Iodine monofluoride

Iodine monofluoride is an interhalogen compound of iodine and fluorine with formula IF. It is a chocolate-brown solid that decomposes at 0 °C, 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 Δ_fH° = −95.4 kJ mol⁻¹, and its Gibbs free energy is Δ_fG° = −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