Platinum(IV) Superoxo Complexes
Platinum(IV) Superoxo Complexes. Kiselev Yu.M., Pankratov D.A., Ezerskaya N.A., Kiseleva I.N., Shundrin L.A., Popovich M.P. //Russian Journal of Inorganic Chemistry. 1994. V.39. №8. P. 1278-1283
The products of reaction of platinum(IV) hydroxo complexes with ozone in alkaline solutions were studied using various physicochemical methods: electronic spectroscopy, electron spin resonance, and cyclic voltammetry. The arguments presented suggest that the blue solutions obtained contain superoxo Pt(IV) complexes.
One of the most efficient ways to stabilize higher oxidation states in the transition elements is complex formation in aqueous-alkaline media. In this case, hydroxyl ions offer advantages over other ligands and produce a stronger decrease in E° of a redox system than other, rather weakly polarizable ligands, which form complex ions in acid and neutral media. This circum stance is the one favoring stabilization of the highest oxidation states in neptunium, plutonium, americium(VII), and iron(VIII).
Hence, in alkaline media, heavy d transition metals, platinum especially, are expected to form rather stable compounds containing elements in their highest oxidation states (e.g., oxo or hydroxo complexes). Obtaining these elements in their highest oxidation states is still a problem.
In this connection, we attempted to oxidize platinum(IV) hydroxo complexes with ozone in alkaline medium, and observed the formation of intensely blue solutions.
This paper aims at investigation of the compounds thus prepared in order to establish the composition and geometry of the blue complexes.
Thus, the body of the data available makes it possible to state that ozonization of the hexahydroxo platinates(IV) produces platinum(IV) complexes with superoxo ligands. These complexes are rather unstable entities generating oxygen upon their decomposition.