hexafluorides

Hexafluorides are a class of chemical compounds in which six fluorine atoms are coordinated to a central atom, forming MF6 units. In many cases the central atom is a metal in the +6 oxidation state, and the idealized geometry is octahedral. This class includes several well-known binary hexafluorides, such as sulfur hexafluoride (SF6), tungsten hexafluoride (WF6), selenium hexafluoride (SeF6), tellurium hexafluoride (TeF6), and xenon hexafluoride (XeF6).

These species typically feature strong M–F bonds and high symmetry. SF6 is exceptionally stable and chemically inert under ordinary conditions, properties that underpin its use as an insulating gas in electrical equipment because of its high dielectric strength. Other hexafluorides, such as WF6, SeF6, TeF6, and XeF6, tend to be more reactive or volatile and find use in fluorination chemistry or materials synthesis; WF6 is widely utilized in chemical vapor deposition to produce tungsten films, for example. The heavier hexafluorides and xenon derivatives illustrate the diversity of this family, from stable industrial gases to reactive fluorinating agents.

Synthesis of MF6 compounds generally proceeds by direct fluorination of the element or of its oxides under controlled conditions, using fluorine or other fluorinating agents at elevated temperatures. SF6 is produced by reacting sulfur with fluorine; WF6, SeF6, and TeF6 are formed by fluorinating tungsten, selenium, and tellurium precursors, respectively.

Many hexafluorides are moisture sensitive and hydrolyze to form hydrogen fluoride and oxide or oxyfluoride species of the central element. SF6 is notable for its long-term stability, while other members can be reactive toward water and oxygen. Environmental considerations are especially pronounced for SF6, a potent greenhouse gas with a very high global warming potential.