Mercury(I) fluoride or mercurous fluoride is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

composed of

mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

and

fluorine Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reacti ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

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 Hydrofluoric acid is a Solution (chemistry), solution of hydrogen fluoride (HF) in water. Solutions of HF are colourless, acidic and highly Corrosive substance, corrosive. It is used to make most fluorine-containing compounds; examples include th ...

: :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 Swarts fluorination is a process whereby the chlorine atoms in a compound – generally an organic compound, but experiments have been performed using silanes – are replaced with fluorine, by treatment with antimony trifluoride in the presence o ...

to convert alkyl halides into alkyl fluorides: :2 R-X + Hg₂F₂ → 2 R-F + Hg₂X₂ :where X = Cl, Br, I

Structure

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.Wells A.F. (1984) ''Structural Inorganic Chemistry'' 5th edition Oxford Science Publications 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⁻.

References

{{fluorine compounds Mercury(I) compounds Fluorides Metal halides