Ruthenium tetroxide
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Names | |||
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IUPAC name
Ruthenium(VIII) oxide
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Identifiers | |||
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ECHA InfoCard
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100.039.815 | ||
EC Number |
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UNII | |||
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Properties | |||
RuO4 | |||
Molar mass | 165.07 g/mol | ||
Appearance | yellow easily melting solid | ||
Odor | pungent | ||
Density | 3.29 g/cm3 | ||
Boiling point | 129.6[1] °C (265.3 °F; 402.8 K) | ||
2% w/v at 20 °C | |||
Solubility in other solvents | Soluble in Carbon tetrachloride Chloroform | ||
Structure | |||
tetrahedral | |||
zero | |||
Hazards | |||
NFPA 704 (fire diamond) | |||
Safety data sheet (SDS) | external MSDS sheet | ||
Related compounds | |||
Related compounds
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Ruthenium trichloride
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Ruthenium tetroxide is the
Preparation
RuO4 is prepared by oxidation of ruthenium(III) chloride with NaIO4.[2] The reaction initially produces sodium diperiododihydroxoruthenate(VI), which then decomposes in acid solution to the tetroxide:[5]
- 8 Ru3+(aq) + 5 IO4−(aq) + 12 H2O(l) → 8 RuO4(s) + 5 I−(aq) + 24 H+(aq)[6]
Due to its challenging reactivity, RuO4 it is always generated in situ and used in catalytic quantities, at least in organic reactions.[4]
Structure
RuO4 forms two crystal structures, one with cubic symmetry and another with monoclinic symmetry, isotypic to OsO4. The molecule adopts a tetrahedral geometry, with the Ru–O distances ranging from 169 to 170 pm.[7]
Uses
Isolation of ruthenium from ores
The main commercial value of RuO4 is as an intermediate in the production of ruthenium compounds and metal from ores. Like other
Organic chemistry
RuO4 is of specialized value in organic chemistry because it oxidizes virtually any hydrocarbon. For example, it will oxidize adamantane to 1-adamantanol. Because it is such an aggressive oxidant, reaction conditions must be mild, generally room temperature. Although a strong oxidant, RuO4 oxidations do not perturb stereocenters that are not oxidized. Illustrative is the oxidation of the following diol to a carboxylic acid:
Oxidation of epoxy alcohols also occurs without degradation of the epoxide ring:
Under milder conditions, oxidative reaction yields
Because RuO4 degrades the "double bonds" of arenes (especially electron-rich ones) by dihydroxylation and cleavage of the C-C bond in a way few other reagents can, it is useful as a "deprotection" reagent for carboxylic acids that are masked as aryl groups (typically phenyl or p-methoxyphenyl). Because the fragments formed are themselves readily oxidizable by RuO4, a substantial fraction of the arene carbon atoms undergo exhaustive oxidation to form carbon dioxide. Consequently, multiple equivalents of the terminal oxidant (often in excess of 10 equivalents per aryl ring) are required to achieve complete conversion to the carboxylic acid, limiting the practicality of the transformation.[11][12][13]
Although used as a direct
conditions, RuO4 is first activated by hydroxide, turning into the hyperruthenate anion:- RuO4 + OH− → HRuO5−
The reaction proceeds via a glycolate complex.
Other uses
Ruthenium tetroxide is a potential staining agent. It is used to expose latent fingerprints by turning to the brown/black ruthenium dioxide when in contact with fatty oils or fats contained in sebaceous contaminants of the print.[14]
Gaseous release by nuclear accidents
Because of the very high volatility of ruthenium tetroxide (RuO
4) ruthenium radioactive isotopes with their relative short half-life are considered as the second most hazardous gaseous isotopes after iodine-131 in case of release by a nuclear accident.[15][3][16] The two most important radioactive isotopes of ruthenium are 103Ru and 106Ru. They have half-lives of 39.6 days and 373.6 days, respectively.[3]
References
- .
- ^ a b H. L. Grube (1963). "Ruthenium (VIII) Oxide". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1. NY: Academic Press. pp. 1599–1600.
- ^ a b c Backman, U., Lipponen, M., Auvinen, A., Jokiniemi, J., & Zilliacus, R. (2004). Ruthenium behaviour in severe nuclear accident conditions. Final report (No. NKS–100). Nordisk Kernesikkerhedsforskning.
- ^ ISBN 978-0471936237.
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- ISSN 0022-3263.
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- S2CID 95804621.
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- ISSN 0022-3263.
- PMID 18179237.
- ISSN 0040-4020.
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- .
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Further reading
- Cotton, S.A. (1997). Chemistry of Precious Metals. London: Chapman and Hall. ISBN 978-0-7514-0413-5.
- Farmer, V.; Welton, T. (2002). "The oxidation of alcohols in substituted imidazolium ionic liquids using ruthenium catalysts". Green Chemistry. 4 (2): 97. doi:10.1039/B109851A.
- Singh, B.; Srivastava, S. (1991). "Kinetics and mechanism of ruthenium tetroxide catalysed oxidation of cyclic alcohols by bromate in a base". Transition Metal Chemistry. 16 (4): 466. S2CID 95711945.
- Courtney, J.L.; Swansbor, K.F. (1972). "Ruthenium tetroxide oxidation". Reviews of Pure and Applied Chemistry. 22: 47.