Rhenium trioxide
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Names | |||
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IUPAC name
Rhenium trioxide
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Other names
Rhenia
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Identifiers | |||
3D model (JSmol)
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ECHA InfoCard | 100.013.845 | ||
EC Number |
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PubChem CID
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UNII | |||
CompTox Dashboard (EPA)
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Properties | |||
ReO3 | |||
Molar mass | 234.205 g/mol | ||
Appearance | Deep red crystals | ||
Density | 6.92 g/cm3 | ||
Melting point | 400 °C (752 °F; 673 K) (decomposes) | ||
+16.0·10−6 cm3/mol | |||
Refractive index (nD)
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1.68 | ||
Structure | |||
Cubic, cP4 | |||
Pm3m, No. 221 | |||
a = 374.8 pm
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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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Rhenium trioxide or rhenium(VI) oxide is an inorganic compound with the formula ReO3. It is a red solid with a metallic lustre that resembles copper in appearance. It is the only stable trioxide of the Group 7 elements (Mn, Tc, Re).
Preparation and structure
[edit]Rhenium trioxide can be formed by reducing rhenium(VII) oxide with carbon monoxide at 200 °C or elemental rhenium at 400 °C.[1]
- Re2O7 + CO → 2 ReO3 + CO2
- 3 Re2O7 + Re → 7 ReO3
Re2O7 can also be reduced with dioxane.[2]
Rhenium trioxide crystallizes with a primitive cubic unit cell, with a lattice parameter of 3.742 Å (374.2 pm). The structure of ReO3 is similar to that of perovskite (ABO3), without the large A cation at the centre of the unit cell. Each rhenium center is surrounded by an octahedron defined by six oxygen centers. These octahedra share corners to form the 3-dimensional structure. The coordination number of O is 2, because each oxygen atom has 2 neighbouring Re atoms.[3]
Properties
[edit]Physical properties
[edit]ReO3 is unusual for an oxide because it exhibits very low resistivity. It behaves like a metal in that its resistivity decreases as its temperature decreases. At 300 K, its resistivity is 100.0 n
Chemical properties
[edit]Rhenium trioxide is insoluble in water, as well as dilute acids and bases. Heating it in base results in disproportionation to give ReO
2 and ReO−
4, while reaction with acid at high temperature affords Re
2O
7. In concentrated nitric acid, it yields perrhenic acid.
Upon heating to 400 °C under vacuum, it undergoes disproportionation:[2]
- 3 ReO3 → Re2O7 + ReO2
Rhenium trioxide can be chlorinated to give rhenium trioxide chloride:[4]
- 2 ReO3 + Cl2 → 2 ReO3Cl
Uses
[edit]Hydrogenation catalyst
[edit]Rhenium trioxide finds some use in organic synthesis as a catalyst for amide reduction.[5]
References
[edit]- ^ H. Nechamkin, C. F. Hiskey, "Rhenium(VI): Oxide (Rhenium Trioxide)" Inorganic Syntheses, 1950 Volume 3, pp. 186-188. doi:10.1002/9780470132340.ch49
- ^ a b O. Glemser; R. Sauer (1963). "Rhenium(VI) Oxide". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2pages=1482. NY, NY: Academic Press.
- ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8., p. 1047.
- ^ O. Glemser; R. Sauer (1963). "Rhenium (VII) Oxychloride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2pages=1480. NY, NY: Academic Press.
- ^ Nishimura, Shigeo (2001). Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis (1st ed.). New York: Wiley-Interscience. p. 408. ISBN 9780471396987.