Mercury(II) fluoride is a chemical compound made up of mercury and fluorine atoms with chemical formula . It is produced by the reaction of mercury(II) oxide and hydrogen fluoride, and is usually encountered as the hydrated form . It is used as a fluorinating agent in organic chemistry.
Synthesis
Mercury(II) fluoride is most commonly produced by the reaction of mercury(II) oxide and hydrogen fluoride: HgO + 2 HF → HgF2 + H2O
Mercury(II) fluoride can also be produced through the fluorination of mercury(II) chloride: HgCl2 + F2 → HgF2 + Cl2
or of mercury(II) oxide: 2 HgO + 2 F2 → 2 HgF2 + O2 with oxygen as byproduct.
Hydrates
Mercury(II) fluoride normally exists in the form of the dihydrate, .
Structure
Under ambient conditions, anhydrous mercury(II) fluoride adopts the fluorite structure, like many other compounds of composition (M = metal). This type of structure is cubic, with each atom of mercury being surrounded by 8 fluorine atoms in a cubic configuration, and each atom of fluorine being surrounded by 4 mercury atoms in a tetrahedral configuration. At high pressures, however, it undergoes a phase transition, starting at 2.5 GPa and being completed at 4.7 GPa, to a cotunnite-type structure, which is monoclinic. This structure persists to at least 63 GPa.
The dihydrate adopts an orthorhombic structure.
Reactions and applications
In water, mercury(II) fluoride almost completely decomposes.
At high pressure, mercury(II) fluoride is predicted to react with fluorine or xenon difluoride to form mercury(IV) fluoride.
Mercury(II) fluoride is a selective fluorination agent. It has been found to be effective at many of the same reactions that silver fluoride or mercury(I) fluoride are, such as the fluorination of organobromine or organoiodine compounds, with higher yields and reduced reaction times. It has also been found to fluorinate triphenylacetic acid, triphenyl ethylene, and triethyl phosphite.
References