In the gas phase, SbF5 adopts a trigonal bipyramidal structure of D3h
point group symmetry (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 [SbF4(μ-F)2]
n ((μ-F) denotes the fact that fluoride centres
bridge two Sb centers). The crystalline material is a tetramer, meaning that it has the formula [SbF4(μ-F)]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
monomeric 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. Antimony pentafluoride is a very strong oxidizing agent. Phosphorus burns on contact with it. SbF5 increases the oxidizing power of Fluorine, making it able to oxidize
oxygen: :2 SbF5 + F2 + 2 O2 → 2 Dioxygenyl|[O2]+[SbF6]− : SbF5 has also been used in the first discovered chemical reaction that produces
fluorine gas from fluoride compounds: : 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 [SbF6]−, called hexafluoroantimonate. It is the
conjugate base of the superacid
fluoroantimonic acid. [SbF6]− is a
weakly coordinating anion akin to
PF6−. Although it is only weakly basic, [SbF6]− does react with additional SbF5 to give a centrosymmetric
adduct: :SbF5 + [SbF6]− → [Sb2F11]− The [Sb2F11]− anion is one of the ions found in HF/SbF5 Mixture. ==Safety==