃)₂Br₂][Pt(NH₃)₂Br₄]; Pt^IVâ†�Pd^II at 16 000 cm^–1 and Pd^IVâ†�Pt^II at ⩽ 13 000 cm^–1 in [Pd(NH₃)₂Br₂][Pt(NH₃)₂Br₄]; Pd^IVâ†�Pt^II at ca. 18 000 cm^–1 in [Pd(NH₃)₂Cl₂][Pt(NH₃)₂Cl₄]; and Pd^IVâ†�Pd^II at ca. 13 000 cm^–1 in [Pd(NH₃)₂Cl₂][Pd(NH₃)₂Cl₄].