The inter-conversions of platinumcarbonyl dianionic clusters, [Pt3(CO)6]n2− (n = 2–5), in THF and acetonitrile. A combined in situFTIR spectroscopic and BTEM study leading to the characterization of the new [H4−xPt15(CO)19]x− (x = 2–4) clusters

Abstract

The inter-conversions of platinum carbonyl dianionic clusters, ([Pt₃(CO)₆]_n²⁻, n = 2–5), have been studied in THF and acetonitrile using in situ FTIR spectroscopy. These inter-conversions were facilitated by the addition (or removal) of molecular hydrogen. The individual reactions, namely reductions and oxidations of [Pt₃(CO)₆]_n²⁻ were fast and reversible. BTEM analysis of the data provided the pure component spectra of the individual species without the need for physical separation. It is shown, for the first time, that the species [Pt₃(CO)₆]_n²⁻ (n = 2) can be formed from the reduction of [Pt₃(CO)₆]_n²⁻ (n = 3–5) by hydrogen alone in acetonitrile. Also, detection of dissolved CO₂ in solution suggests that a room-temperature water gas shift reaction occurs. This has been shown to arise from nucleophilic attack of water on a coordinated CO of [Pt₃(CO)₆]_n²⁻ which leads to the formation of [HPt₁₅(CO)₁₉]³⁻ and [H₂Pt₁₅(CO)₁₉]²⁻. The parent tetraanion, [Pt₁₅(CO)₁₉]⁴⁻, has been isolated in high yields by reaction of [Pt₃(CO)₆]_n²⁻ (n = 2, 3) with NaOH at 60 °C and has been structurally characterized by X-ray analysis.