Osmium dioxide

Osmium dioxide

Names
IUPAC name Osmium dioxide
Other names Osmium(IV) oxide
Identifiers
CAS Number	12036-02-1
PubChem	187574
Properties
Chemical formula	OsO2
Molar mass	222.229 g/mol
Appearance	black or yellow brown
Density	11.4 g/cm^3
Melting point	500 °C (932 °F; 773 K) (decomposes)
Related compounds[1]
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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Infobox references

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.

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.^[2][3] Using chemical transport, one can obtain large crystals of OsO₂, sized up to 7x5x3 mm³. Single crystals show metallic resistivity of ~15 μΩ cm. Typical transport agent is O
2 via the reversibly formation of volatile OsO₄:^[4]

OsO₂ + O₂ OsO₄

Reactions

OsO₂ does not dissolve in water but is attacked by dilute hydrochloric acid.^[5][6] The crystals have rutile structure.^[7] Unlike osmium tetroxide, OsO₂ is not toxic.^[8]

References

1. OsO₂ at webelements
2. A. F. Holleman and E. Wiberg (2001). Inorganic chemistry. Academic Press. p. 1465. ISBN 0-12-352651-5.
3. 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.
4. Rogers, D. B.; Butler, S. R.; Shannon, R. D. (1972). "Single Crystals of Transition-Metal Dioxides". Inorganic Syntheses XIV: 135–145. doi:10.1002/9780470132449.ch27.
5. 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.
6. 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.
7. 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.
8. Smith, I.C., B.L. Carson, and T.L. Ferguson (1974). "Osmium: An appraisal of environmental exposure.". Env Health Perspect (Brogan &#38) 8: 201–213. doi:10.2307/3428200. JSTOR 3428200. PMC 1474945. PMID 4470919.