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–Pt^IV–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.