title: Heptafluoride
text: # Heptafluoride
  
  Heptafluoride typically refers to compounds with the formula $R_nM_xF_7^{y−}$ or $R_nM_xF_7^{y+},$ where n, x, and y are independent variables and R any substituent.
  
  ## Binary heptafluorides
  
  The only binary heptafluorides are iodine heptafluoride $(IF_7),$ rhenium heptafluoride $(ReF_7),$ and gold heptafluoride $(AuF_7).$ Only $IF_7$ and $ReF_7$ are true heptafluorides, however, as $AuF_7$ is actually a coordination complex of gold pentafluoride $(AuF_5)$ and molecular fluorine; therefore, the correct chemical formula of gold heptafluoride is actually $AuF_5·F_2.$
  
  ## Heptafluoride anions
  
  A commercially important heptafluoride anion is the heptafluorotantalate anion, $TaF_7^{2−}.$ It is an intermediate in the purification of tantalum. Many dimeric and oligomeric heptafluorides have been observed or proposed. One example is $B_2F_7^−.$
  
  In the area of organofluorine chemistry, many heptafluorides are known. A prominent example is heptafluorobutyric acid. This species and its conjugate base heptafluorobutyrate $(C_3F_7CO_2^−)$ are precursors to surfactants.
  
  ## Complex heptafluorides
  
  Many compounds that are not discrete ions or molecules also are heptafluorides.
  
  