Molybdenum hexafluoride

Molybdenum hexafluoride, also molybdenum(VI) fluoride, is an inorganic compound with the formula MoF₆. 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.^[3] It is one of the seventeen known binary hexafluorides.

Molybdenum hexafluoride

Names
IUPAC names molybdenum(VI) fluoride
Other names molybdenum hexafluoride
Identifiers
CAS Number	7783-77-9 Y
3D model (JSmol)	Interactive image
ChemSpider	74199
ECHA InfoCard	100.029.114
EC Number	232-026-5
PubChem CID	82219
UNII	ZLT5J123W3 Y
CompTox Dashboard (EPA)	DTXSID0064834
InChI InChI=1S/6FH.Mo/h6*1H;/q;;;;;;+6/p-6
SMILES F[Mo](F)(F)(F)(F)F
Properties
Chemical formula	MoF6
Molar mass	209.94 g·mol−1
Appearance	white crystals[1] or colorless liquid hygroscopic
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]
Solubility in water	hydrolyzes
Magnetic susceptibility (χ)	−26.0·10−6 cm3/mol
Structure
Crystal structure	Orthorhombic, oP28
Space group	Pnma, No. 62
Coordination geometry	octahedral (Oh)
Dipole moment	0
Related compounds
Other cations	Chromium hexafluoride Tungsten hexafluoride Uranium hexafluoride Molybdenum(VI) chloride Molybdenum(V) fluoride Molybdenum(IV) fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Synthesis

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

Mo + 3 F₂ → MoF₆

The compound hydrolyzes easily,^[4] and typical impurities are MoO₂F₂ and MoOF₄.^[5]

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.^[2] The fluorine atoms are arranged in the hexagonal close packing.^[6]

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

Applications

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.

The semiconductor industry constructs various integrated circuits through chemical vapor deposition of molybdenum hexafluoride.^[4] In some cases, the deposited molybdenum is an impurity in the intended tungsten hexafluoride. MoF₆ can be removed by reduction of a WF₆-MoF₆ mixture with any of a number of elements including hydrogen iodide at moderately elevated temperature.^[7][8]