Potassium osmate
Potassium osmate is the inorganic compound with the formula K2. This diamagnetic purple salt contains osmium in the VI oxidation state. When dissolved in water a pink solution is formed but when dissolved in methanol, the salt gives a blue solution. The salt gained attention as a catalyst for the asymmetric dihydroxylation of olefins.Structure
The complex anion is octahedral. Like related d2 dioxo complexes, the oxo ligands are trans. The Os=O and Os-OH distances are 1.75 and 1.99 Å, respectively. It is a relatively rare example of a metal oxo complex that obeys the 18e rule.Preparation
The compound was first reported by Edmond Frémy in 1844.
Potassium osmate is prepared by reducing perosmates using alcohol:
Alkaline oxidative fusion of osmium metal also affords this salt.
