Potassium osmate

Potassium osmate
Names
	Other names Potassium osmate(VI) dihydrate
Identifiers
CAS Number	10022-66-9;
3D model (JSmol)	Interactive image;
ECHA InfoCard	100.157.189
UNII	5M2BWQ2TYJ ;
CompTox Dashboard (EPA)	DTXSID80693853 ;
	InChI InChI=1S/2K.4H2O.2O.Os/h;;41H2;;;/q2+1;;;;;2*-1;+4/p-4 Key: DDTIHYGDUUGVNU-UHFFFAOYSA-J;
	SMILES [K+].[K+].[O-][Os](O)(O)(O)(O)[O-];
Properties
Chemical formula	H4K2O6Os
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]. This diamagnetic purple salt contains osmium in the VI (6+) oxidation state.[1] When dissolved in water a pink solution is formed but when dissolved in methanol, the salt gives a blue solution.[1] The salt gained attention as a catalyst for the asymmetric dihydroxylation of olefins.[2]

Structure

The complex anion is octahedral. Like related d² dioxo 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.

Preparation

The compound was first reported by Edmond Frémy in 1844.[4]

Potassium osmate is prepared by reducing perosmates using alcohol:[5]

2 OsO₄ + C₂H₅OH + 3 KOH → CH₃CO₂K + 2 K₂[OsO₂(OH)₄]

Alkaline oxidative fusion of osmium metal also affords this salt.[1]

References

F. Albert Cotton; Geoffrey Wilkinson (1966). Advanced Inorganic Chemistry: A Comprehensive Treatise. p. 1007.
Li, Guigen; Chang, Han-Ting; Sharpless, K. Barry (1996). "Catalytic Asymmetric Aminohydroxylation (AA) of Olefins". Angew. Chem. Int. Ed. Engl. 35: 451–4. doi:10.1002/anie.199604511.CS1 maint: uses authors parameter (link)
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. doi:10.1524/ncrs.2002.217.jg.303
Frémy, E. "Ueber das Osmium" Journal für Praktische Chemie 1844 vol.33, 406-416. doi: 10.1002/prac.18440330160
John M. Malin (1980). "Potassium Tetrahydroxodioxoosmate(VI) and trans-Bis(Ethylenediamine)Dioxoosmium(VI) Chloride". Inorganic Syntheses. 20: 61–63. doi:10.1002/9780470132517.ch18.

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[candw-1] F. Albert Cotton; Geoffrey Wilkinson (1966). Advanced Inorganic Chemistry: A Comprehensive Treatise. p. 1007.

[2] Li, Guigen; Chang, Han-Ting; Sharpless, K. Barry (1996). "Catalytic Asymmetric Aminohydroxylation (AA) of Olefins". Angew. Chem. Int. Ed. Engl. 35: 451–4. doi:10.1002/anie.199604511.CS1 maint: uses authors parameter (link)

[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. doi:10.1524/ncrs.2002.217.jg.303

[4] Frémy, E. "Ueber das Osmium" Journal für Praktische Chemie 1844 vol.33, 406-416. doi: 10.1002/prac.18440330160

[5] John M. Malin (1980). "Potassium Tetrahydroxodioxoosmate(VI) and trans-Bis(Ethylenediamine)Dioxoosmium(VI) Chloride". Inorganic Syntheses. 20: 61–63. doi:10.1002/9780470132517.ch18.