Heptafluoride Explained

Heptafluoride typically refers to compounds with the formula R_nM_xF₇^y− or R_nM_xF₇^y+, where n, x, and y are independent variables and R any substituent.

Binary heptafluorides

The only binary heptafluorides are iodine heptafluoride (IF₇), rhenium heptafluoride (ReF₇), and gold heptafluoride (AuF₇). Only IF₇ and ReF₇ are true heptafluorides, however, as AuF₇ is actually a coordination complex of gold pentafluoride (AuF₅) and molecular fluorine; therefore, the correct chemical formula of gold heptafluoride is actually AuF₅·F₂.^[1]

Heptafluoride anions

A commercially important heptafluoride anion is the heptafluorotantalate anion, TaF₇²⁻. It is an intermediate in the purification of tantalum. Many dimeric and oligomeric heptafluorides have been observed or proposed. One example is B₂F₇⁻.^[2]

In the area of organofluorine chemistry, many heptafluorides are known. A prominent example is heptafluorobutyric acid. This species and its conjugate base heptafluorobutyrate (C₃F₇CO₂⁻) are precursors to surfactants.

Complex heptafluorides

Many compounds that are not discrete ions or molecules also are heptafluorides.^[3]

References

1. After 20 Years, Theoretical Evidence That "AuF₇" Is Actually AuF₅·F₂. Inorganic Chemistry. 2007-05-31. 46. 13. 5338–5342. 10.1021/ic700431s. Himmel. Daniel. Riedel. Sebastian. 17511450.
2. J. S. Hartman, P. Stilbs "Direct observation of the heptafluorodiborate(III) ion, B₂F₇⁻" J. Chem. Soc., Chem. Commun., 1975, pages 566-567.
3. Grosse, L.; Hoppe, R. "Zur Kenntnis von Sr₂RhF₇" Zeitschrift für Anorganische und Allgemeine Chemie (1987), 552, 123-31.