Fluorosulfates
The fluorosulfates or fluorosulfonates are a set of salts of fluorosulfuric acid with an ion formula SO3F−. The flurosulfate anion can be teated as though it were a hydrogen sulfate anion with hydroxyl substituted by fluorine. The fluorosulfate ion has a low propensity to form complexes with the metal cation. Since fluorine is similar in size to oxygen, the fluorosulfate ion is roughly tetrahedral and forms salts similar to those of perchlorate. It is isoelectronic with hydrogen sulfate, HSO4−. When an organic group is substituted for the anions, organic fluorosulfonates are formed.
In solution the fluorosulfate anion is completely ionised. The volume is 47.8 cm3/mol. Nearly every metal ion and quaternary ammonium ions can form a salt with flourosulfate. Different ways to make these salts include treating a metal chloride with anhydrous fluorosulfuric acid, which releases hydrogen chloride gas. Double decomposition methods with a metal sulfate with barium fluorosulfate, or a metal chloride with silver fluorosulfate, leave the metal salt in solution.
The fluorosulfate anion is weakly coordinating, and is difficult to oxidise. It is important historically as a model weakly coordinating anion. But in the twenty-first century fluorosulfate was superseded in this use, in particular by BARF.
Many pseudobinary fluorosulfate salts are known. They are called pseudobinary, because although there is one other element, there are four kinds of atoms. Non-metal pseudobinary fluorosulfates are known including those of halogens and xenon.
Some psudoternary fluorosulfates exist including Cs[Sb(SO3F)6], Cs[Au(SO3F)4], Cs2[Pt(SO3F)6]
Related ionic compounds are the fluoroselenites SeO3F− and the fluorosulfites SO2F−.
...
Wikipedia