Nature of the cherry-red transient formed during the interaction of osmium tetroxide with hydrogen peroxide

Summary

A cherry-red transitory coloration is formed when OsO₄ or osmium(VI) is added to alkaline hydrogen peroxide solution in the pH range 9–13. The transient has an absorption maximum at 530 nm and its concentration depends on the pH of reaction mixture reaching a maximum at pH 10.5–11. The transient is designated as a peroxo-derivative of osmium(VIII) [or an osmium(VII) — Superoxide radical pair if the peroxoderivative undergoes a fast intramolecular one-electron transfer].

Many decades ago it was observed¹ that a cherry-red coloration appears transiently when osmium tetroxide solution is added to alkaline hydrogen peroxide solution. However, to our knowledge, there are no literature data about the nature of this transient. Further, we observed recently that there is a close connection between the rate of decomposition of hydrogen peroxide catalysed by osmium tetroxide and the intensity of the coloration, and therefore an attempt was made to investigate the transient by using a fast spectrophotometer technique.