Molybdenum hexafluoride
Molybdenum hexafluoride, also molybdenum 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 [Molybdenum difluoride dioxide|] and [Molybdenum oxytetrafluoride|].
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 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 [Tungsten hexafluoride|]- mixture with any of a number of elements including hydrogen iodide at moderately elevated temperature.