Rhenium trioxide

Rhenium trioxide
IUPAC name Rhenium trioxide
Other names Rhenia
Identifiers
CAS number	1314-28-9 Y
PubChem	102110
	EC number	215-228-8
Jmol-3D images	{{#if:O=[Re](=O)=O|Image 1
SMILES O=[Re](=O)=O
InChI InChI=1S/3O.Re
Properties
Molecular formula	ReO3
Molar mass	234.205 g/mol
Appearance	Deep red crystals
Density	6.92 g/cm3
Melting point	400 °C (decomposes)
Refractive index (nD)	1.68
Structure
Crystal structure	Cubic, cP4
Space group	Pm3m, SpaceGroup = 221
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

ReO₃ polyhedra

Rhenium trioxide or rhenium(VI) oxide is the inorganic compound with the formula ReO₃. It is a red solid with a metallic lustre. It is the only stable trioxide of the Group 7 elements (Mn, Tc, Re).

Structure

Rhenium oxide forms crystals with a primitive cubic unit cell, with a lattice parameter of 3.742 Å (374.2 pm). The structure of ReO₃ is similar to the Perovskite structure (ABO₃), without the large A cation at the centre of the unit cell. Each rhenium atom is surrounded by an octahedron of 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.^[1]

Properties

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.^[1]

Preparation

Rhenium trioxide can be formed by reducing rhenium(VII) oxide with carbon monoxide. ^[2]

Re₂O₇ + CO → 2 ReO₃ + CO₂

References