Iodine heptafluoride is an interhalogen compound with the chemical formula I F₇. It has an unusual pentagonal bipyramidal structure, with D_5h symmetry, as predicted by

VSEPR theory Valence shell electron pair repulsion (VSEPR) theory ( , ) is a conceptual model, 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 Gill ...

. The molecule can undergo a pseudorotational rearrangement called the Bartell mechanism, which is like the

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

but for a heptacoordinated system. 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.

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 Palladium is a chemical element; it has symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1802 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas (formally 2 Pallas), ...

or potassium iodide to minimize the formation of IOF₅, an impurity arising by hydrolysis. 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 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 salt and occurs naturally as the ...

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 membrane 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 ...

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

References

Common sources

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