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 one ...
and
fluorine and one of the seventeen known binary
hexafluorides.
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.
: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 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. E ...
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 necessaril ...
, 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, 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 of ...
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'', 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'', 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