Rhenium(VII) oxide

Rhenium(VII) 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.^[2]

Rhenium(VII) oxide

Names
Other names Rhenium heptoxide
Identifiers
CAS Number	1314-68-7 Y
3D model (JSmol)	Interactive image
ECHA InfoCard	100.013.857
EC Number	215-241-9
PubChem CID	123106
UNII	0DJ421156F Y
CompTox Dashboard (EPA)	DTXSID00894901
InChI Key: NBGOSNNAAHDRLK-UHFFFAOYSA-N InChI=1S/7O.2Re
SMILES O=[Re](=O)(=O)O[Re](=O)(=O)=O
Properties
Chemical formula	Re2O7
Molar mass	484.40298 g/mol
Appearance	yellow crystalline powder
Density	6.103 g/cm3, solid
Melting point	360 °C (680 °F; 633 K)
Boiling point	sublime
Solubility in water	Hydrolyses
Hazards
GHS labelling:[1]
Pictograms
Signal word	Danger
Hazard statements	H314
Precautionary statements	P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501
Related compounds
Related compounds	Manganese(VII) oxide; technetium(VII) oxide; perrhenic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

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.^[3]

Synthesis and reactions

Rhenium(VII) oxide is formed when metallic rhenium or its oxides or sulfides are oxidized at 500–700 °C (900–1,300 °F) in air.^[4]

Re₂O₇ dissolves in water to give perrhenic acid.

Heating Re₂O₇ gives rhenium dioxide, a reaction signalled by the appearance of the dark blue coloration:^[5]

2Re₂O₇ → 4ReO₂ + 3O₂

Using tetramethyltin, it converts to methylrhenium trioxide ("MTO"), a catalyst for oxidations:^[6]

Re₂O₇ + 2Sn(CH₃)₄ → CH₃ReO₃ + (CH₃)₃SnOReO₃

In a related reaction, it reacts with hexamethyldisiloxane to give the siloxide:^[4]

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

Uses

Hydrogenation catalyst

Rhenium(VII) oxide finds some use in organic synthesis as a catalyst for ethenolysis,^[7] carbonyl reduction and amide reduction.^[8]

References

1. "Rhenium(VII) oxide". pubchem.ncbi.nlm.nih.gov. Retrieved 14 December 2021.
2. Georg Nadler, Hans (2000). "Rhenium and Rhenium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a23_199. ISBN 3527306730.
3. Wells, A.F. (1984). Structural Inorganic Chemistry. Oxford: Clarendon Press. ISBN 0-19-855370-6.
4. Schmidt, Max; Schmidbaur, Hubert (1967). Trimethylsilyl Perrhenate. Inorganic Syntheses. Vol. 9. pp. 149–151. doi:10.1002/9780470132401.ch40. ISBN 9780470132401.
5. Glemser, O. (1963). "Rhenium". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry. Vol. 1 (2nd ed.). Academic Press. pp. 1476–1485.
6. W. A. Herrmann; F. E. Kuhn (1997). "Organorhenium Oxides". Acc. Chem. Res. 30 (4): 169–180. doi:10.1021/ar9601398.
7. Lionel Delaude; Alfred F. Noels, "Metathesis", Kirk-Othmer Encyclopedia of Chemical Technology, New York: John Wiley, doi:10.1002/0471238961.metanoel.a01, ISBN 9780471238966
8. Nishimura, Shigeo (2001). Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis (1st ed.). New York: Wiley-Interscience. pp. 42–43, 182, 389–390, & 408. ISBN 978-0-471-39698-7.