Molybdenum hexafluoride

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Molybdenum hexafluoride
IUPAC names
molybdenum(VI) fluoride
Other names
molybdenum hexafluoride
3D model (JSmol)
ECHA InfoCard 100.029.114
EC Number 232-026-5
Molar mass 209.93 g/mol
Appearance white crystals[1] or colorless liquid
Density 3.50 g/cm3[2]
Melting point 17.5 °C (63.5 °F; 290.6 K)[1]
Boiling point 34.0 °C (93.2 °F; 307.1 K)[1]
−26.0·10−6 cm3/mol
Orthorhombic, oP28
Pnma, No. 62
octahedral (Oh)
Related compounds
Other cations
Tungsten hexafluoride
Uranium hexafluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Molybdenum hexafluoride, also molybdenum(VI) fluoride is the inorganic compound with the formula MoF6. It is the highest fluoride of molybdenum. A colourless solid, it melts just below room temperature.[3] It is one of the seventeen known binary hexafluorides.


Molybdenum hexafluoride is made by direct reaction of molybdenum metal in an excess of elemental fluorine:[2]

Mo + 3 F

Typical impurities are MoO2F2 and MoOF4, reflecting the tendency of the hexafluoride to hydrolyze.[4]


At −140 °C, it crystallizes in the 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.[2] The fluorine atoms are arranged in the hexagonal close packing.[5]

In liquid and gas phase, MoF6 adopt octahedral molecular geometry with point group Oh. The Mo–F bond length is 1.817 Å.[2]


Molybdenum hexafluoride has few uses. In the nuclear industry, MoF6 occurs as an impurity in uranium hexafluoride since molybdenum is a fission product of uranium. It is also an impurity in tungsten hexafluoride, which is used in the semiconductor industry. MoF6 can be removed by reduction of a WF6-MoF6 mixture with any of a number of elements including molybdenum at moderately elevated temperature.[6][7]


  1. ^ a b c 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.
  2. ^ a b c d 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
  3. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. ^ W. Kwasnik "Molybdenum(VI) Fluoride" Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 259.
  5. ^ 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.
  6. ^ US-Patent 5234679: Method of Refining Tungsten Hexafluoride Containing Molybdenum Hexafluoride as an Impurity Archived 2011-06-12 at the Wayback Machine, 10 August 1993.
  7. ^ US-Patent 6896866: Method for Purification of Tungsten Hexafluoride Archived 2011-06-12 at the Wayback Machine, 24 May 2005.