Iodine monofluoride
IUPAC name
Iodine monofluoride
Other names
Iodine fluoride
3D model (JSmol)
  • InChI=1S/FI/c1-2 checkY
  • InChI=1/FI/c1-2
  • FI
Molar mass 145.903 g/mol
Appearance unstable brown solid
Melting point −45 °C (−49 °F; 228 K)
Related compounds
Other anions
Iodine monochloride
Iodine monobromide
Astatine monoiodide
Other cations
Chlorine monofluoride
Bromine monofluoride
Related compounds
Iodine trifluoride
Iodine pentafluoride
Iodine heptafluoride
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 monofluoride is an interhalogen compound of iodine and fluorine with formula IF. It is a chocolate-brown solid that decomposes at 0 °C,[1] disproportionating to elemental iodine and iodine pentafluoride:

5 IF → 2 I2 + IF5

However, its molecular properties can still be precisely determined by spectroscopy: the iodine-fluorine distance is 190.9 pm and the I−F bond dissociation energy is around 277 kJ mol−1. At 298 K, its standard enthalpy change of formation is ΔfH° = −95.4 kJ mol−1, and its Gibbs free energy is ΔfG° = −117.6 kJ mol−1.

It can be generated, albeit only fleetingly, by the reaction of the elements at −45 °C in CCl3F:

I2 + F2 → 2 IF

It can also be generated by the reaction of iodine with iodine trifluoride at −78 °C in CCl3F:

I2 + IF3 → 3 IF

The reaction of iodine with silver(I) fluoride at 0 °C also yields iodine monofluoride:

I2 + AgF → IF + AgI


Iodine monofluoride is used to produce pure nitrogen triiodide:[2]

BN + 3 IF → NI3 + BF3

See also


  1. ^ Eagleson, Mary (1994). Concise Encyclopedia of Chemistry. Walter de Gruyter. ISBN 978-3-11-011451-5.
  2. ^ Inis Tornieporth-Oetting; Thomas Klapötke (1990). "Nitrogen Triiodide". Angewandte Chemie International Edition. VCH Verlagsgesellschaft mbH. 29 (6): 677–679. doi:10.1002/anie.199006771.