Rhenium(VII) oxide is the

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula Re₂ O₇. This yellowish solid is the

anhydride An acid anhydride is a type of chemical compound derived by the removal of water molecules from an acid (chemistry), acid. In organic chemistry, organic acid anhydrides contain the functional group . Organic acid anhydrides often form when one ...

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

Solid Re₂O₇ consists of alternating octahedral and tetrahedral Re centres. Upon heating, the polymer cracks to give molecular (nonpolymeric) Re₂O₇. This molecular species closely resembles

manganese heptoxide Manganese(VII) oxide (manganese heptoxide) is an inorganic compound with the formula . Manganese heptoxide is a volatile liquid with an oily consistency. It is a highly reactive and powerful oxidizer that reacts explosively with nearly any organi ...

, consisting of a pair of ReO₄ tetrahedra that share a vertex, i.e., O₃Re–O–ReO₃.

Synthesis and reactions

Rhenium(VII) oxide is formed when metallic rhenium or its oxides or sulfides are oxidized at in air. Re₂O₇ dissolves in water to give perrhenic acid. Heating Re₂O₇ gives rhenium dioxide, a reaction signalled by the appearance of the dark blue coloration: :2Re₂O₇ → 4ReO₂ + 3O₂ Using

tetramethyltin Tetramethyltin is an organometallic compound with the formula (CH3)4Sn. This liquid, one of the simplest organotin compounds, is useful for transition-metal mediated conversion of acid chlorides to methyl ketones and aryl halides to aryl methyl k ...

, it converts to methylrhenium trioxide ("MTO"), a catalyst for oxidations: :Re₂O₇ + 2Sn(CH₃)₄ → CH₃ReO₃ + (CH₃)₃SnOReO₃ In a related reaction, it reacts with

hexamethyldisiloxane Hexamethyldisiloxane (HMDSO or MM) is an organosilicon compound with the formula O i(CH3)3. This volatile colourless liquid is used as a solvent and as a reagent in organic synthesis. It is prepared by the hydrolysis of trimethylsilyl chlori ...

to give the

siloxide Siloxides are chemical compounds with the formula R3SiOM, where R is usually an organic group and M is usually a metal cation. Also called silanolates, they are derived by deprotonation of Silanol, silanols. They also arise by the degradation of ...

: :Re₂O₇ + 2O(Si(CH₃)₃)₂ → 2(CH₃)₃SiOReO₃

Uses

Hydrogenation catalyst

Rhenium(VII) oxide finds some use in

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

as a

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

for ethenolysis, carbonyl reduction and amide reduction.

References

{{Oxides Rhenium compounds Acidic oxides Hydrogenation catalysts