Molybdenum hexafluoride
{{chembox
|Verifiedfields = changed
|Watchedfields = changed
|verifiedrevid = 428735896
|Name = Molybdenum hexafluoride
|ImageFile = Molybdenum(VI)-fluoride.svg
|ImageFile1 = Molybdenum-hexafluoride-from-xtal-3D-SF.png
|ImageSize = 150px
|ImageClass = skin-invert-image
|ImageClass1 = bg-transparent
|IUPACNames = molybdenum(VI) fluoride
|OtherNames = molybdenum hexafluoride
|Section1 = {{Chembox Identifiers
|CASNo_Ref = {{cascite|correct|??}}
|CASNo = 7783-77-9
|ChemSpiderID = 74199
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = ZLT5J123W3
|PubChem = 82219
|EINECS = 232-026-5
|InChI = 1S/6FH.Mo/h6*1H;/q;;;;;;+6/p-6
|SMILES = F[Mo](F)(F)(F)(F)F
}}
|Section2 = {{Chembox Properties
|Formula = {{chem2|MoF6}}
|Appearance = white crystalsCRC 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. or colorless liquid
hygroscopic
|Mo=1|F=6
|Density = 3.50 g/cm3T. 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}}
|Solubility = hydrolyzes
|MeltingPtC = 17.5
|BoilingPtC = 34.0
|MagSus = −26.0·10−6 cm3/mol
}}
|Section3 = {{Chembox Structure
|CrystalStruct = Orthorhombic, oP28
|SpaceGroup = Pnma, No. 62
|Coordination = octahedral (Oh)
|Dipole = 0
}}
|Section4 = {{Chembox Related
|OtherCations = {{ubl|Chromium hexafluoride|Tungsten hexafluoride|Uranium hexafluoride|Molybdenum(VI) chloride|Molybdenum(V) fluoride|Molybdenum(IV) fluoride}}
}}
}}
Molybdenum hexafluoride, also molybdenum(VI) fluoride, is an inorganic compound with the formula {{chem2|MoF6|auto=1}}. It is the fluoride of molybdenum in its highest oxidation state of +6. It is a colourless solid that melts just below room temperature and boils at 34 °C.{{Greenwood&Earnshaw}} It is one of the seventeen known binary hexafluorides.
Synthesis
Molybdenum hexafluoride is made by direct reaction of molybdenum metal in an excess of elemental fluorine:
:{{chem2|Mo + 3 F2 → MoF6}}
The compound hydrolyzes easily,{{Kirk-Othmer|doi=10.1002/0471238961.1315122513051908.a01|title=Fluorine compounds, inorganic, molybdenum|first1=Dayal T.|last1=Meshri|year=2000}} and typical impurities are Molybdenum difluoride dioxide and Molybdenum oxytetrafluoride.W. Kwasnik "Molybdenum(VI) Fluoride" Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 259.
Description
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. The fluorine atoms are arranged in the hexagonal close packing.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}}.
In liquid and gas phase, {{chem2|MoF6}} adopt octahedral molecular geometry with point group Oh. The Mo–F bond length is 1.817 Å.
Applications
Molybdenum hexafluoride has few uses. In the nuclear industry, {{chem2|MoF6}} occurs as an impurity in uranium hexafluoride since molybdenum is a fission product of uranium.
The semiconductor industry constructs various integrated circuits through chemical vapor deposition of molybdenum hexafluoride. In some cases, the deposited molybdenum is an impurity in the intended tungsten hexafluoride. {{chem2|MoF6}} can be removed by reduction of a Tungsten hexafluoride-{{chem2|MoF6}} mixture with any of a number of elements including hydrogen iodide at moderately elevated temperature.US-Patent 5234679: [http://www.patentstorm.us/patents/5234679/description.html Method of Refining Tungsten Hexafluoride Containing Molybdenum Hexafluoride as an Impurity] {{webarchive|url=https://web.archive.org/web/20110612111424/http://www.patentstorm.us/patents/5234679/description.html |date=2011-06-12}}, 10 August 1993US-Patent 6896866: [http://www.patentstorm.us/patents/6896866/description.html Method for Purification of Tungsten Hexafluoride] {{webarchive|url=https://web.archive.org/web/20110612111437/http://www.patentstorm.us/patents/6896866/description.html |date=2011-06-12}}, 24 May 2005.
References
{{reflist}}
{{Hexafluorides}}
{{Molybdenum compounds}}
{{fluorides}}