Heptafluoride typically refers to compounds with the formula R<sub>n</sub>M<sub>x</sub>F<sub>7</sub><sup>yâÂÂ</sup> or R<sub>n</sub>M<sub>x</sub>F<sub>7</sub><sup>y+</sup>, where n, x, and y are independent variables and R any substituent.
The only binary heptafluorides are iodine heptafluoride (IF<sub>7</sub>), rhenium heptafluoride (ReF<sub>7</sub>), and gold heptafluoride (AuF<sub>7</sub>). Only IF<sub>7</sub> and ReF<sub>7</sub> are true heptafluorides, however, as AuF<sub>7</sub> is actually a coordination complex of gold pentafluoride (AuF<sub>5</sub>) and molecular fluorine; therefore, the correct chemical formula of gold heptafluoride is actually AuF<sub>5</sub>÷F<sub>2</sub>.
A commercially important heptafluoride anion is the heptafluorotantalate anion, TaF<sub>7</sub><sup>2âÂÂ</sup>. It is an intermediate in the purification of tantalum. Many dimeric and oligomeric heptafluorides have been observed or proposed. One example is B<sub>2</sub>F<sub>7</sub><sup>âÂÂ</sup>.
In the area of organofluorine chemistry, many heptafluorides are known. A prominent example is heptafluorobutyric acid. This species and its conjugate base heptafluorobutyrate (C<sub>3</sub>F<sub>7</sub>CO<sub>2</sub><sup>âÂÂ</sup>) are precursors to surfactants.
Many compounds that are not discrete ions or molecules also are heptafluorides.