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 at760 mmHg: instead, the compound begins tosublime at 4.77 °C. The dense vapor has a mouldy, acrid odour.[6][7]
IF7 is prepared by passingF2 through liquidIF5 at 90 °C, then heating the vapours to 270 °C. Alternatively, this compound can be prepared from fluorine and driedpalladium orpotassium iodide to minimize the formation of IOF5, an impurity arising by hydrolysis.[8][9] Iodine heptafluoride is also produced as a by-product whendioxygenyl hexafluoroplatinate is used to prepare other platinum(V) compounds such aspotassium hexafluoroplatinate(V), usingpotassium fluoride in iodine pentafluoride solution:[10]
^Ruff & Keim 1930, pp. 180–182: "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 5‑6 °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.]"
Ruff, Otto; Keim, Rudolf (1930-10-21). "Das Jod-7-fluorid" [Iodine Heptafluoride].Zeitschrift für anorganische und allgemeine Chemie (in German).193 (1/2):176–186.doi:10.1002/zaac.19301930117.ISSN0863-1786.
