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Mercury(I) fluoride

Mercury(I) fluoride or mercurous fluoride is the chemical compound composed of mercury and fluorine with the formula Hg<sub>2</sub>F<sub>2</sub>. It consists of small yellow cubic crystals, which turn black when exposed to light.

Synthesis

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

Hg<sub>2</sub>CO<sub>3</sub> + 2 HF → Hg<sub>2</sub>F<sub>2</sub> + CO<sub>2</sub> + H<sub>2</sub>O

Reactions

When added to water, mercury(I) fluoride hydrolyzes to elemental liquid mercury, mercury(II) oxide, and hydrofluoric acid:

Hg<sub>2</sub>F<sub>2</sub> + H<sub>2</sub>O → Hg + HgO + 2 HF

It can be used in the Swarts reaction to convert alkyl halides into alkyl fluorides:

2 R-X + Hg<sub>2</sub>F<sub>2</sub> → 2 R-F + Hg<sub>2</sub>X<sub>2</sub>
where X = Cl, Br, I

Structure

In common with other Hg(I) (mercurous) compounds which contain linear X-Hg-Hg-X units, Hg<sub>2</sub>F<sub>2</sub> contains linear FHg<sub>2</sub>F units with an Hg-Hg bond length of 251 pm (Hg-Hg in the metal is 300 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 .

References