Electronic, infrared, and resonance-Raman spectra of mixed-valence iodide-bridged linear-chain complexes of platinum

Abstract

Electronic, i.r., and resonance-Raman (r.R.) spectra of mixed-valence complexes of platinum, [Pt(en)I2][Pt(en)I4], [Pt(en)2][Pt(en)2I2][ClO4]4, and cis-[Pt(NH3)2(SCN)2][Pt(NH3)2(SCN)2I2], where en = 1,2-diaminoethane, have been recorded as powders or discs at ca. 80 K. In addition, a single-crystal polarized r.R. spectrum of [Pt(en)2][Pt(en)2I2][ClO4]4 at room temperature has been obtained. Under r.R. conditions, progressions in ν1(120–123 cm–1), the symmetric X–PtIV–X stretching mode of the quadrivalent constituent, reach to 7, 9, and 8 members, respectively. The results confirm in the first two cases, and demonstrate in the last case, that the complexes are linear-chain iodide-bridged species. Brief results are also given on K4[PtI4][PtI6]. The excitation profiles of ν1 and 2ν1 of [Pt(en)I2][Pt(en)I4] and [Pt(en)2][Pt(en)2I2][ClO4]4 all maximize near to, but on the low-wavenumber side of, the intervalence band maximum. Those of ν1 and 2ν1 of the thiocyanate complex display a double maximum for which no explanation can be advanced.