PF5

PF5, or phosphorus pentafluoride, is a volatile inorganic compound of phosphorus and fluorine. It is a colorless gas at room temperature and is highly reactive, particularly with moisture, so it is typically handled under strictly dry, inert conditions. It is widely used as a fluorinating reagent in inorganic and organic chemistry.

In terms of structure, PF5 features five fluorine ligands around a central phosphorus atom in a trigonal bipyramidal geometry. The molecule behaves as a strong Lewis acid and readily forms adducts with fluoride donors, such as producing PF6− in the presence of excess fluoride.

Reactivity and hazards: PF5 hydrolyzes rapidly in water, giving phosphoric acid and hydrogen fluoride, commonly summarized by the overall equation PF5 + 4 H2O → H3PO4 + 5 HF. It also reacts with alcohols, amines, and other nucleophiles, and it serves as a powerful reagent for introducing fluorine into substrates. In addition to hydrolysis, PF5 can generate related phosphorus oxyfluorides such as POF3 under certain conditions. Safety concerns are significant: PF5 is toxic and corrosive, and hydrolysis produces HF, a highly dangerous acid; appropriate handling under dry conditions and proper protective equipment are essential.

Production and applications: PF5 is produced by controlled fluorination of phosphorus-containing precursors. It is used primarily as a fluorinating agent in organic synthesis and as a starting material for the preparation of fluorinated phosphorus compounds and certain materials-processing applications.

See also: PF6−, POF3.