Silver(II) fluoride
Encyclopedia
Silver fluoride is a chemical compound
with the formula
AgF2. It is a rare example of a silver(II) compound. Silver
is usually present in its +1 oxidation state
. It is used as a fluorinating agent.
. Also, at 200 °C (473 K) elemental fluorine will react with AgF
or AgCl to produce AgF2.
As a strong fluorinating agent, AgF2 should be stored in Teflon or a passivated metal container. It is light sensitive.
AgF2 can be purchased from various suppliers, the demand being less than 100 kg/year. While laboratory experiments find use for AgF2, it is too expensive for large scale industry use. In 1993, AgF2 cost between 1000-1400 US dollars per kg.
and oxides
and carbon
.
For some time, it was doubted silver was actually in the +2 oxidation state rather in some combination of states such as AgI[AgIIIF4], which would be similar to silver(I,III) oxide. Neutron diffraction
studies, however, confirmed its description as silver(II). The AgI[AgIIIF4] was found to be present at high temperatures, but it was unstable with respect to AgF2.
In the gas phase, AgF2 is believed to have D∞h symmetry
.
Approximately 14 kcal/mol
(59 kJ/mol) separate the ground
and first state
s. The compound is paramagnetic, but it becomes ferromagnetic at temperatures below −110 °C (163 K).
of gaseous reactions with fluorine by silver. With fluoride ions, it forms complex ions such as , the blue-violet , and .
It is used in the fluorination 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 halogen
):
Similar transformations can also be effected using other high valence
metallic fluorides such as CoF3
, MnF3, CeF4, and PbF4.
is also used in the fluorination of aromatic compounds, although selective monofluorinations are more difficult:
oxidises xenon
to xenon difluoride
in anhydrous
HF solutions.
It also oxidises carbon monoxide
to carbonyl fluoride
.
It reacts with water to form oxygen gas:
, oxidizes iodide
to iodine
, and upon contact with acetylene
forms the contact explosive silver acetylide
. It is light-sensitive, very hygroscopic and corrosive. It decomposes violently on contact with hydrogen peroxide
, releasing oxygen gas. It also liberates HF
and .
Chemical compound
A 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 formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
AgF2. It is a rare example of a silver(II) compound. Silver
Silver
Silver is a metallic 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...
is usually present in its +1 oxidation state
Oxidation state
In 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
AgF2 can be synthesized by fluorinating Ag2O with elemental fluorineFluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
. Also, at 200 °C (473 K) elemental fluorine will react with AgF
Silver(I) fluoride
Silver 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 AgF2.
As a strong fluorinating agent, AgF2 should be stored in Teflon or a passivated metal container. It is light sensitive.
AgF2 can be purchased from various suppliers, the demand being less than 100 kg/year. While laboratory experiments find use for AgF2, it is too expensive for large scale industry use. In 1993, AgF2 cost between 1000-1400 US dollars per kg.
Composition and structure
AgF2 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
Silver is a metallic 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 oxides
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
and carbon
Carbon
Carbon 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 AgI[AgIIIF4], which would be similar to silver(I,III) oxide. Neutron diffraction
Neutron diffraction
Neutron diffraction or elastic neutron scattering is the application of neutron scattering to the determination of the atomic and/or magnetic structure of a material: A sample to be examined is placed in a beam of thermal or cold neutrons to obtain a diffraction pattern that provides information of...
studies, however, confirmed its description as silver(II). The AgI[AgIIIF4] was found to be present at high temperatures, but it was unstable with respect to AgF2.
In the gas phase, AgF2 is believed to have D∞h symmetry
Symmetry group
The symmetry group of an object is the group of all isometries under which it is invariant with composition as the operation...
.
Approximately 14 kcal/mol
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
(59 kJ/mol) separate the ground
Ground state
The ground state of a quantum mechanical system is its lowest-energy state; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state...
and first state
Excited state
Excitation 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
AgF2 is a strong fluorinating and oxidising agent. It is formed as an intermediate in the catalysisCatalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
of gaseous reactions with fluorine by silver. With fluoride ions, it forms complex ions such as , the blue-violet , and .
It is used in the fluorination 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 halogen
Halogen
The 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...
):
- CZ3H + 2 AgF2 → CZ3F +HF + 2 AgF
- CZ3X + 2AgF2 → CZ3F +X2 + 2 AgF
- Z2C=CZ2 + 2 AgF2 → Z2CFCFZ2 + 2 AgF
Similar transformations can also be effected using other high valence
Valence (chemistry)
In chemistry, valence, also known as valency or valence number, is a measure of the number of bonds formed by an atom of a given element. "Valence" can be defined as the number of valence bonds...
metallic fluorides such as CoF3
Cobalt(III) fluoride
Cobalt fluoride is the inorganic compound with the formula CoF3. This highly reactive, hygroscopic brown solid is used to synthesize organofluorine compounds...
, MnF3, CeF4, and PbF4.
is also used in the fluorination of aromatic compounds, although selective monofluorinations are more difficult:
- C6H6 + 2 AgF2 → C6H5F + 2 AgF + HF
oxidises xenon
Xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced or . A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
to xenon difluoride
Xenon difluoride
Xenon difluoride is a powerful fluorinating agent with the chemical formula , and one of the most stable xenon compounds. Like most covalent inorganic fluorides it is moisture sensitive. It decomposes on contact with light or water vapour. Xenon difluoride is a dense, white crystalline solid. It...
in anhydrous
Anhydrous
As 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...
HF solutions.
- 2 AgF2 + Xe → 2 AgF + XeF2
It also oxidises carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
to carbonyl fluoride
Carbonyl fluoride
Carbonyl fluoride is the chemical compound with the formula COF2. This gas, like its analog phosgene, is highly toxic. The molecule is planar with C2v symmetry.-Safety:...
.
- 2 AgF2 + CO → 2 AgF + COF2
It reacts with water to form oxygen gas:
- 4 AgF2 + 4 H2O → 2 Ag2O + 8 HF + O2
Safety
is a very strong oxidizer that reacts violently with water, reacts with dilute acids to produce ozoneOzone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
, oxidizes iodide
Iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...
to iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
, and upon contact with acetylene
Acetylene
Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...
forms the contact explosive silver acetylide
Silver acetylide
Silver acetylide is an inorganic chemical compound with the formula Ag2C2, a metal acetylide. The name is derived from the way it is synthesized, and emphasizes that the compound can be regarded as a salt of the weak acid, acetylene. Since acetylene is called "ethyne" in the modern IUPAC...
. It is light-sensitive, very hygroscopic and corrosive. It decomposes violently on contact with hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
, releasing oxygen gas. It also liberates HF
Hydrogen fluoride
Hydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...
and .