Gold pentafluoride

Gold(V) fluoride

Names
IUPAC name Gold(V) fluoride
Other names Gold pentafluoride Perauric fluoride
Identifiers
CAS Number	57542-85-5
Properties
Chemical formula	AuF5
Molar mass	291.959 g/mol
Appearance	red unstable solid
Melting point	60 °C (140 °F; 333 K) (decomposes)
Solubility in water	Decomposes
Structure
Crystal structure	orthorhombic (Pnma)
Hazards
Main hazards	Corrosive, toxic
Related compounds
Other cations	SbF5, BrF5, IF5
Related compounds	AuF3, AuF7
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Gold(V) fluoride is the inorganic compound with the formula Au₂F₁₀. This fluoride compound features gold in its highest known oxidation state. This red solid dissolves in hydrogen fluoride but these solutions decompose, liberating fluorine.

The structure of gold(V) fluoride in the solid state is centrosymmetric with hexacoordinated gold and an octahedral arrangement of the fluoride centers on each gold center. It is the only known dimeric pentafluoride; other pentafluorides are monomeric (P, As, Cl, Br, I), tetrameric (Nb, Ta, Cr, Mo, W, Tc, Re, Ru, Os, Rh, Ir, Pt), or polymeric (Bi, V, U).^[1] In the gas phase, a mixture of dimer and trimer in the ratio 82:18 has been observed.

Gold pentafluoride is the strongest known fluoride ion acceptor, exceeding the acceptor tendency of even antimony pentafluoride.

Synthesis

Gold(V) fluoride can be synthesized by heating gold metal in an atmosphere of oxygen and fluorine to 370 °C at 8 atmospheres to form dioxygenyl hexafluoroaurate:^[2][3]

Au(s) + O₂(g) + 3 F₂(g) → O₂AuF₆(s)

This salt decomposes at 180 °C to produce the pentafluoride:

2 O₂AuF₆(s) → Au₂F₁₀ (s) + 2 O₂(g) + F₂(g)

Krypton difluoride is primarily a powerful oxidising and fluorinating agent. It can oxidise gold to its highest-known oxidation state, +5:^[4]

7 KrF
2 (g) + 2 Au (s) → 2 KrF+
AuF−
6 (s) + 5 Kr (g)

KrF+
AuF−
6 decomposes at 60 °C into gold(V) fluoride and gaseous krypton and fluorine:^[5]

2 KrF+
AuF−
6 → Au
2F
10 (s) + 2 Kr (g) + 2 F
2 (g)

References

1. In-Chul Hwang, Konrad Seppelt "Gold Pentafluoride: Structure and Fluoride Ion Affinity" Angewandte Chemie International Edition 2001, volume 40, 3690-3693. doi: 10.1002/1521-3773(20011001)40:19<3690::AID-ANIE3690>3.0.CO;2-5
2. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.
3. Emeléus, H. J.; Sharpe, A. G. (1983). Advances in Inorganic Chemistry and Radiochemistry. Academic Press. p. 83. ISBN 0-12-023627-3.
4. W. Henderson (2000). Main group chemistry. Great Britain: Royal Society of Chemistry. p. 149. ISBN 0-85404-617-8.
5. Charlie Harding; David Arthur Johnson; Rob Janes (2002). Elements of the p block. Great Britain: Royal Society of Chemistry. p. 94. ISBN 0-85404-690-9.