Rhenium(VII) oxide


Rhenium oxide is the inorganic compound with the formula Re2O7. This yellowish solid is the anhydride of HOReO3. Perrhenic acid, Re2O7·2H2O, is closely related to Re2O7. Re2O7 is the raw material for all rhenium compounds, being the volatile fraction obtained upon roasting the host ore.

Structure

Crystalline Re2O7 is an inorganic polymer, which consists of alternating octahedral and tetrahedral Re centres. Upon heating, the polymer cracks to give molecular Re2O7. This molecular species closely resembles manganese heptoxide, consisting of a pair of ReO4 tetrahedra that share a vertex, i.e., O3Re-O-ReO3.

Synthesis and reactions

Rhenium oxide is formed when metallic rhenium or its oxides or sulfides are oxidized at 500-700 °C in air.:
Re2O7 is very reactive toward water. It dissolves in water to give perrhenic acid. It is a precursor to methylrhenium trioxide, a catalyst for oxidations.

Uses

Hydrogenation catalyst

Rhenium oxide finds some use in organic synthesis as a catalyst for ethenolysis, carbonyl reduction and amide reduction.