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Perrhenic acid

Perrhenic acid
Perrhenic acid
Ball-and-stick model of the perrhenic acid molecule
Names
IUPAC name
Tetraoxorhenic(VII) acid
Other names
Hydrated rhenium(VII) oxide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.968 Edit this at Wikidata
EC Number
  • 237-380-4
RTECS number
  • TT4550000
  • InChI=1S/2H2O.7O.2Re/h2*1H2;;;;;;;;; checkY
    Key: JOTGKJVGIIKFIQ-UHFFFAOYSA-N checkY
  • InChI=1/2H2O.7O.2Re/h2*1H2;;;;;;;;;/rH4O9Re2/c1-10(2,3)9-11(4,5,6,7)8/h4-5H2
    Key: JOTGKJVGIIKFIQ-SEUCOXMMAB
  • [OH2+][Re-2](=O)(=O)(=O)([OH2+])O[Re](=O)(=O)=O
Properties
H4Re2O9 (solid)
HReO4 (gas)
Molar mass 251.2055 g/mol
Appearance Pale yellow solid
Boiling point sublimes
Soluble
Acidity (pKa) -1.25[1]
Conjugate base Perrhenate
Structure
octahedral-tetrahedral (solid)
tetrahedral (gas)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Corrosive
GHS labelling:
GHS05: CorrosiveGHS07: Exclamation mark
Danger
H302, H314, H332
P260, P261, P264, P270, P271, P280, P301+P312, P301+P330+P331, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P312, P321, P330, P363, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability (red): no hazard codeInstability (yellow): no hazard codeSpecial hazards (white): no code
3
Flash point Non-flammable
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Perrhenic acid is the chemical compound with the formula Re2O7(H2O)2. It is obtained by evaporating aqueous solutions of Re2O7. Conventionally, perrhenic acid is considered to have the formula HReO4, and a species of this formula forms when rhenium(VII) oxide sublimes in the presence of water or steam.[2] When a solution of Re2O7 is kept for a period of months, it breaks down and crystals of HReO4·H2O are formed, which contain tetrahedral ReO−4.[3] For most purposes, perrhenic acid and rhenium(VII) oxide are used interchangeably. Rhenium can be dissolved in nitric or concentrated sulfuric acid to produce perrhenic acid.

Properties

The structure of solid perrhenic acid is [O3Re−O−ReO3(H2O)2].[4] This species is a rare example of a metal oxide coordinated to water; most often metal–oxo–aquo species are unstable with respect to their corresponding hydroxides:

M(O)(H2O) → M(OH)2

The two rhenium atoms have different bonding geometries, with one being tetrahedral and the other octahedral, and with the water ligands coordinated to the latter.

Gaseous perrhenic acid is tetrahedral, as suggested by its formula HReO4.

Reactions

Perrhenic acid or the related anhydrous oxide Re2O7 converts to dirhenium heptasulfide upon treatment with hydrogen sulfide:

Re2O7 + 7 H2S → Re2S7 + 7 H2O

The heptasulfide catalyzes various reductions.[5]

Perrhenic acid in the presence of hydrochloric acid undergoes reduction in the presence of thioethers and tertiary phosphines to give rhenium(V) complexes with the formula ReOCl3L2.[6]

Perrhenic acid combined with platinum on a support gives rise to a useful hydrogenation and hydrocracking catalyst for the petroleum industry.[7] For example, silica impregnated with a solution of perrhenic acid is reduced with hydrogen at 500 °C.[citation needed] This catalyst is used in the dehydrogenation of alcohols and also promotes the decomposition of ammonia.

Catalysis

Perrhenic acid is a precursor to a variety of homogeneous catalysts, some of which are promising in niche applications that can justify the high cost of rhenium. In combination with tertiary arsines, perrhenic acid gives a catalyst for the epoxidation of alkenes with hydrogen peroxide.[8] Perrhenic acid catalyses the dehydration of oximes to nitriles.[9]

Other uses

Perrhenic acid is also used in the manufacture of x-ray targets.[10][11]

See also

References

  1. ^ http://www.iupac.org/publications/pac/1998/pdf/7002x0355.pdf [bare URL PDF]
  2. ^ Glemser, O.; Müller, A.; Schwarzkopf, H. (1964). "Gasförmige Hydroxide. IX. Über ein Gasförmiges Hydroxid des Rheniums". Zeitschrift für anorganische und allgemeine Chemie (in German). 334 (1–2): 21–26. doi:10.1002/zaac.19643340105..
  3. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. ^ Beyer, H.; Glemser, O.; Krebs, B. "Dirhenium Dihydratoheptoxide Re
    2    O
    7    (OH
    2    )
    2     – New Type of Water Bonding in an Aquoxide" Angewandte Chemie, International Edition English 1968, Volume 7, Pages 295 - 296. doi:10.1002/anie.196802951.
  5. ^ Schwarz, D. E.; Frenkel, A. I.; Nuzzo, R. G.; Rauchfuss, T. B.; Vairavamurthy, A. (2004). "Electrosynthesis of ReS
    4    . XAS Analysis of ReS
    2    , Re
    2    S
    7    , and ReS
    4    ". Chemistry of Materials. 16: 151–158. doi:10.1021/cm034467v.
  6. ^ Parshall, G. W.; Shive, L. W.; Cotton, F. A. (1997). Phosphine Complexes of Rhenium. Inorganic Syntheses. Vol. 17. pp. 110–112. doi:10.1002/9780470132487.ch31. ISBN 9780470132487.
  7. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  8. ^ van Vliet, M. C. A.; Arends, I. W. C. E.; Sheldon, R. A. (1999). "Rhenium Catalysed Epoxidations with Hydrogen Peroxide: Tertiary Arsines as Effective Cocatalysts". J. Chem. Soc., Perkin Trans. 1 (3): 377–80. doi:10.1039/a907975k.
  9. ^ Ishihara, K.; Furuya, Y.; Yamamoto, H. (2002). "Rhenium(VII) Oxo Complexes as Extremely Active Catalysts in the Dehydration of Primary Amides and Aldoximes to Nitriles". Angewandte Chemie International Edition. 41 (16): 2983–2986. doi:10.1002/1521-3773(20020816)41:16<2983::AID-ANIE2983>3.0.CO;2-X. PMID 12203432.
  10. ^ http://www.gehealthcare.com/usen/service/time_material_support/docs/Radplus2100.pdf[permanent dead link]
  11. ^ X-ray#Sources
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