Iodine heptafluoride, also known as iodine(VII) fluoride or iodine fluoride, is an interhalogen compound with the chemical formula I F₇. It has an unusual pentagonal bipyramidal structure, as predicted by

VSEPR theory Valence shell electron pair repulsion (VSEPR) theory ( , ), is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm the ...

. The molecule can undergo a

pseudorotation In chemistry, a pseudorotation is a set of intramolecular movements of attached groups (i.e., ligands) on a highly symmetric molecule, leading to a molecule indistinguishable from the initial one. The International Union of Pure and Applied Chem ...

al rearrangement called the

Bartell mechanism The Bartell mechanism is a pseudorotational mechanism similar to the Berry mechanism. It occurs only in molecules with a pentagonal bipyramidal molecular geometry, such as IF7. This mechanism was first predicted by H. B. Bartell. The mechanism exc ...

, which is like the

Berry mechanism The Berry mechanism, or Berry pseudorotation mechanism, is a type of vibration causing molecules of certain geometries to isomerize by exchanging the two axial ligands (see Figure at right) for two of the equatorial ones. It is the most widely ac ...

but for a heptacoordinated system. It forms colourless crystals, which melt at 4.5 °C: the liquid range is extremely narrow, with the boiling point at 4.77 °C. The dense vapor has a mouldy, acrid odour. The molecule has D_5h symmetry.

Preparation

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 Potassium iodide is a chemical compound, medication, and dietary supplement. It is a medication used for treating hyperthyroidism, in radiation emergencies, and for protecting the thyroid gland when certain types of radiopharmaceuticals are u ...

to minimize the formation of IOF₅, an impurity arising by hydrolysis. Iodine heptafluoride is also produced as a by-product when

dioxygenyl hexafluoroplatinate Dioxygenyl hexafluoroplatinate is a compound with formula O2PtF6. It is a hexafluoroplatinate of the unusual dioxygenyl cation, O2+, and is the first known compound containing this cation. It can be produced by the reaction of dioxygen with platin ...

is used to prepare other platinum(V) compounds such as potassium hexafluoroplatinate(V), using

potassium fluoride Potassium fluoride is the chemical compound with the formula KF. After hydrogen fluoride, KF is the primary source of the fluoride ion for applications in manufacturing and in chemistry. It is an alkali halide and occurs naturally as the rare ...

in iodine pentafluoride solution: :2 O₂PtF₆ + 2 KF + IF₅ → 2 KPtF₆ + 2 O₂ + IF₇

Reactions

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

Safety considerations

IF₇ is highly irritating to both the skin and the

mucous membranes A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

. It also is a strong oxidizer and can cause fire on contact with organic material.

References

External links

WebBook page for IF7
* ttp://www.webelements.com/webelements/compounds/text/I/F7I1-16921963.html web elements listing {{fluorine compounds Fluorides Iodine compounds Interhalogen compounds Oxidizing agents Hypervalent molecules