Mercury(I) fluoride
Mercury(I) fluoride
IUPAC name
Dimercury difluoride
Other names
Mercury(I) fluoride
Mercurous fluoride
3D model (JSmol)
ECHA InfoCard 100.034.302 Edit this at Wikidata
EC Number
  • 237-747-9
  • InChI=1S/2FH.2Hg/h2*1H;;/q;;2*+1/p-2
  • F[Hg][Hg]F
Molar mass 439.177 g/mol
Appearance yellow cubic crystals
Density 8.73 g/cm3, solid
−26.5·10−6 cm3/mol
GHS labelling:
GHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard
H300, H310, H330, H373, H410
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
Flash point non-flammable
Related compounds
Other anions
Mercury(I) chloride
Mercury(I) bromide
Mercury(I) iodide
Other cations
Zinc fluoride
Cadmium fluoride
Related compounds
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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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.[1]


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

Hg2CO3 + 2 HF → Hg2F2 + CO2 + H2O


When added to water, mercury(I) fluoride hydrolyzes to elemental liquid mercury, mercury(II) oxide, and hydrofluoric acid:[1]

Hg2F2 + H2O → Hg + HgO + 2 HF

It can be used in the Swarts reaction to convert alkyl halides into alkyl fluorides:[4]

2 R-X + Hg2F2 → 2 R-F + Hg2X2
where X = Cl, Br, I


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.[5] 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.[5] The compound is often formulated as Hg2+


  1. ^ a b c Perry, Dale L.; Phillips, Sidney L. (1995), Handbook of Inorganic Compounds, CRC Press, p. 256, ISBN 0-8493-8671-3, retrieved 2008-06-17
  2. ^ John Rumble (June 18, 2018). CRC Handbook of Chemistry and Physics (99 ed.). CRC Press. pp. 5–189. ISBN 978-1138561632.
  3. ^ 339318 Mercury(I) fluoride technical grade, Sigma-Aldrich, retrieved 2008-06-17
  4. ^ Beyer, Hans; Walter, Wolfgang; Lloyd, Douglas (1997), Organic Chemistry, Horwood Publishing, p. 136, ISBN 1-898563-37-3, retrieved 2008-06-17
  5. ^ a b Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  6. ^ Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5