# Fluorosulfates

The fluorosulfates or fluorosulfonates are a set of salts of fluorosulfuric acid with an ion formula SO$_3$F$^−$. The fluorosulfate anion can be treated as though it were a hydrogen sulfate anion with hydroxyl substituted by fluorine. The fluorosulfate ion has a low propensity to form complexes with metal cations. Since fluorine is similar in size to oxygen, the fluorosulfate ion is roughly tetrahedral and forms salts similar to those of the perchlorate ion. It is isoelectronic with sulfate, SO$_4$$^{−2}$. When an organic group is substituted for the anions, organic fluorosulfonates are formed.
In solution the fluorosulfate anion is completely ionised. The volume of the ions is 47.8 cm$^3$/mol. Most metal ions, and quaternary ammonium ions, can form fluorosulfate salts. Different ways to make these salts include treating a metal chloride with anhydrous fluorosulfuric acid, which releases hydrogen chloride gas. Double decomposition methods utilising a metal sulfate with barium fluorosulfate, or a metal chloride with silver fluorosulfate, leave the metal salt in solution.
The fluorosulfate anion is weakly coordinating, and is difficult to oxidise. It is important historically as a model weakly coordinating anion. However, by the twenty-first century fluorosulfate was superseded in this use, in particular by BARF.
Many pseudobinary fluorosulfate salts are known. They are called pseudobinary, because although there is one other element, there are four kinds of atoms. Nonmetal pseudobinary fluorosulfates are known including those of halogens and xenon.
Some pseudoternary fluorosulfates exist including Cs[Sb(SO$_3$F)$_6$], Cs[Au(SO$_3$F)$_4$], Cs$_2$[Pt(SO$_3$F)$_6$]
Related ionic compounds are the fluoroselenites SeO$_3$F$^−$ and the fluorosulfites SO$_2$F$^−$. The sulfate fluorides are distinct, as they contain fluoride ions without a bond to the sulfate groups.
One fluorosulfate containing mineral called reederite-(Y) exists. It is a mixed anion compound that also contains carbonate and chloride.

## Compounds

| Formula | Name | Colour | Decomposition temperature (°C) | Decomposition product | Crystal |
| LiSO$_3$F | lithium fluorosulfate | | | | C2/m a=8.54 b=7.62 c=4.98 β=90.0 V=81 |
| Be(SO$_3$F)$_2$ | | | | SO$_3$ | |
| CF$_3$(SO$_3$F) | | | | | |
| CF$_2$(SO$_3$F)$_2$ | | | | | |
| CF(SO$_3$F)$_3$ | | | | | |
| C(SO$_3$F)$_4$ | | | | | |
| NH$_4$SO$_3$F | ammonium fluorosulfate | | | | Orthorhombic Pnma a=8.97 b=6.00 c=7.54 V=101.4 Z=4 |
| N(CH$_3$)$_4$SO$_3$F | tetramethylammonium fluorosulfate | | | | Orthorhombic Pnma a=8.38 b=8.38 c=5.86 V=102.88 Z=4 |
| N$^{III}$OSO$_3$F | nitrosyl fluorosulfonate | | melts 156 | | density 1.96 |
| N$^V$O$_2$SO$_3$F | nitronium fluorosulfinate | | | | |
| S$_4$(SO$_3$F)$_2$ | tetrasulfur fluorosulfate | | | | |
| S$_2$O$_6$F$_2$ | bis(fluorosulfuryl) peroxide | | | | |
| NaSO$_3$F | sodium fluorosulfate | | | | Hexagonal a=5.4812 b=5.4812 c=6.5172 V=169.57 Z=2 D=2.390 |
| Mg(SO$_3$F)$_2$ | magnesium fluorosulfonate | | | SO$_3$ | |
| Al(SO$_3$F)$_2$.3CH$_3$CN | | | | | |
| Al(SO$_3$F)$_3$ | aluminium fluorosulfate | white | | | polymeric, fluorosulfate is bidentate and bridged |
| Si(SO$_3$F)$_4$ | silicon tetrafluorosulfonate | | | S$_2$O$_5$F$_2$ SiO$_2$ | |
| P$^V$O(SO$_3$F)$_3$ | phosphoryl trifluorosulfonate | | | S$_2$O$_5$F$_2$ | |
| PO(SO$_3$F) | | | | | |
| ClSO$_3$F | chlorosulfuryl fluoride | | | | |
| ClO$_2$SO$_3$F | chloryl fluorosulfate | red or pale yellow | low melting point | | |
| KSO$_3$F | potassium fluorosulfate | | | | Pnma a=8.62 b=5.84 c=7.35 V=92.5 |
| Ca(SO$_3$F)$_2$ | | | | CaF$_2$ SO$_3$ | |
| Ti$^{IV}$(SO$_3$F)$_4$ | titanium tetrafluorosulfonate titanium(IV) fluorosulfonate | | | S$_2$O$_5$F$_2$ | |
| VO(SO$_3$F)$_3$ | | deep red liquid | | | |
| Cr$^{VI}$O$_2$(SO$_3$F)$_2$ | chromyl fluorosulfate | green or brown | | | |
| Mn(SO$_3$F)$_2$ | | | | | |
| MnO(SO$_3$F) | | brownish black | | | |
| Mn(SO$_3$F)$_3$ | | | | | |
| Mn$^I$(CO)$_4$(SO$_3$F) | | | | | |
| Mn$^I$(CO)$_5$(SO$_3$F) | | | | | |
| Rb$_2$Mn(SO$_3$F)$_5$ | | | | | |
| Cs$_2$Mn(SO$_3$F)$_5$ | | | | | |
| Fe$^{III}$(SO$_3$F)$_3$ | ferric fluorosulfate | green grey | 230 | S$_2$O$_5$F$_2$ SO$_3$ FeF$_3$ | |
| CoO(SO$_3$F) | | chocolate brown | | | |
| Ni(SO$_3$F)$_2$ | | | | | |
| Ni(py)$_4$(SO$_3$F)$_2$ py=pyridine | | | | | |
| NiO(SO$_3$F) | | dark grey | | | |
| Cu$^{II}$(SO$_3$F)$_2$ | cupric fluorosulfate copper(II) fluorosulfate | pale yellow/white | 210 | S$_2$O$_5$F$_2$ SO$_3$ CuSO$_4$ CuF$_2$ | |
| Cu$^{II}$(py)$_4$(SO$_3$F)$_2$ py=pyridine | | | | | |
| Cu(SO$_3$F).CH$_3$CN | | | | | |
| Zn(SO$_3$F)$_2$ | zinc fluorosulfate | white | 280 | SO$_3$ ZnF$_2$ | |
| Zn(py)$_4$(SO$_3$F)$_2$ py=pyridine | | | | | |
| Ga$^{III}$(SO$_3$F)$_3$ | gallium fluorosulfate | white | 240 | SO$_3$ | polymeric |
| As$^{III}$(SO$_3$F)$_3$ | arsenic trifluorosulfonate arsenic(III) fluorosulfonate | | | S$_2$O$_5$F$_2$ | |
| As$^V$F$_2$(SO$_3$F)$_3$ | | | | | |
| As$^V$F$_3$(SO$_3$F)$_2$ | | | | | |
| BrSO$_3$F | bromosulfuryl fluoride | red liquid | | | |
| RbSO$_3$F | rubidium fluorosulfate | | | | Orthorhombic Pnma a=8.7812 b=6.0318 c=7.5108 V=397.82 Z=4 D=3.081 |
| Sr(SO$_3$F)$_2$ | | | | SO$_2$F$_2$ | |
| MoO$_2$(SO$_3$F)$_2$ | | | | | |
| Nb$^V$(SO$_3$F)$_5$ | niobium pentafluorosulfonate niobium(V) fluorosulfate | colourless solution | 25 | SO$_3$ | |
| NbO(SO$_3$F)$_3$ | | yellow liquid | | | |
| Ru(SO$_3$F)$_3$ | | very dark red | | | |
| CsRu(SO$_3$F)$_4$ | | dark brown | | | |
| ClO$_2$Ru(SO$_3$F)$_4$ | | black | | | |
| CsRu(SO$_3$F)$_5$ | | red brown | | | |
| Cs$_2$Ru(SO$_3$F)$_6$ | | bright orange | | | |
| K$_2$Ru(SO$_3$F)$_6$ | | bright orange | | | |
| Rh(SO$_3$F)$_3$ | | bright orange | 190 | | |
| Pd(SO$_3$F)$_2$ | | purple | 250 | SO$_3$ PdF$_2$ | |
| Pd(SO$_3$F)$_3$ | | dark brown | 180 | | |
| Pd(CO)$_2$(SO$_3$F)$_2$ | bis(carbonyl)palladium(II) fluorosulfate | yellow | | | |
| c-Pd$_2$(μ-CO)$_2$](SO$_3$F)$_2$ | cyclo-Bis(μ-carbonyl)dipalladium(I) Fluorosulfate | orange | | | monoclinic C2/c a=11.495 b=8.255 c=9.556 β =91.94 Z=8 |
| Ag$^I$SO$_3$F | silver fluorosulfate | | | | P2$_1$/m a=5.413 b=8.174 c=7.544 β=94.60 V=83.17 Z=4 |
| Ag$^{II}$(SO$_3$F)$_2$ | silver(II) fluorosulfate | dark brown | room temperature fast >120 | Ag$_3$(SO$_3$F)$_4$ SO$_3$F$^•$ | monoclinic a=10.5130 Å, b= 7.7524 Å, c = 8.9366 Å, β = 117.867° V =643.88 Å$^3$, Z = 4, d = 3.15 gcm$^{−3}$ |
| Ag$_2$O(SO$_3$F)$_2$ | black | | | | |
| Ag$^I$$_2$Ag$^{II}$(SO$_3$F)$_4$ | silver(I, II) fluorosulfate | black | | | |
| KAg$^I$$_2$Ag$^{II}$(SO$_3$F)$_5$ | | | | | orthorhombic P 222$_1$, a = 6.4736 b = 7.3915 c = 17.7736 |
| RbAg$^I$$_2$Ag$^{II}$(SO$_3$F)$_5$ | | | | | orthorhombic P 222$_1$, a = 6.4828 b = 7.3551c = 18.0262 |
| RbAg$^{II}$(SO$_3$F)$_3$ | | | | | monoclinic P 2$_1$/m , a = 15.815 b = 15.486 c = 17.021 β = 101.513 |
| CsAg$^{II}$(SO$_3$F)$_3$ | | | | | triclinic P1_ , a = 14.9241 b = 9.7046 c = 17.8465 α = 109.116°, β = 84.655° γ = 119.171° |
| Cd(SO$_3$F)$_2$ | | | | | |
| In$^{III}$(SO$_3$F)$_3$ | Indium tri(fluorosulfate) | | | | polymeric |
| Sn$^{IV}$(SO$_3$F)$_4$ | tin tetrafluorosulfonate tin(IV) fluorosulfonate | | | S$_2$O$_5$F$_2$ | |
| SbF$_4$SO$_3$F | | | | | |
| Sb(SO$_3$F)$_2$.2CH$_3$CN | | | | | |
| Cs[Sb(SO$_3$F)$_6$] | Cesium hexakis(fluorosulfato)antimonate(V) | | | | trigonal, R3̄ a = 12.0317 Å, c = 12.026 Å, Z = 3 |
| TeF$_5$SO$_3$F | | | | | |
| ISO$_3$F | | | | | |
| ICl$_2$SO$_3$F | | | | | |
| IBr$_2$SO$_3$F | | rust brown | 90 | ISO$_3$F, Br$_2$ | |
| IO$_2$SO$_3$F | iodyl fluorosulfate | | 100 | | yellow |
| I$^V$F$_3$(SO$_3$F)$_2$ | iodine trifluoride bisfluorosulfonate | | | | |
| FXe(SO$_3$F) | | | | | |
| Xe$^{II}$(SO$_3$F)$_2$ | xenon(II) fluorosulfate | | | | |
| F$_5$Xe$^{VI}$(SO$_3$F) | | | | | |
| CsSO$_3$F | caesium fluorosulfate | | | | l4$_1$/a a=5.611 b=5.611 c=14.13 V=111.3 Z=4 |
| Cs[H(SO$_3$F)$_2$] | | | | | |
| Ba(SO$_3$F)$_2$ | | | | BaSO$_4$ SO$_2$F$_2$ | |
| Ho(SO$_3$F)$_3$ | holmium fluorosulfate | | | | |
| Ta$^V$(SO$_3$F)$_5$ | tantalum pentafluorosulfonate pentakis(fluorosulfonato)tantalum(V) | colourless solution | | | |
| Ta$^V$O(SO$_3$F)$_3$ | | yellow liquid | | | |
| W$^{VI}$O(SO$_3$F)$_4$ | oxo tetrakis(fluorosulfato)tungsten(VI) | colourless liquid | | | |
| Re$^{VII}$O$_2$(SO$_3$F)$_3$ | dioxo trisfluorosulfato rhenium(VII) | white solid | | | |
| Re$^{VII}$O$_3$(SO$_3$F) | trioxo fluorosulfato rhenium(VII) | yellow liquid | | | |
| Re$^I$(CO)$_5$(SO$_3$F) | | | | | |
| Os(SO$_3$F)$_3$ | | bright green | 130 | | |
| Ir(SO$_3$F)$_3$ | | | | | |
| Ir(SO$_3$F)$_4$ | | | | | |
| Cs$_2$Ir(SO$_3$F)$_6$ | | | | | |
| BaIr(SO$_3$F)$_6$ | | | | | |
| (ClO$_2$)$_2$Ir(SO$_3$F)$_6$ | | | | | |
| mer-Ir(CO)$_3$(SO$_3$F)$_3$ | mer-Tris(carbonyl)iridium(III) Fluorosulfate | colourless | | | Monoclinic P2$_1$/c, Z = 4, a = 8.476 b = 12.868 c = 12.588 β = 108.24°, V = 1304.0 MW 573.42 |
| Pt(SO$_3$F)$_4$ | | | | | |
| Cs$_2$[Pt(SO$_3$F)$_6$] | cesium hexakis(fluorosulfato)platinate(IV) | | | | |
| Pt(CO)$_2$(SO$_3$F)$_2$ | bis(carbonyl)platinum(II) fluorosulfate | creamy white | | | |
| Au$^I$CO(SO$_3$F) | | | | | |
| Au$^{II}$(SO$_3$F)$_2$ | gold(II) fluorosulfate | yellow red | | | |
| Au$^{III}$(SO$_3$F)$_3$ | | | | | |
| Cs[Au(SO$_3$F)$_4$] | Cesium Tetrakis(fluorosulfato)aurate(III) | | | | monoclinic, C2/c a = 17.725 Å, b = 5.822 Å, c = 14.624 Å, β = 102.120°, Z = 4 |
| Hg(SO$_3$F)$_2$ | mercuric fluorosulfate | | | | density 3.715 |
| TlSO$_3$F | thallium fluorosulfate | | | | Orthorhombic a=5.2205 b=5.5141 c=13.4378 V=386.83 Z=4 D=5.210 |
| TlO(SO$_3$F) | | brown | | | |
| Tl$^{III}$(SO$_3$F)$_3$ | thallium tri(fluorosulfate) thallium(III) fluorosulfonate | | | | |
| Pb$^{IV}$(SO$_3$F)$_4$ | lead(IV) fluorosulfate | | | | |
| Bi$^{III}$(SO$_3$F)$_3$ | bismuth(III) fluorosulfate tris(fluorosulfonato)bismuth(III) | | | | |
| Th$^{IV}$(SO$_3$F)$_4$ | thorium(IV) fluorosulfate | | | | |
| U$^{II}$(SO$_3$F)$_2$ | | | | | yellow |
| U$^{III}$(SO$_3$F)$_3$ | | | | | green |
| U$^{IV}$(SO$_3$F)$_4$ | uranium(IV) fluorosulfate | | | | tan |
| Na$_2$U$^{IV}$(SO$_3$F)$_6$ | | | | | |
| U$^{IV}$O(SO$_3$F)$_2$ | oxouranium(IV) fluorosulfate | | | | |
| U$^{VI}$O$_2$(SO$_3$F)$_2$ | uranyl fluorosulfate dioxouranium(VI) fluorosulfate | | | | |