Molybdenum hexafluoride, also molybdenum(VI) fluoride, is an inorganic compound with the formula . 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. 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:
The compound hydrolyzes easily, and typical impurities are and .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.
In liquid and gas phase, 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, 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. can be removed by reduction of a - mixture with any of a number of elements including hydrogen iodide at moderately elevated temperature.US-Patent 5234679: Method of Refining Tungsten Hexafluoride Containing Molybdenum Hexafluoride as an Impurity , 10 August 1993US-Patent 6896866: Method for Purification of Tungsten Hexafluoride , 24 May 2005.
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