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Other names
3D model (JSmol)
  • InChI=1S/FHO2S/c1-4(2)3/h(H,2,3)/p-1
  • [O-]S(=O)F
Molar mass 83.06 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Fluorosulfite is an ion with the formula SO2F. The term is also used for compounds or salts containing this group. Fluorosulfite was discovered in 1953 by F Seel and H Meier.[1]

Organic compounds with the name "fluorosulfite" contain the group -OS(O)F.[2]


[((CH3)2N)3SO][SO2F] can be prepared from OSF4 and Me3SiNMe2.[3] Alkali metal fluorosulfites can be made by soaking the metal fluoride in liquid sulfur dioxide for a few days.[4] β-CsSO2F converts to α-CsSO2F when heated to 110 °C for a couple of days but remains stable below 50 °C.[4]


The fluorosulfite ion is tetrahedral, with sulfur at the top. The oxygen to sulfur bonds are 147.8 pm and the fluorine to sulfur bond is >169.0 pm long.[4] In solid ionic fluorosulfites, the ion is not fixed in orientation and continuously turns around resulting in dynamic disorder. At room temperature this turning rate is from 2×105 to 107 Hz. When cooled the rate of rotation slows, and can be frozen in place, resulting in static disorder.[4]

Fluorosulfite is isoelectronic with chloryl fluoride (ClO2F) and in compounds it resembles chlorate (ClO3).[4]

The heat of formation from fluoride (F) and sulfur dioxide (SO2) is 50 kcal mol−1.[5]


Fluorosulfites can react with chlorophosphazenes to make fluorophosphazenes:[6]

(NPCl2)n + 2n KSO2F (NPF2)n + 2n KCl + 2nSO2 n=3 or 4


Fluorosulfite is in the category of halosulfite ions which include chlorosulfite, bromosulfite and iodosulfite.[7] Related ions include cyanosulfite SO2CN.[8]


name formula weight system space group unit cell volume density properties ref
NO[SO2F] [1]
2-chloro-1,3-diisopropyl-4,5-dimethylimidazolium fluorosulfite C11H20FClN2O2S [9]
2-fluoro-1,3-diisopropyl-4,5-dimethylimidazolium fluorosulfite C11H20F2N2O2S P21/c a=15.097 b=13.406 c=15.776 β=113.54 Z=8 2927 [9]
(difluoromethyl)triphenylphosphonium fluorosulfite [Ph3PCF2H][SO2F] white, melt ~240 °C [10]
tetramethylammonium fluorosulfite [(CH3)4N][SO2F] 157.21 orthorhombic Pbca a=11.520 b=11.505 c=11.627 Z=8 1541.0 1.355 [3]
tris-dimethylamino sulfonium fluorosulfite [((CH3)2N)3S][SO2F] 247.35 orthorhombic Pnma a=14.690 b=11.174 c=7.3340 Z=4 1203.8 1.365 [3]
tris-dimethylamino sulfoxonium fluorosulfite [((CH3)2N)3SO][SO2F] 263.65 orthorhombic Pna21 a=21.850 b=6.733 c=8.194 Z=4 1205.5 1.451 [3]
potassium fluorosulfite KSO2F 122.16 monoclinic P21/m a=6.9725 b=5.6713 c=4.6653 β=107.702° Z=2 175.75 2.308 [4]
rubidium fluorosulfite RbSO2F monoclinic P21/m a=7.175 b=5.859 c=4.8416 β=107.18° Z=2 194.45 2.878 [4]
alpha caesium fluorosulfite α-CsSO2F orthorhombic Pnma a=7.9098 b=6.6607 c=7.9893 z=4 420.91 3.408 [4]
beta caesium fluorosulfite β-CsSO2F rhombohedral R3m a=6.5922 c=8.0050 z=3 301.27 3.571 [4]


  1. ^ a b Seel, F.; Meier, H. (December 1953). "Die Chemie des Nitrosyl-Ions. IX. Über den Chemismus des Bleikammerverfahrens". Zeitschrift für anorganische und allgemeine Chemie (in German). 274 (4–5): 197–222. doi:10.1002/zaac.19532740404. ISSN 0044-2313.
  2. ^ Baasner, Bernd (2014). Houben-Weyl Methods of Organic Chemistry Vol. E 10a, 4th Edition Supplement: Organo-Fluorine Compounds - Fluorinating Agents and Their Application in Organic Synthesis. Georg Thieme Verlag. pp. 332–334. ISBN 978-3-13-181544-6.
  3. ^ a b c d Lork, Enno; Mews, Rüdiger; Viets, Detlef; Watson, Paul G.; Borrmann, Tobias; Vij, Ashwani; Boatz, Jerry A.; Christe, Karl O. (March 2001). "Structure of the SO 2 F - Anion, a Problem Case 1". Inorganic Chemistry. 40 (6): 1303–1311. doi:10.1021/ic000616p. ISSN 0020-1669. PMID 11300833.
  4. ^ a b c d e f g h i Kessler, Ulrich; van Wüllen, Leo; Jansen, Martin (2001-12-01). "Structure of the Fluorosulfite Anion: Rotational Disorder of SO2F in the Alkali Metal Fluorosulfites and Crystal Structures of α- and β-CsSO2F". Inorganic Chemistry. 40 (27): 7040–7046. doi:10.1021/ic010303+. ISSN 0020-1669. PMID 11754288.
  5. ^ Maulitz, Andreas H.; Boese, Roland; Kuhn, Norbert (April 1995). "Ab initio studies on halosulfite ions". Journal of Molecular Structure: THEOCHEM. 333 (3): 227–232. doi:10.1016/0166-1280(94)03955-K.
  6. ^ Allcock, H. (2012). Phosphorus-Nitrogen Compounds: Cyclic, Linear, and High Polymeric Systems. Elsevier. p. 207. ISBN 978-0-323-14751-4.
  7. ^ Robertson, Katherine N.; Land, Michael A.; Murphy, Luke J.; Doyle, Kirstin A.; Clyburne, Jason A. C. (2018-07-20). "Sulfur dioxide–halide ion complexes: a crystallographic investigation of bonding". Acta Crystallographica Section A. 74 (a1): a341. doi:10.1107/S0108767318096599. ISSN 2053-2733.
  8. ^ Kornath, Andreas; Blecher, Oliver; Ludwig, Ralf (April 1999). "Synthesis and Characterization of Tetramethylammonium Cyanosulfite, (CH3)4N+SO2CN". Journal of the American Chemical Society. 121 (16): 4019–4022. doi:10.1021/ja9833422. ISSN 0002-7863.
  9. ^ a b Kuhn, Norbert; Bohnen, Hans; Fahl, Joanna; Bläser, Dieter; Boese, Roland (December 1996). "Derivate des Imidazols, XIX. Koordination oder Reduktion? Zur Reaktion von 1,3-Diisopropyl-4,5-dimethylimidazol-2-yliden mit Schwefelhalogeniden und Schwefeloxidhalogeniden". Chemische Berichte (in German). 129 (12): 1579–1586. doi:10.1002/cber.19961291228.
  10. ^ Zhu, Shi-Zheng; Huang, Qi-Chen; Wu, Kuang (September 1994). "Synthesis and Structure of (Difluoromethyl)triphenylphosphonium Fluorosulfite, Evidence for Formation of Difluorosulfene as an Intermediate". Inorganic Chemistry. 33 (20): 4584–4585. doi:10.1021/ic00098a028. ISSN 0020-1669.