Osmium dioxide

Preparation

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. Using chemical transport, one can obtain large crystals of , sized up to 7x5x3 mm3. Single crystals show metallic resistivity of ~15 μΩ cm. A typical transport agent is via the reversible formation of volatile : :

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. : + → •2 + 2KOH +

Adding strong alkali to chloroosmic acid or its salts also yields the dihydrate. : + 4KOH → 6KCl + •2

Properties

Osmium dioxide does not dissolve in water, but it can be dissolved by strong acids such as hydrochloric acid. The crystals have rutile structure.{{cite journal|journal = Acta Chemica Scandinavica | year = 1970 |volume = 24 | pages = 123–128|title = Precision Determination of the Crystal Structure of Osmium Dioxide| author = Boman C.E.|doi = 10.3891/acta.chem.scand.24-0123|last2 = Danielsen|first2 = Jacob|last3 = Haaland|first3 = Arne|author3-link=Arne Haaland|last4 = Jerslev|first4 = Bodil|last5 = Schäffer|first5 = Claus Erik|last6 = Sunde|first6 = Erling|last7 = Sørensen|first7 = Nils Andreas |doi-access = free}} Unlike osmium tetroxide, is not toxic.

Hexavalent osmium

Compounds of osmium in the +6 oxidation state are dominated by the osmyl species, in which 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.

Examples of osmyl compounds include , , and , but many others are known.

References

References

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12. McFadzean, Belinda. (December 2007). "The Kinetics and Associated Equilibra of High Oxidation State Osmium Complexes". Nelson Mandela Metropolitan University.