Rhenium trioxide or rhenium(VI) oxide is an inorganic compound with the formula ReO3. It is a red solid with a metallic lustre, which resembles copper in appearance. It is the only stable trioxide of the Group 7 elements (Mn, Tc, Re).
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||234.205 g/mol|
|Appearance||Deep red crystals|
|Melting point||400 °C (752 °F; 673 K) (decomposes)|
Refractive index (nD)
|Pm3m, No. 221|
a = 374.8 pm
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Preparation and structureEdit
- Re2O7 + CO → 2 ReO3 + CO2
- 3 Re2O7 + Re → 7 ReO3
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.
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 nΩ·m, whereas at 100 K, this decreases to 6.0 nΩ·m, 17 times less than at 300 K.
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
7. In concentrated nitric acid, it yields perrhenic acid. Upon heating to 400 °C under vacuum, it undergoes disproportionation:
- 3 ReO3 → Re2O7 + ReO2
- H. Nechamkin, C. F. Hiskey, "Rhenium(VI): Oxide (Rhenium Trioxide)" Inorganic Syntheses, 1950 Volume 3, pp. 186-188. doi:10.1002/9780470132340.ch49
- G. Glemser "Rhenium (VI) Oxide" Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 2. p. 1482.
- Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8., p. 1047.
- Nishimura, Shigeo (2001). Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis (1st ed.). New York: Wiley-Interscience. p. 408. ISBN 9780471396987.