Perrhenate

The perrhenate ion is the anion with the formula ReO−4, or a compound containing this ion. The perrhenate anion is tetrahedral, being similar in size and shape to perchlorate and the valence isoelectronic permanganate. The perrhenate anion is stable over a broad pH range and can be precipitated from solutions with the use of organic cations. At normal pH, perrhenate exists as metaperrhenate (ReO−4), but at high pH mesoperrhenate (ReO3−5) forms. Perrhenate, like its conjugate acid perrhenic acid, features rhenium in the oxidation state of +7 with a d0 configuration. Solid perrhenate salts takes on the color of the cation.[1]

## Contents

* 1 Preparation
* 2 Reactions of perrhenates
* 2.1 Basicity
* 2.2 Condensation
* 2.3 Reaction with sulfide
* 2.4 Redox
* 2.5 Complement to pertechnetate
* 3 References
* 4 See also

## Preparation

Typical perrhenate salts are the alkali metal derivatives and ammonium perrhenate. These salts are prepared by oxidation of rhenium compounds with nitric acid followed by neutralization of the resulting perrhenic acid.[2][3][4] Addition of tetrabutylammonium chloride to aqueous solutions of sodium perrhenate gives tetrabutylammonium perrhenate, which is soluble in organic solvents.[5]

## Reactions of perrhenates

### Basicity

Perrhenate anion is a weaker base than Cl− or Br− but stronger than ClO−4 or BF−4. Silver perrhenate reacts with trimethylsilyl chloride to give the silyl "ester" (CH3)3SiOReO3.[6]

### Condensation

Perrhenate may undergo condensation with formation of small rhenium polyoxometalate Re4O2−15 [7] where one central Re has octahedral oxygen coordination while 3 other are tetrahedral.

### Reaction with sulfide

With sulfide sources such as hydrogen sulfide, ReO−4 converts to tetrathioperrhenate anion ReS−4. An intermediate is [ReO3S]−.[8]

### Redox

Unlike the related permanganate, perrhenate is nonoxidising. Replacement of some oxo ligands induces redox however. Thus the perrhenate ion reacts with the cyanide to give trans-[ReO2(CN)4]3−. Treatment of tetrabutylammonium perrhenate with trimethylsilyl chloride produces the oxychloride of Re(V):[5]

Bu4N[ReO4] + 6 Me3SiCl → Bu4N[ReOCl4] + 3 (Me3Si)2O + Cl2

### Complement to pertechnetate

The chemistry of the perrhenate ion is similar to that of the pertechnetate ion TcO−4. For this reason, perrhenate is sometimes used as a carrier for trace levels of pertechnetate, for instance in nuclear medicine scanning procedures. Perrhenate is also used as a safer alternative to pertechnetate for nuclear waste vitrification studies, such as volatility[9] or encapsulation in solids.[10]

## References

1. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
2. ↑ O. Glemser "Rhenium" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1476-85.
3. ↑ Richard J. Thompson (1966). "Ammonium Perrhenate". Inorganic Syntheses. 8. pp. 171–173. doi:10.1002/9780470132395.ch44. ISBN 9780470132395.
4. ↑ Wm. T. Smith, S. Harmon Long (1948). "The Salts of Perrhenic Acid. I. The Alkali Metals and Ammonium". Journal of the American Chemical Society 70 (1): 354–356. doi:10.1021/ja01181a110.
5. ↑ 5.0 5.1 Dilworth, J. R.; Hussain, W.; Hutson, A. J.; Jones, C. J.; McQuillan, F. S. (1997). "Tetrahalo Oxorhenate Anions". Inorganic Syntheses. pp. 257–262. doi:10.1002/9780470132623.ch42. ISBN 9780470132623.
6. ↑ Kühn, Fritz E.; Santos, Ana M.; Herrmann, Wolfgang A. (2005). "Organorhenium(VII) and Organomolybdenum(VI) Oxides: Syntheses and Application in Olefin Epoxidation". Dalton Transactions (15): 2483–91. doi:10.1039/b504523a. PMID 16025165.
7. ↑ Volkov, Mikhail A.; Novikov, Anton P.; Borisova, Nataliya E.; Grigoriev, Mikhail S.; German, Konstantin E. (2023-08-21). "Intramolecular Re···O Nonvalent Interactions as a Stabilizer of the Polyoxorhenate(VII)" (in en). Inorganic Chemistry 62 (33): 13485–13494. doi:10.1021/acs.inorgchem.3c01863. ISSN 0020-1669. https://pubs.acs.org/doi/10.1021/acs.inorgchem.3c01863.
8. ↑ Goodman, J. T.; Rauchfuss, T. B. (2002). "Useful Reagents and Ligands". Inorganic Syntheses. 33. pp. 107–110. doi:10.1002/0471224502.ch2. ISBN 9780471208259.
9. ↑ Kim, Dongsang; Kruger, Albert (2018). "Volatile species of technetium and rhenium during waste vitrification". Journal of Non-Crystalline Solids 481: 41–50. doi:10.1016/j.jnoncrysol.2017.10.013. Bibcode: 2018JNCS..481...41K.
10. ↑ Luksic, Steven; Riley, Brian; Parker, Kent; Hrma, Pavel (2016). "Sodalite as a vehicle to increase Re retention in waste glass simulant during vitrification". Journal of Nuclear Materials 479: 331–337. doi:10.1016/j.jnucmat.2016.07.002. Bibcode: 2016JNuM..479..331L.

## See also

* Permanganate
* Pertechnetate

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