Rhenium(VII) oxide
{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 417132838
| Name = Rhenium(VII) oxide
| ImageFile = Kristallstruktur Rhenium(VII)-oxid.png
| ImageSize =
| ImageName = Rhenium(VII) oxide
| ImageFile1 = Rhenium heptoxide.png
| OtherNames = Rhenium heptoxide
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 1314-68-7
| EINECS = 215-241-9
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 0DJ421156F
| PubChem = 123106
| InChI = 1S/7O.2Re
| StdInChIKey = NBGOSNNAAHDRLK-UHFFFAOYSA-N
| SMILES = O=[Re](=O)(=O)O[Re](=O)(=O)=O
}}
|Section2={{Chembox Properties
| Formula = Re2O7
| MolarMass = 484.40298 g/mol
| Appearance = yellow crystalline powder
| Density = 6.103 g/cm3, solid
| MeltingPtC = 360
| BoilingPt = sublime
| Solubility = Hydrolyses
}}
|Section7={{Chembox Hazards
| GHSPictograms = {{GHS05}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|314}}
| PPhrases = {{P-phrases|260|264|280|301+330+331|303+361+353|304+340|305+351+338|310|321|363|405|501}}
}}
|Section8={{Chembox Related
| OtherCompounds = Manganese(VII) oxide; technetium(VII) oxide; perrhenic acid
}}
}}
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.{{Ullmann|doi=10.1002/14356007.a23_199|title=Rhenium and Rhenium Compounds|year=2000|last1=Georg Nadler|first1=Hans|isbn=3527306730}}
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.{{cite book |last=Wells |first=A.F. |year=1984 |title=Structural Inorganic Chemistry |place=Oxford |publisher=Clarendon Press |isbn=0-19-855370-6}}
Synthesis and reactions
Rhenium(VII) oxide is formed when metallic rhenium or its oxides or sulfides are oxidized at {{cvt|500|-|700|°C|-2}} in air.{{cite book |title=Trimethylsilyl Perrhenate |series=Inorganic Syntheses |year=1967 |volume=9 |last1=Schmidt |first1=Max |last2=Schmidbaur |first2=Hubert |pages=149–151 |isbn=9780470132401 |doi=10.1002/9780470132401.ch40}}
Re2O7 dissolves in water to give perrhenic acid.
Heating Re2O7 gives rhenium dioxide, a reaction signalled by the appearance of the dark blue coloration:{{Cite book |first=O.|last=Glemser |title=Handbook of Preparative Inorganic Chemistry |publisher=Academic Press |year=1963 |editor-last=G. Brauer |edition=2nd |volume=1 |pages=1476–1485 |chapter=Rhenium |chapter-url=https://archive.org/details/Handbook_of_Preparative_Inorganic_Chemistry_1_2_Brauer/page/n1522}}
:2Re2O7 → 4ReO2 + 3O2
Using tetramethyltin, it converts to methylrhenium trioxide ("MTO"), a catalyst for oxidations:{{cite journal |author1=W. A. Herrmann |author2=F. E. Kuhn |title=Organorhenium Oxides |year=1997 |journal=Acc. Chem. Res. |volume=30 |issue=4 |pages=169–180 |doi=10.1021/ar9601398}}
:Re2O7 + 2Sn(CH3)4 → CH3ReO3 + (CH3)3SnOReO3
In a related reaction, it reacts with hexamethyldisiloxane to give the siloxide:
: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,{{Kirk-Othmer |title=Metathesis|author1=Lionel Delaude |author2=Alfred F. Noels |doi=10.1002/0471238961.metanoel.a01}} carbonyl reduction and amide reduction.{{cite book |last1=Nishimura |first1=Shigeo |title=Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis |date=2001 |publisher=Wiley-Interscience |location=New York |isbn=978-0-471-39698-7 |pages=42-43, 182, 389-390, & 408 |edition=1st |url=https://books.google.com/books?id=RjZRAAAAMAAJ&q=0471396982}}
References
{{reflist}}
{{Rhenium compounds}}
{{Oxides}}