Iodine heptafluoride
Iodine heptafluoride is an interhalogen compound with the chemical formula IF7.[1][2] It has an unusual pentagonal bipyramidal structure, with D5h symmetry, as predicted by VSEPR theory.[3] The molecule can undergo a pseudorotational rearrangement called the Bartell mechanism, which is like the Berry mechanism but for a heptacoordinated system.[4]
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.[5][6]
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 to minimize the formation of IOF5, an impurity arising by hydrolysis.[7]Template:Sfn 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:[8]
- 2 O2PtF6 + 2 KF + IF5 → 2 KPtF6 + 2 O2 + IF7
Reactions
Iodine heptafluoride decomposes at 200 °C to fluorine gas and iodine pentafluoride.[9]
Safety considerations
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.
References
- ↑ Macintyre, J. E. (Ed.). (1992). Dictionary of Inorganic Compounds (Vol. 3). London: Chapman & Hall.
- ↑ O'Neil, Maryadele J. (Ed.). (2001). The Merck Index (13th ed.). Whitehouse Station, NJ: Merck.
- ↑ Template:Cite journal
- ↑ Template:Cite journal
- ↑ Lide, David R. (2011). The CRC Handbook of Chemistry and Physics, 89th ed. p. 4-67.
- ↑ Template:Harvnb: "Das reine Jod-7-fluorid ist bei Zimmertemperatur ein farbloses Gas, das an der Luft infolge seiner Umsetzung mit dem Wasserdampf Nebel bildet und muffig sauer riecht. Beim Abkühlen wird es je nach den Versuchsbedingungen als leicht bewegliche, farblose Flüssigkeit als schneeweißes lockeres Pulver oder in Form farbloser Kristalle erhalten....Die Schmelztemperatur wurde durch Eintauchen von Proben, die in Quarzröhrchen eingeschmolzen waren, in Bäder passender Temperatur ermittelt und zu 5 bis 6° C gefunden. [Durch] Messung der Dampfdrucke...gelangt man zu der Gleichung ....Für den Druck von 760 mm errechnet sich eine Temperatur von 4,5° C. [Pure iodine heptafluoride is at room temperature a colorless gas, which forms a fog in air on account of its reaction with the humidity and smells musty and acrid. When cooled, it takes the form, depending on experimental conditions, of a free-flowing colorless liquid, a loose snow-white powder, or colorless crystals....The melting point was measured by immersion of a probe in a bath of the right temperature, which was melting in a little quartz tube and found to be 5Template:Nbh6 °C. [From] measurement of the vapor pressure...one arrives at the equation ....For a pressure of 760 mm it computes a temperature of 4.5 °C.]"
- ↑ Template:Cite journal
- ↑ Template:Cite book
- ↑ Template:Cite book