This diamagnetic purple salt contains osmium in the VI (6+) oxidation state.

[1] The salt gained attention as a catalyst for the asymmetric dihydroxylation of olefins.

Like related d2 dioxo complexes, the oxo ligands are trans.

It is a relatively rare example of a metal oxo complex that obeys the 18e rule.

[4] Potassium osmate is prepared by reducing osmium tetroxide with ethanol:[5] Alkaline oxidative fusion of osmium metal also affords this salt.