Antimony pentafluoride is the

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

with the formula Sb F₅. This colourless, viscous liquid is a valuable

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...

and a component of the superacid

fluoroantimonic acid Fluoroantimonic acid is a mixture of hydrogen fluoride and antimony pentafluoride, containing various cations and anions (the simplest being and ). This substance is a superacid that can be over a billion times stronger than 100% pure sulfuri ...

, formed when mixing liquid HF with liquid SbF₅ in a 2:1 ratio. It is notable for its

ity and its ability to react with almost all known compounds.

Preparation

Antimony pentafluoride is prepared by the reaction of

antimony pentachloride Antimony pentachloride is a chemical compound with the formula SbCl5. It is a colourless oil, but typical samples are yellowish due to dissolved chlorine. Owing to its tendency to hydrolyse to hydrochloric acid, SbCl5 is a highly corrosive substa ...

with anhydrous

hydrogen fluoride Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock i ...

:Sabina C. Grund, Kunibert Hanusch, Hans J. Breunig, Hans Uwe Wolf "Antimony and Antimony Compounds" in Ullmann's Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. :SbCl₅ + 5 HF → SbF₅ + 5 HCl It can also be prepared from antimony trifluoride and fluorine.

Structure and chemical reactions

In the gas phase, SbF₅ adopts a trigonal bipyramidal structure of D_3h

point group symmetry In group theory, the symmetry group of a geometric object is the group of all transformations under which the object is invariant, endowed with the group operation of composition. Such a transformation is an invertible mapping of the ambient ...

(see picture). The material adopts a more complicated structure in the liquid and solid states. The liquid contains polymers wherein each Sb is octahedral, the structure being described with the formula bF₄(μ-F)₂sub>''n'' ((μ-F) denotes the fact that fluoride centres

bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...

two Sb centres). The crystalline material is a tetramer, meaning that it has the formula bF₄(μ-F)sub>4. The Sb-F bonds are 2.02 Å within the eight-membered Sb₄F₄ ring; the remaining fluoride ligands radiating from the four Sb centers are shorter at 1.82 Å. The related species PF₅ and AsF₅ are

monomer In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification Mo ...

ic in the solid and liquid states, probably due to the smaller sizes of the central atom, which limits their coordination number. BiF₅ is a polymer. In the same way that SbF₅ enhances the Brønsted acidity of HF, it augments the

oxidizing Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

power of F₂. This effect is illustrated by the oxidation of

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

:Shamir, J.; Binenboym, J. "Dioxygenyl Salts" ''Inorganic Syntheses'' 1973, XIV, 109-122. :2 SbF₅ + F₂ + 2 O₂ → 2 ₂sup>+ bF₆sup>− Antimony pentafluoride has also been used in the first discovered chemical reaction that produces

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 ...

gas from fluoride compounds: :4 + 2 → 4 + 2 + The driving force for this reaction is the high affinity of SbF₅ for , which is the same property that recommends the use of SbF₅ to generate superacids.

Hexafluoroantimonate

SbF₅ is a strong Lewis acid, exceptionally so toward sources of F⁻ to give the very stable anion bF₆sup>−, called hexafluoroantimonate. bF₆sup>− is a

weakly coordinating anion Anions that interact weakly with cations are termed non-coordinating anions, although a more accurate term is weakly coordinating anion. Non-coordinating anions are useful in studying the reactivity of electrophilic cations. They are commonly found ...

akin to PF₆⁻. Although it is only weakly basic, bF₆sup>− does react with additional SbF₅ to give a centrosymmetric

adduct An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...

: :SbF₅ + bF₆sup>− → b₂F₁₁sup>−

Safety

SbF₅ reacts violently with many compounds, often releasing dangerous

. It is corrosive to the skin and eyes.

References

External links

WebBook page for SbF5National Pollutant Inventory - Antimony and compounds fact sheetNational Pollutant Inventory - Fluoride compounds fact sheet
{{DEFAULTSORT:Antimony Pentafluoride Superacids Antimony(V) compounds Fluorides Metal halides