Mercury(I) fluoride


Mercury fluoride or mercurous fluoride is the chemical compound composed of mercury and fluorine with the formula Hg2F2. It consists of small yellow cubic crystals, which turn black when exposed to light.

Synthesis

Mercury fluoride is prepared by the reaction of mercury carbonate with hydrofluoric acid:

Reactions

When added to water, mercury fluoride hydrolyzes to elemental liquid mercury, mercury oxide, and hydrofluoric acid:
It can be used in the Swarts reaction to convert alkyl halides into alkyl fluorides:

Structure

In common with other Hg compounds which contain linear X-Hg-Hg-X units, Hg2F2 contains linear FHg2F units with an Hg-Hg bond length of 251 pm and an Hg-F bond length of 214 pm. The overall coordination of each Hg atom is a distorted octahedron; in addition to the bonded F and other Hg of the molecule, there are four other F atoms at 272 pm. The compound is often formulated as Hg22+ 2F−.