|Jmol-3D images||Image 1|
|Molar mass||209.93 g/mol|
|Appearance||white crystals or colorless liquid
|Melting point||17.5 °C|
|Boiling point||34.0 °C|
|Solubility in water||hydrolyzes|
|Crystal structure||Orthorhombic, oP28|
|Space group||Pnma, No. 62|
|Other cations||Tungsten hexafluoride
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Molybdenum hexafluoride, also molybdenum(VI) fluoride, (MoF6) is the highest fluoride of molybdenum. It is a solid which melts just below room temperature; in water, it hydrolyses to give hydrofluoric acid. It is one of the seventeen known binary hexafluorides.
- Mo + 3 F
2 → MoF
Molybdenum hexafluoride is a liquid at room temperature. At 17.5 °C, it freezes into a white crystalline solid. The boiling point is 34.0 °C.
The solid structure measured at −140 °C is orthorhombic space group Pnma. Lattice parameters are a = 9.394 Å, b = 8.543 Å, and c = 4.959 Å. There are four formula units (in this case, discrete molecules) per unit cell, giving a density of 3.50 g·cm−3. The fluorine atoms are arranged in the hexagonal close packing.
Molybdenum hexafluoride has few uses, and generally appears as an impurity in uranium hexafluoride (in the nuclear industry, since molybdenum is a fission product of uranium) or tungsten hexafluoride (in the semiconductor industry; WF6 is used for chemical vapour deposition of tungsten, and MoF6 appears due to the chemical similarity of molybdenum and tungsten); it can be removed from the latter by reduction of a WF6-MoF6 mixture with any of a number of elements including molybdenum at moderately elevated temperature.
- This article incorporates information from the German Wikipedia.
- CRC Handbook of Chemistry and Physics, 90th Edition, CRC Press, Boca Raton, Florida, 2009, ISBN 978-1-4200-9084-0, 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; doi:10.1021/ic052029f; PMID 16634614
- Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419.
- J. H. Levy, J. C Taylor, A. B. Waugh: "Neutron Powder Structural Studies of UF6, MoF6 and WF6 at 77 K", in: Journal of Fluorine Chemistry, 1983, 23 (1), pp. 29–36; doi:10.1016/S0022-1139(00)81276-2.
- US-Patent 5234679: Method of Refining Tungsten Hexafluoride Containing Molybdenum Hexafluoride as an Impurity, 10 August 1993.
- US-Patent 6896866: Method for Purification of Tungsten Hexafluoride, 24 May 2005.