Iodine heptafluoride
Encyclopedia
Iodine heptafluoride, also known as iodine(VII) fluoride or even iodine fluoride, is an interhalogen compound with chemical formula I
F
7. It has an unusual pentagonal bipyramidal
structure, as predicted by VSEPR theory
. The molecule can undergo a pseudorotation
al rearrangement called the Bartell mechanism
, which is like the Berry mechanism
but for a hepta coordinated 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.
through liquid IF5
at 90 °C, then heating the vapours to 270 °C. Alternately, 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
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
F
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...
7. It has an unusual pentagonal bipyramidal
Pentagonal bipyramid molecular geometry
In chemistry, a pentagonal bipyramid is a molecular geometry with one atom at the centre with seven ligands at the corners of a pentagonal dipyramid. A perfect pentagonal bipyramid belongs to the molecular point group D5h ....
structure, as predicted by VSEPR theory
VSEPR theory
Valence shell electron pair repulsion theory is a model in chemistry used to predict the shape of individual molecules based upon the extent of electron-pair electrostatic repulsion. It is also named Gillespie–Nyholm theory after its two main developers...
. The molecule can undergo a pseudorotation
Pseudorotation
The IUPAC defines pseudorotation as "a conformational change resulting in a structure that appears to have been produced by rotation of the entire initial molecule and is superimposable on the initial one, unless different positions are distinguished by substitution or isotopic labeling...
al rearrangement called the Bartell mechanism
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 exchanges the axial atoms with one pair of the...
, which is like the Berry mechanism
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 for two of the equatorial ones. It is the most widely accepted mechanism for pseudorotation...
but for a hepta coordinated 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.
Preparation
IF7 is prepared by passing F2Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
through liquid IF5
Iodine pentafluoride
Iodine pentafluoride is an interhalogen compound with chemical formula IF5. It is a fluoride of iodine. It is a colourless or yellow liquid with a density of 3.250 g cm−3. It was first synthesized by Henri Moissan in 1891 by burning solid iodine in fluorine gas...
at 90 °C, then heating the vapours to 270 °C. Alternately, this compound can be prepared from fluorine and dried palladium or potassium iodide
Potassium iodide
Potassium iodide is an inorganic compound with the chemical formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic than sodium iodide, making it easier to work with...
to minimize the formation of IOF5, an impurity arising by hydrolysis.