Mercury(I) fluoride

Mercury(I) fluoride

Mercury(I) fluoride
Names
IUPAC name Mercury(I) fluoride
Other names Mercurous fluoride
Identifiers
CAS Number	13967-25-4
Properties
Chemical formula	Hg2F2
Molar mass	439.177 g/mol
Appearance	yellow cubic crystals
Density	8.73 g/cm³, solid
Solubility in water	decomposes
Vapor pressure	{{{value}}}
Related compounds
Other anions	Mercury(I) chloride Mercury(I) bromide Mercury(I) iodide
Other cations	Zinc fluoride Cadmium fluoride Mercury(II) fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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

Hg₂CO₃ + 2 HF → Hg₂F₂ + CO₂ + H₂O

Reactions

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

Hg₂F₂ + H₂O → Hg + HgO + 2 HF

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

2 R-X + Hg₂F₂ → 2 R-F + Hg₂X₂

where X = Cl, Br, I

Structure

File:Unit cell of Hg2F2.png

Unit cell of Hg₂F2, with F from adjacent molecules coordinating the Hg atoms

In common with other Hg(I) (mercurous) compounds which contain linear X-Hg-Hg-X units, Hg₂F₂ contains linear FHg₂F 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 Hg₂²⁺ 2F⁻.