Potassium osmate

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Potassium osmate
Other names
Potassium osmate(VI) dihydrate
Molar mass 368.42
Appearance purple solid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium osmate is the inorganic compound with the formula K2[OsO2(OH)4]. It contains Osmium in the VI (6+) oxidation state. It is a diamagnetic purple salt that gained attention as a catalyst for the asymmetric dihydroxylation of olefins.[1] When dissolved in water a pink solution is formed.[2] But when dissolved in methanol the solution is blue.[2]

Like related d2 complexes, the oxo ligands are trans.[3] The Os=O and Os-OH distances are 1.75(2) and 1.99(2) Å, respectively. It is a relatively rare example of a metal oxo complex that obeys the 18e rule. The compound was first reported by Edmond Frémy in 1844.[4]

Osmate salts can be produced by reducing perosmates using alcohol. Osmium tetroxide is dissolved in potassium hydroxide water solution to produce K2[OsO4(OH)2], which is then reduced to potassium osmate.[2] Another way to make this is by alkaline oxidative fusion of osmium metal.[2]


  1. ^ Li, Guigen; Chang, Han-Ting; Sharpless, K. Barry "Catalytic asymmetric aminohydroxylation (AA) of olefins" Angew. Chem. Int. Ed. Engl. 1996, volume 35, pp. 451-4. doi:10.1002/anie.199604511
  2. ^ a b c d F. Albert Cotton; Geoffrey Wilkinson (1966). Advanced Inorganic Chemistry: A Comprehensive Treatise. p. 1007. 
  3. ^ R. K. Murmann, C. L. Barnes "Redetermination of the crystal structure of potassium trans-(dioxo)-tetra(hydroxo)osmate(VI), K2[Os(OH)4(O)2]" Z. Kristallogr. NCS 217, 2002, pp. 303–304.
  4. ^ Frémy, E. "Ueber das Osmium" J. Prakt. Chem. 1844 vol.33, 406-416. doi: 10.1002/prac.18440330160