Iodine heptafluoride
Structure of iodine heptafluoride(IF7)
Iodine heptafluoride
Iodine heptafluoride
Iodine heptafluoride
Iodine heptafluoride
Other names
Iodine(VII) fluoride
3D model (JSmol)
ECHA InfoCard 100.037.241 Edit this at Wikidata
  • InChI=1S/F7I/c1-8(2,3,4,5,6)7 checkY
  • InChI=1/F7I/c1-8(2,3,4,5,6)7
  • FI(F)(F)(F)(F)(F)F
Molar mass 259.90 g/mol
Appearance colorless gas
Density 2.6 g/cm3 (6 °C)
2.7 g/cm3 (25 °C)
Melting point 4.5 °C (40.1 °F; 277.6 K) (triple point)
Boiling point 4.8 °C (40.6 °F; 277.9 K) (sublimes at 1 atm)
soluble [1]
Related compounds
Related compounds
iodine pentafluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Iodine heptafluoride is an interhalogen compound with the chemical formula IF7.[2][3] It has an unusual pentagonal bipyramidal structure, with D5h symmetry, as predicted by VSEPR theory.[4] The molecule can undergo a pseudorotational rearrangement called the Bartell mechanism, which is like the Berry mechanism but for a heptacoordinated system.[5]

Below 4.5 °C, IF7 forms a snow-white powder of colorless crystals, melting at 5-6 °C. However, this melting is difficult to observe, as the liquid form is thermodynamically unstable at 760 mmHg: instead, the compound begins to sublime at 4.77 °C. The dense vapor has a mouldy, acrid odour.[6][7]


IF7 is prepared by passing F2 through liquid IF5 at 90 °C, then heating the vapours to 270 °C. Alternatively, this compound can be prepared from fluorine and dried palladium or potassium iodide to minimize the formation of IOF5, an impurity arising by hydrolysis.[8][9] Iodine heptafluoride is also produced as a by-product when dioxygenyl hexafluoroplatinate is used to prepare other platinum(V) compounds such as potassium hexafluoroplatinate(V), using potassium fluoride in iodine pentafluoride solution:[10]

2 O2PtF6 + 2 KF + IF5 → 2 KPtF6 + 2 O2 + IF7


Iodine heptafluoride decomposes at 200 °C to fluorine gas and iodine pentafluoride.[11]

Safety considerations

IF7 is highly irritating to both the skin and the mucous membranes. It also is a strong oxidizer and can cause fire on contact with organic material.


  1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  2. ^ Macintyre, J. E. (Ed.). (1992). Dictionary of Inorganic Compounds (Vol. 3). London: Chapman & Hall.
  3. ^ O'Neil, Maryadele J. (Ed.). (2001). The Merck Index (13th ed.). Whitehouse Station, NJ: Merck.
  4. ^ K. O. Christe; E. C. Curtis; D. A. Dixon (1993). "On the problem of heptacoordination: vibrational spectra, structure, and fluxionality of iodine heptafluoride". Journal of the American Chemical Society. 115 (4): 1520–1526. doi:10.1021/ja00057a044.
  5. ^ W. J. Adams; H. Bradford Thompson; L. S. Bartell (1970). "Structure, Pseudorotation, and Vibrational Mode Coupling in IF7: An Electron Diffraction Study" (PDF). Journal of Chemical Physics. 53 (10): 4040–4046. Bibcode:1970JChPh..53.4040A. doi:10.1063/1.1673876. hdl:2027.42/71219.
  6. ^ Lide, David R. (2011). The CRC Handbook of Chemistry and Physics, 89th ed. p. 4-67.
  7. ^ Ruff & Keim 1930, pp. 180–182: "Das reine Jod-7-fluorid ist bei Zimmer­temperatur ein farbloses Gas, das an der Luft infolge seiner Umsetzung mit dem Wasser­dampf Nebel bildet und muffig sauer riecht. Beim Abkühlen wird es je nach den Versuchs­bedingungen als leicht bewegliche, farblose Flüssigkeit als schneeweißes lockeres Pulver oder in Form farbloser Kristalle erhalten....Die Schmelz­temperatur wurde durch Eintauchen von Proben, die in Quarzröhrchen eingeschmolzen waren, in Bäder passender Temperatur ermittelt und zu 5 bis 6° C gefunden. [Durch] Messung der Dampfdrucke...gelangt man zu der Gleichung
    ....Für den Druck von 760 mm errechnet sich eine Temperatur von 4,5° C. [Pure iodine heptafluoride is at room temperature a colorless gas, which forms a fog in air on account of its reaction with the humidity and smells musty and acrid. When cooled, it takes the form, depending on experimental conditions, of a free-flowing colorless liquid, a loose snow-white powder, or colorless crystals....The melting point was measured by immersion of a probe in a bath of the right temperature, which was melting in a little quartz tube and found to be 5‑6 °C. [From] measurement of the vapor arrives at the equation
    ....At a pressure of 760 mm it computes a temperature of 4.5 °C.]"
  8. ^ Schumb, W. C.; Lynch, M. A. (1950). "Iodine Heptafluoride". Industrial & Engineering Chemistry. 42 (7): 1383–1386. doi:10.1021/ie50487a035.
  9. ^ Ruff & Keim 1930.
  10. ^ Beveridge, A. D.; Clark, H. C. (1967). "Pentahalides of the Transition Metals". In Gutmann, Viktor (ed.). Halogen Chemistry. Vol. 3. Academic Press. pp. 179–226. ISBN 9780323148474.
  11. ^ Кнунянц, И. Л. (1990). Химическая энциклопедия : в пяти томах (in Russian). Советская Энциклопедия. p. 496. ISBN 5-85270-008-8. OCLC 19556260.

Common sources