Iridium hexafluoride, also iridium(VI) fluoride, (IrF
6) is a compound of
iridium
Iridium is a chemical element; it has the symbol Ir and atomic number 77. This very hard, brittle, silvery-white transition metal of the platinum group, is considered the second-densest naturally occurring metal (after osmium) with a density ...
and
fluorine
Fluorine is a chemical element; it has Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard temperature and pressure, standard conditions as pale yellow Diatomic molecule, diatomic gas. Fluorine is extre ...
and one of the seventeen known binary
hexafluoride A hexafluoride is a chemical compound with the general formula QXnF6, QXnF6m−, or QXnF6m+. Many molecules fit this formula. An important hexafluoride is hexafluorosilicic acid (H2SiF6), which is a byproduct of the mining of phosphate rock. In t ...
s. It is one of only a few compounds with iridium in the
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...
+6.
Synthesis
Iridium hexafluoride is made by a direct reaction of iridium metal in an excess of elemental
fluorine
Fluorine is a chemical element; it has Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard temperature and pressure, standard conditions as pale yellow Diatomic molecule, diatomic gas. Fluorine is extre ...
gas at 300 °C. However, it is thermally unstable and must be frozen out of the gaseous reaction mixture to avoid dissociation.
: + 3 →
Description
Iridium hexafluoride is a yellow crystalline solid that melts at 44 °C and boils at 53.6 °C.
The solid structure measured at −140 °C is
orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...
space group ''Pnma''.
Lattice parameters are ''a'' = 9.411
Å, ''b'' = 8.547 Å, and ''c'' = 4.952 Å. There are four
formula unit
In chemistry, a formula unit is the smallest unit of a non-molecular substance, such as an ionic compound, covalent network solid, or metal. It can also refer to the chemical formula for that unit. Those structures do not consist of discrete mol ...
s (in this case, discrete molecules) per
unit cell
In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector
In mathematics, a unit vector i ...
, giving a density of 5.11 g·cm
−3.
The IrF
6 molecule itself (the form important for the liquid or gas phase) has
octahedral molecular geometry
In chemistry, octahedral molecular geometry, also called square bipyramidal, describes the shape of compounds with six atoms or groups of atoms or ligands symmetrically arranged around a central atom, defining the vertices of an octahedron. The o ...
, which has point group (''
Oh''). The Ir–F
bond length
In molecular geometry, bond length or bond distance is defined as the average distance between Atomic nucleus, nuclei of two chemical bond, bonded atoms in a molecule. It is a Transferability (chemistry), transferable property of a bond between at ...
is 1.833 Å.
Calculations suggest that
fluorine
Fluorine is a chemical element; it has Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard temperature and pressure, standard conditions as pale yellow Diatomic molecule, diatomic gas. Fluorine is extre ...
might react with iridium hexafluoride at 39 GPa to form IrF
8.
References
['']CRC Handbook of Chemistry and Physics
The ''CRC Handbook of Chemistry and Physics'' is a comprehensive one-volume reference resource for science research. First published in 1914, it is currently () in its 105th edition, published in 2024. It is known colloquially among chemists as ...
'', 90th Edition, CRC Press, Boca Raton, Florida, 2009, , Section 4, ''Physical Constants of Inorganic Compounds'', p. 4-85.
[T. Drews, J. Supeł, A. Hagenbach, K. Seppelt: "Solid State Molecular Structures of Transition Metal Hexafluorides", in: '']Inorganic Chemistry
Inorganic chemistry deals with chemical synthesis, synthesis and behavior of inorganic compound, inorganic and organometallic chemistry, organometallic compounds. This field covers chemical compounds that are not carbon-based, which are the subj ...
'', 2006, ''45 (9)'', S. 3782–3788; ; .
Further reading
* ''
Gmelins Handbuch der anorganischen Chemie
The Gmelin database is a large database of organometallic and inorganic compounds updated quarterly. It is based on the German publication ''Gmelins Handbuch der anorganischen Chemie'' ("Gmelin's Handbook of Inorganic Chemistry") which was original ...
'', System Nr. 67, Iridium, Supplement Volume 2, pp. 99–102.
External links
Iridium hexafluoride at webelements.com
{{fluorine compounds
Iridium compounds
Hexafluorides
Platinum group halides
Octahedral compounds