Rhenium(VII) oxide is the

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

with the formula Re₂ O₇. This yellowish solid is the

anhydride An organic acid anhydride is an acid anhydride that is an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the pa ...

of HOReO₃.

Perrhenic acid Perrhenic acid is the chemical compound with the formula . It is obtained by evaporating aqueous solutions of . Conventionally, perrhenic acid is considered to have the formula , and a species of this formula forms when rhenium(VII) oxide sublime ...

, 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, 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 Perrhenic acid is the chemical compound with the formula . It is obtained by evaporating aqueous solutions of . Conventionally, perrhenic acid is considered to have the formula , and a species of this formula forms when rhenium(VII) oxide sublime ...

. Heating Re₂O₇ gives rhenium dioxide, a reaction signalled by the appearance of the dark blue coloration:O. Glemser "Rhenium" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1476-85. :Re₂O₇ → 2ReO₂ + 1.5O₂ 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 ke ...

, it converts to

methylrhenium trioxide Methylrhenium trioxide, also known as methyltrioxorhenium(VII), is an organometallic compound with the formula CH3ReO3. It is a volatile, colourless solid that has been used as a catalyst in some laboratory experiments. In this compound, rhenium h ...

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

hexamethyldisiloxane Hexamethyldisiloxane (HMDSO) is an organosilicon compound with the formula O i(CH3)3sub>2. This volatile colourless liquid is used as a solvent and as a reagent in organic synthesis. It is prepared by the hydrolysis of trimethylsilyl chloride. ...

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 silanoates, they are derived by deprotonation of Silanol, silanols. They also arise by the degradation of S ...

: :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 special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

as a

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

for

ethenolysis In organic chemistry, ethenolysis is a chemical process in which internal olefins are degraded using ethylene () as the reagent. The reaction is an example of cross metathesis. The utility of the reaction is driven by the low cost of ethylene ...

carbonyl reduction In organic chemistry, carbonyl reduction is the organic reduction of any carbonyl group by a reducing agent. Typical carbonyl compounds are ketones, aldehydes, carboxylic acids, esters, and acid halides. Carboxylic acids, esters, and acid halides ...

and

amide reduction Amide reduction is a reaction in organic synthesis where an amide is reduced to either an amine or an aldehyde functional group. Catalytic hydrogenation Catalytic hydrogenation can be used to reduce amides to amines; however, the process often req ...

References

{{Oxides Rhenium compounds Acidic oxides Hydrogenation catalysts