Rhenium hexafluoride, also rhenium(VI) fluoride, (ReF
6) is a compound of
rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-gray, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is on ...
and
fluorine 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 ...
s.
Synthesis
Rhenium hexafluoride is made by combining
rhenium heptafluoride
Rhenium heptafluoride is the compound with the formula ReF7. It is a yellow low melting solid and is the only thermally stable metal heptafluoride. It has a distorted pentagonal bipyramidal structure similar to IF7, which was confirmed by neutron ...
with additional rhenium metal at 300 °C in a
pressure vessel
A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.
Construction methods and materials may be chosen to suit the pressure application, and will depend on the size o ...
.
:6 + Re → 7
Description
Rhenium hexafluoride is a liquid at room temperature. At 18.5 °C, it freezes into a yellow solid. The boiling point is 33.7 °C.
The solid structure measured at −140 °C is
orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with ...
space group ''Pnma''.
Lattice parameters are ''a'' = 9.417
Å, ''b'' = 8.570 Å, and ''c'' = 4.965 Å. There are four
formula unit
In chemistry, a formula unit is the empirical formula of any ionic or covalent network solid compound used as an independent entity for stoichiometric calculations. It is the lowest whole number ratio of ions represented in an ionic compound. ...
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, for example) does not necessari ...
, giving a density of 4.94 g·cm
−3.
The ReF
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 ...
, which has point group (''
Oh''). The Re–F
bond length
In molecular geometry, bond length or bond distance is defined as the average distance between nuclei of two bonded atoms in a molecule. It is a transferable property of a bond between atoms of fixed types, relatively independent of the rest ...
is 1.823 Å.
Use
Rhenium hexafluoride is a commercial material used in the electronics industry for
depositing films of rhenium.
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 103rd edition, published in 2022. It is sometimes nicknamed the "Rubber Bible ...
'', 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 synthesis and behavior of inorganic and organometallic compounds. This field covers chemical compounds that are not carbon-based, which are the subjects of organic chemistry. The distinction between the two disc ...
'', 2006, ''45 (9)'', S. 3782–3788; ; .
Further reading
* ''
Gmelins Handbuch der anorganischen Chemie'', System Nr. 70, Rhenium, Part A, pp. 102–105.
External links
Rhenium hexafluoride at webelements.com
{{Rhenium compounds
Rhenium compounds
Hexafluorides
Octahedral compounds