Silver(II) fluoride is a
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the
formulaA chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
AgF
2. It is a rare example of a silver(II) compound. Silver is usually present in its +1
oxidation stateIn chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
. It is used as a fluorinating agent.
AgF
2 can be synthesized by fluorinating Ag
2O with elemental
fluorineFluorine is the chemical element with atomic number 9, represented by the symbol F. Fluorine forms a single bond with itself in elemental form, resulting in the diatomic F
2 molecule. F
2 is a supremely reactive, poisonous, pale, yellowish brown gas. Elemental fluorine is the...
. Also, at 200 °C (473 K) elemental fluorine will react with
AgFSilver fluoride , also known as argentous fluoride and silver monofluoride, is a compound of silver and fluorine. It is a ginger-coloured solid, melting point 435 °C, which blackens on exposure to moist air. Unlike other silver halides such as silver chloride it is soluble in water to the extent...
or AgCl to produce AgF
2.
As a strong fluorinating agent, AgF
2 should be stored in Teflon or a passivated metal container.
Silver(II) fluoride is a
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the
formulaA chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
AgF
2. It is a rare example of a silver(II) compound. Silver is usually present in its +1
oxidation stateIn chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
. It is used as a fluorinating agent.
Preparation
AgF
2 can be synthesized by fluorinating Ag
2O with elemental
fluorineFluorine is the chemical element with atomic number 9, represented by the symbol F. Fluorine forms a single bond with itself in elemental form, resulting in the diatomic F
2 molecule. F
2 is a supremely reactive, poisonous, pale, yellowish brown gas. Elemental fluorine is the...
. Also, at 200 °C (473 K) elemental fluorine will react with
AgFSilver fluoride , also known as argentous fluoride and silver monofluoride, is a compound of silver and fluorine. It is a ginger-coloured solid, melting point 435 °C, which blackens on exposure to moist air. Unlike other silver halides such as silver chloride it is soluble in water to the extent...
or AgCl to produce AgF
2.
As a strong fluorinating agent, AgF
2 should be stored in Teflon or a passivated metal container. It is light sensitive.
AgF
2 can be purchased from various suppliers, the demand being less than 100 kg/year. While laboratory experiments find use for AgF
2, it is too expensive for large scale industry use. In 1993, AgF
2 cost between 1000-1400 US dollars per kg.
Composition and structure
AgF
2 is a white crystalline powder, but it is usually black/brown due to impurities. The F/Ag ratio for most samples is< 2, typically approaching 1.75 due to contamination with
AgSilver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
and
oxidesOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
and
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
.
For some time, it was doubted silver was actually in the 2+ oxidation state rather in some combination of states such as Ag
I[Ag
IIIF
4], which would be similar to silver oxide.
Neutron diffractionNeutron diffraction is a method for the determination of the atomic and/or magnetic structure of a material. It can be equally well applied to study crystalline solids , gasses, liquids or amorphous materials. Neutron diffraction is a form of elastic scattering where the neutrons exiting the...
studies, however, confirmed its description as silver(II). The Ag
I[Ag
IIIF
4] was found to be present at high temperatures, but it was unstable with respect to AgF
2.
In the gas phase, AgF
2 is believed to have D
∞h symmetryThe symmetry group of an object is the group of all isometries under which it is invariant with composition as the operation...
.
Approximately 14 kcal/
molThe mole is a unit of amount of substance: it is an SI base unit, and one of the few units used to measure this physical quantity. The name "mole" was coined in German by Wilhelm Ostwald in 1893, although the related concept of equivalent mass had been in use at least a century earlier...
(59 kJ/mol) separate the ground and first
stateExcitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being excited to an excited state....
s. The compound is paramagnetic, but it becomes ferromagnetic at temperatures below −110 °C (163 K).
Uses
AgF
2 is a strong fluorinating and oxidation agent. Illustrative applications are listed below.
- Fluoronation and preparation of organic perfluorocompounds
This type of reaction can occur in three different ways (here Z refers to any element or group attached to carbon, X is a
halogenThe halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine, ; chlorine, ; bromine, ; iodine, ; and astatine,...
):
- 1) CZ3H + 2 AgF2 → CZ3F +HF + 2 AgF
- 2) CZ3X + 2AgF2 → CZ3F +X2 + 2 AgF
- 3) Z2C=CZ2 + 2 AgF2 → Z2CFCFZ2 + 2 AgF
Similar transformations can also be effected using other high
valenceIn chemistry, valence, also known as valency or valency number, is a measure of the number of chemical bonds formed by the atoms of a given element...
metallic fluorides such as
CoF3Cobalt fluoride is the chemical compound with the formula CoF3. This highly reactive, hygroscopic brown solid is used to synthesize organofluorine compounds. CoF3 is a powerful fluorinating agent, the product being CoF2...
, MnF
3, CeF
4, and PbF
4.
- Fluorinations of aromatic compounds is readily achieved, but selective monofluorinations are more difficult:
- C6H6 + 2 AgF2 → C6H5F + 2 AgF + HF
- Oxidation of xenon
Xenon is a chemical element represented by the symbol Xe. Its atomic number is 54. A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
. This reaction, which can be explosive, proceeds in anhydrousAs a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another.-Solvents:...
HF solutions producing XeF2.
- AgF2 oxidizes carbon monoxide
Carbon monoxide is a colorless, odorless and tasteless gas, yet very toxic to humans. It consists of one carbon atom and one oxygen atom, connected by a covalent double bond and a dative covalent bond...
to carbonyl fluorideCarbonyl fluoride is the chemical compound with the formula COF2. This gas, like its analogue phosgene, is highly toxic. The molecule is planar with C2v symmetry.-Safety:...
.
External links