Arsenic pentafluoride (AsF5)

Structure and bonding

AsF5 adopts a trigonal bipyramidal geometry with five As–F bonds; two positions are axial and three are equatorial. The arsenic center is in the formal +5 oxidation state, making the molecule electron-poor and able to accept electron pairs from donors. The distinct axial and equatorial contacts lead to slightly different bond environments and reactivity at those sites.

Preparation and reactions

The compound is prepared commercially and in the laboratory by direct fluorination of arsenic or by oxidation/fluorination of lower-valent arsenic fluorides. AsF5 hydrolyzes readily in the presence of water to give arsenic oxides and hydrogen fluoride, and it reacts with fluoride donors to form salts containing the hexafluoroarsenate anion (AsF6−).

Uses and applications

In research and industrial contexts AsF5 serves as a powerful Lewis acid and fluorinating agent. It is used to generate non-coordinating anions and to stabilize cationic species in studies of inorganic and organometallic chemistry. The ability to form five arsenic–fluorine bonds and to accept additional fluoride is central to its role in producing hexafluoroarsenate salts and related complexes.

Safety and handling

AsF5 is highly toxic, corrosive, and reacts with moisture to produce hydrogen fluoride and toxic arsenic-containing products. Handling requires specialized fluorine-compatible materials, containment, and trained personnel. Exposure risks and waste disposal demand strict regulatory and laboratory controls.

Context and related compounds

Arsenic pentafluoride belongs to the group 15 pentafluorides alongside phosphorus and antimony analogues and shares characteristics with agents such as SbF5. It is of interest for fundamental studies of bonding, Lewis acidity, and the chemistry of highly fluorinated anions. For further chemical properties and safety details see sources and databases: compound entry, elemental context, halogen chemistry, and specific reagent guides at oxidation-state references and anion formation notes.