Silver(II) fluoride is a chemical compound 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 ...

AgF₂. It is a rare example of a silver(II) compound. Silver usually exists in its +1 oxidation state. It is used as a fluorinating agent.

Preparation

AgF₂ can be synthesized by fluorinating Ag₂O with elemental

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 ...

. 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.

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 Ag and

oxides An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...

and carbon. For some time, it was doubted that silver was actually in the +2 oxidation state, rather than some combination of states such as Ag^I g^IIIF₄ which would be similar to silver(I,III) oxide. Neutron diffraction studies, however, confirmed its description as silver(II). The Ag^I g^IIIF₄was 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 (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definit ...

. Approximately 14 kcal/ mol (59 kJ/mol) separate the

ground Ground may refer to: Geology * Land, the surface of the Earth not covered by water * Soil, a mixture of clay, sand and organic matter present on the surface of the Earth Electricity * Ground (electricity), the reference point in an electrical c ...

and first excited states. The compound is paramagnetic, but it becomes

ferromagnetic Ferromagnetism is a property of certain materials (such as iron) which results in a large observed magnetic permeability, and in many cases a large magnetic coercivity allowing the material to form a permanent magnet. Ferromagnetic materials ...

at temperatures below −110 °C (163 K).

Uses

AgF₂ is a strong fluorinating and oxidising agent. It is formed as an intermediate in the catalysis 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 The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group is ...

): # 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 or valency may refer to: Science * Valence (chemistry), a measure of an element's combining power with other atoms * Degree (graph theory), also called the valency of a vertex in graph theory * Valency (linguistics), aspect of verbs rel ...

metallic fluorides such as CoF₃, 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 to xenon difluoride in

anhydrous A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achie ...

HF solutions. :2 AgF₂ + Xe → 2 AgF + XeF₂ It also oxidises carbon monoxide to carbonyl fluoride. :2 AgF₂ + CO → 2 AgF + COF₂ It reacts with water to form oxygen gas: :4 AgF₂ + 4 H₂O → 2 Ag₂O + 8 HF + O₂ can be used to selectively fluorinate pyridine at the ortho position under mild conditions.

Safety

is a very strong oxidizer that reacts violently with water, reacts with dilute acids to produce ozone, oxidizes iodide to

iodine Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...

, and upon contact with

acetylene Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . 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 its pure ...

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 elemental silver.

References

External links

National Pollutant Inventory Fluoride and compounds fact sheet
{{DEFAULTSORT:Silver(Ii) Fluoride Fluorides Silver compounds Metal halides Fluorinating agents