Osmium dioxide

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Osmium dioxide
Osmium(IV) oxide Rutile-unit-cell-3D-balls.png
Osmium(IV) oxide
OsO2 dihydrate.jpg
Osmium dioxide dihydrate
Names
IUPAC name
Osmium dioxide
Other names
Osmium(IV) oxide
Identifiers
3D model (JSmol)
ChemSpider
PubChem CID
  • InChI=1S/2O.Os
    Key: XSXHWVKGUXMUQE-UHFFFAOYSA-N
  • O=[Os]=O
Properties
OsO2
Molar mass 222.229 g/mol
Appearanceblack or yellow brown
Density 11.4 g/cm3
Melting point 500 °C (932 °F; 773 K) (decomposes)
insoluble [1]
Solubility dissolves in HCl
Related compounds [2]
Related osmium oxides
Osmium tetroxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Osmium dioxide is an inorganic compound with the formula OsO2. It exists as brown to black crystalline powder, but single crystals are golden and exhibit metallic conductivity. The compound crystallizes in the rutile structural motif, i.e. the connectivity is very similar to that in the mineral rutile.

Contents

Preparation

OsO2 can be obtained by the reaction of osmium with a variety of oxidizing agents, including, sodium chlorate, osmium tetroxide, and nitric oxide at about 600 °C. [3] [4] Using chemical transport, one can obtain large crystals of OsO2, sized up to 7x5x3 mm3. Single crystals show metallic resistivity of ~15 μΩ cm. A typical transport agent is O
2 via the reversible formation of volatile OsO4: [5]

OsO2 + O2 ⇌ OsO4

It can also be prepared by reducing osmium in higher oxidation states with alcohol, in which it forms a dihydrate. As opposed to the anhydrous dioxide, the dihydrate possesses a bluish black appearance. [6] [7]

K2[OsO2(OH)4] + C2H5OH → OsO2•2H2O + 2KOH + CH3CHO

Adding strong alkali to chloroosmic acid or its salts also yields the dihydrate. [6] [7] [8]

K2OsCl6 + 4KOH → 6KCl + OsO2•2H2O

Properties

Osmium dioxide does not dissolve in water, but it can be dissolved by strong acids such as hydrochloric acid. [9] [10] The crystals have rutile structure. [11] Unlike osmium tetroxide, OsO2 is not toxic. [12]

Hexavalent osmium

Compounds of osmium in the +6 oxidation state are dominated by the osmyl species, in which OsO2 exists as a radical trans-dioxo moiety. These osmyl compounds are all diamagnetic, and stabilized by strong σ-donor and π-donor ligands. Most osmyl compounds are mononuclear and have a linear O=Os=O structure. [6] [13]

Examples of osmyl compounds include K2[OsO2(OH)4] and [OsO2(NH3)4]Cl2 , but many others are known.

References

  1. ↑ Comey, Arthur Messinger (1896). A Dictionary of Chemical Solubilities: Inorganic. Macmillan and Company. p. 275. Retrieved 3 July 2025.
  2. ↑ OsO2 at webelements
  3. ↑ A. F. Holleman & E. Wiberg (2001). Inorganic chemistry. Academic Press. p. 1465. ISBN   0-12-352651-5.
  4. ↑ Thiele G.; Woditsch P. (1969). "Neutronenbeugungsuntersuchungen am Osmium(IV)-oxid". Journal of the Less Common Metals. 17 (4): 459. doi:10.1016/0022-5088(69)90074-5.
  5. ↑ Rogers, D. B.; Butler, S. R.; Shannon, R. D. (1972). "Single Crystals of Transition-Metal Dioxides". Inorganic Syntheses. Vol. XIII. pp. 135–145. doi:10.1002/9780470132449.ch27. ISBN   9780470132449.
  6. 1 2 3 J. Newton Friend (1920). "Osmium and its compounds". A textbook of inorganic chemistry, vol.IX Part I Cobalt, Nickel, and The Elements of The Platinum Group (PDF). London: Charles Griffin and Company, Limited. pp. 12, 216–219, 222. Retrieved 3 July 2025.
  7. 1 2 Prakash Satya (2013). "Platinum Metals-IV:Osmium". Advanced Chemistry of Rare Elements, 5th Ed. India: S Chand and Company Limited. p. 611. Retrieved 24 July 2025.
  8. ↑ Stopinski, Orin (September 1977). "Platinum-Group Metals" (PDF). Environmental Health Effects Research Series. Washington, DC: Environmental Protection Agency: 85–86. Retrieved 3 July 2025.
  9. ↑ J. E. Greedan; D. B. Willson; T. E. Haas (1968). "Metallic nature of osmium dioxide". Inorg. Chem. 7 (11): 2461–2463. doi:10.1021/ic50069a059.
  10. ↑ Yen, P (2004). "Growth and characterization of OsO
    2     single crystals". Journal of Crystal Growth. 262 (1–4): 271. doi:10.1016/j.jcrysgro.2003.10.021.
  11. ↑ Boman C.E.; Danielsen, Jacob; Haaland, Arne; Jerslev, Bodil; Schäffer, Claus Erik; Sunde, Erling; Sørensen, Nils Andreas (1970). "Precision Determination of the Crystal Structure of Osmium Dioxide". Acta Chemica Scandinavica. 24: 123–128. doi: 10.3891/acta.chem.scand.24-0123 .
  12. ↑ Smith, I.C., B.L. Carson, and T.L. Ferguson (1974). "Osmium: An appraisal of environmental exposure". Env Health Perspect. 8. National Institute of Environmental Health Sciences: 201–213. doi:10.2307/3428200. JSTOR   3428200. PMC   1474945 . PMID   4470919.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  13. ↑ McFadzean, Belinda (December 2007). The Kinetics and Associated Equilibra of High Oxidation State Osmium Complexes (PDF) (PhD thesis). Port Elizabeth, South Africa: Nelson Mandela Metropolitan University. Retrieved 3 July 2025.
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