Iodine heptafluoride is an interhalogen compound with the chemical formula IF7.
It has an unusual pentagonal bipyramidal structure, with D5h symmetry, as predicted by VSEPR theory. The molecule can undergo a pseudorotational rearrangement called the Bartell mechanism, which is like the Berry mechanism but for a heptacoordinated system.
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Names | |||
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Other names Iodine(VII) fluoride Heptafluoroiodine | |||
Identifiers | |||
3D model (JSmol) | |||
ChemSpider | |||
ECHA InfoCard | 100.037.241 | ||
PubChem CID | |||
UNII | |||
CompTox Dashboard (EPA) | |||
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Properties | |||
IF7 | |||
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 | |||
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). |
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.
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. 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:
Iodine heptafluoride decomposes at 200 °C to fluorine gas and iodine pentafluoride.
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.
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