en Sulfur tetrafluoride

Sulfur tetrafluoride
	Structural formula of sulfur tetrafluoride, showing dimernsions
Ball-and-stick model of sulfur tetrafluoride	Space-filling model of sulfur tetrafluoride
Names
	IUPAC name Sulfur(IV) fluoride
	Other names Sulfur tetrafluoride
Identifiers
CAS Number	7783-60-0 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:30495 ;
ChemSpider	22961 ;
ECHA InfoCard	100.029.103
PubChem CID	24555;
RTECS number	WT4800000;
UNII	F4P8J39GOF ;
UN number	2418
CompTox Dashboard (EPA)	DTXSID40893074 ;
	InChI InChI=1S/F4S/c1-5(2,3)4 Key: QHMQWEPBXSHHLH-UHFFFAOYSA-N ; InChI=1/F4S/c1-5(2,3)4 Key: QHMQWEPBXSHHLH-UHFFFAOYAT;
	SMILES FS(F)(F)F;
Properties
Chemical formula	SF4
Molar mass	108.07 g/mol
Appearance	colorless gas
Density	1.95 g/cm3, −78 °C
Melting point	−121.0 °C
Boiling point	−38 °C
Solubility in water	reacts
Vapor pressure	10.5 atm (22 °C)
Structure
Molecular shape	Seesaw (C2v)
Dipole moment	0.632 D
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	highly reactive and toxic gas
NFPA 704 (fire diamond)	3 0 2 W
	NIOSH (US health exposure limits):
PEL (Permissible)	none
REL (Recommended)	C 0.1 ppm (0.4 mg/m3)
IDLH (Immediate danger)	N.D.
Safety data sheet (SDS)	ICSC 1456
Related compounds
Other anions	Sulfur dichloride; Disulfur dibromide; Sulfur trifluoride
Other cations	Oxygen difluoride; Selenium tetrafluoride; Tellurium tetrafluoride
Related sulfur fluorides	Disulfur difluoride; Sulfur difluoride; Disulfur decafluoride; Sulfur hexafluoride
Related compounds	Thionyl fluoride
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Sulfur tetrafluoride is a chemical compound with the formula S F₄. It is a colorless corrosive gas that releases dangerous hydrogen fluoride gas upon exposure to water or moisture. Sulfur tetrafluoride is a useful reagent for the preparation of organofluorine compounds,^[3] some of which are important in the pharmaceutical and specialty chemical industries.

Structure

Sulfur in SF₄ is in the +4 oxidation state, with one lone pair of electrons. The atoms in SF₄ are arranged in a see-saw shape, with the sulfur atom at the center. One of the three equatorial positions is occupied by a nonbonding lone pair of electrons. Consequently, the molecule has two distinct types of F ligands, two axial and two equatorial. The relevant bond distances are S–F_ax = 164.3 pm and S–F_eq = 154.2 pm. It is typical for the axial ligands in hypervalent molecules to be bonded less strongly.

The ¹⁹F NMR spectrum of SF₄ reveals only one signal, which indicates that the axial and equatorial F atom positions rapidly interconvert via pseudorotation.^[4]

Intramolecular dynamic equilibration of SF₄.

Synthesis and manufacture

At the laboratory scale, sulfur tetrafluoride is prepared from elemental sulfur and cobaltic fluoride^[5]

S + 4CoF₃ → SF₄ + 4CoF₂

SF₄ is industrially produced by the reaction of SCl₂ and NaF with acetonitrile as a catalyst^[6]

3 SCl₂ + 4 NaF → SF₄ + S₂Cl₂ + 4 NaCl

At higher temperatures (e.g. 225–450 °C), the solvent is superfluous. Moreover, sulfur dichloride may be replaced by elemental sulfur (S) and chlorine (Cl₂).^[7]^[8]

A low-temperature (e.g. 20–86 °C) alternative to the chlorinative process above uses liquid bromine (Br₂) as oxidant and solvent:^[9]

S(s) + 2 Br₂(l; excess) + 4KF(s) → SF₄↑ + 4 KBr(brom)

Use in synthesis of organofluorine compounds

In organic synthesis, SF₄ is used to convert COH and C=O groups into CF and CF₂ groups, respectively.^[10] The efficiency of these conversions are highly variable.

In the laboratory, the use of SF₄ has been superseded by the safer and more easily handled diethylaminosulfur trifluoride, (C₂H₅)₂NSF₃, "DAST":^[11] This reagent is prepared from SF₄:^[12]

SF₄ + (CH₃)₃SiN(C₂H₅)₂ → (C₂H₅)₂NSF₃ + (CH₃)₃SiF

Other reactions

Sulfur chloride pentafluoride (SF
₅Cl), a useful source of the SF₅ group, is prepared from SF₄.^[13]

SF₄ + Cl₂ + CsF → SF₅Cl + CsCl

Hydrolysis of SF₄ gives sulfur dioxide:^[14]

SF₄ + 2 H₂O → SO₂ + 4 HF

This reaction proceeds via the intermediacy of thionyl fluoride, which usually does not interfere with the use of SF₄ as a reagent.^[6]

When amines are treated with SF₄ and a base, aminosulfur difluorides result.^[15]

Toxicity

SF
₄ reacts inside the lungs with moisture, forming sulfur dioxide and hydrogen fluoride which forms highly toxic and corrosive hydrofluoric acid ^[16]

References

^ ^a ^b ^c ^d NIOSH Pocket Guide to Chemical Hazards. "#0580". National Institute for Occupational Safety and Health (NIOSH).
^ Tolles, W. M.; W. M. Gwinn, W. D. (1962). "Structure and Dipole Moment for SF₄". J. Chem. Phys. 36 (5): 1119–1121. Bibcode:1962JChPh..36.1119T. doi:10.1063/1.1732702.
^ Wang, C.-L. J. (2004). "Sulfur Tetrafluoride". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X. hdl:10261/236866. ISBN 9780471936237.
^ Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.
^ Kwasnik, W. (1963). "Fluorine compounds: Sulfur tetrafluoride". In Brauer, Georg (ed.). Handbook of Preparative Inorganic Chemistry. Vol. 1. Translated by Riley, Reed F. (2nd ed.). NY, NY: Academic Press. p. 168. LCCN 63-14307 – via the Internet Archive.
^ ^a ^b Fawcett, F. S.; Tullock, C. W. (1963). "Sulfur(IV) Fluoride" (PDF). Inorganic Syntheses. Vol. 7. pp. 119–124. doi:10.1002/9780470132388.ch33. ISBN 978-0-470-13166-4.
^ Tullock, C. W.; Fawcett, F. S.; Smith, W. C.; Coffman, D. D. (1960). "The Chemistry of Sulfur Tetrafluoride. I. The Synthesis of Sulfur Tetrafluoride". J. Am. Chem. Soc. 82 (3): 539–542. doi:10.1021/ja01488a011.
^ US 2992073, Tullock, C.W., "Synthesis of Sulfur Tetrafluoride", issued 1961
^ Winter, R.W.; Cook P.W. (2010). "A simplified and efficient bromine-facilitated SF₄-preparation method". J. Fluorine Chem. 131: 780-783. doi:10.1016/j.jfluchem.2010.03.016
^ Hasek, W. R. (1961). "1,1,1-Trifluoroheptane". Organic Syntheses. 41: 104. doi:10.15227/orgsyn.041.0104.
^ Fauq, A. H. (2004). "N,N-Diethylaminosulfur Trifluoride". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X. hdl:10261/236866. ISBN 9780471936237..
^ W. J. Middleton; E. M. Bingham (1977). "Diethylaminosulfur Trifluoride". Organic Syntheses. 57: 440. doi:10.15227/orgsyn.057.0050.
^ Nyman, F.; Roberts, H. L.; Seaton, T. (1966). "Sulfur Chloride Pentafluoride" (PDF). Inorganic Syntheses. Vol. 8. McGraw-Hill. p. 160. doi:10.1002/9780470132395.ch42. ISBN 9780470132395.
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
^ Grunwell, John R.; Dye, Sandra L. (1975). "Novel generation of benzonitrile-N-sulfide". Tetrahedron Letters. 16 (21): 1739–1740. doi:10.1016/s0040-4039(00)72247-7. ISSN 0040-4039.
^ Johnston, H. (2003). A Bridge not Attacked: Chemical Warfare Civilian Research During World War II. World Scientific. pp. 33–36. ISBN 981-238-153-8.

[PGCH-1] NIOSH Pocket Guide to Chemical Hazards. "#0580". National Institute for Occupational Safety and Health (NIOSH).

[2] Tolles, W. M.; W. M. Gwinn, W. D. (1962). "Structure and Dipole Moment for SF₄". J. Chem. Phys. 36 (5): 1119–1121. Bibcode:1962JChPh..36.1119T. doi:10.1063/1.1732702.

[3] Wang, C.-L. J. (2004). "Sulfur Tetrafluoride". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X. hdl:10261/236866. ISBN 9780471936237.

[4] Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.

[5] Kwasnik, W. (1963). "Fluorine compounds: Sulfur tetrafluoride". In Brauer, Georg (ed.). Handbook of Preparative Inorganic Chemistry. Vol. 1. Translated by Riley, Reed F. (2nd ed.). NY, NY: Academic Press. p. 168. LCCN 63-14307 – via the Internet Archive.

[IS-6] Fawcett, F. S.; Tullock, C. W. (1963). "Sulfur(IV) Fluoride" (PDF). Inorganic Syntheses. Vol. 7. pp. 119–124. doi:10.1002/9780470132388.ch33. ISBN 978-0-470-13166-4.

[IN-7] Tullock, C. W.; Fawcett, F. S.; Smith, W. C.; Coffman, D. D. (1960). "The Chemistry of Sulfur Tetrafluoride. I. The Synthesis of Sulfur Tetrafluoride". J. Am. Chem. Soc. 82 (3): 539–542. doi:10.1021/ja01488a011.

[TP-8] US 2992073, Tullock, C.W., "Synthesis of Sulfur Tetrafluoride", issued 1961

[9] Winter, R.W.; Cook P.W. (2010). "A simplified and efficient bromine-facilitated SF₄-preparation method". J. Fluorine Chem. 131: 780-783. doi:10.1016/j.jfluchem.2010.03.016

[10] Hasek, W. R. (1961). "1,1,1-Trifluoroheptane". Organic Syntheses. 41: 104. doi:10.15227/orgsyn.041.0104.

[11] Fauq, A. H. (2004). "N,N-Diethylaminosulfur Trifluoride". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X. hdl:10261/236866. ISBN 9780471936237..

[12] W. J. Middleton; E. M. Bingham (1977). "Diethylaminosulfur Trifluoride". Organic Syntheses. 57: 440. doi:10.15227/orgsyn.057.0050.

[Nyman-13] Nyman, F.; Roberts, H. L.; Seaton, T. (1966). "Sulfur Chloride Pentafluoride" (PDF). Inorganic Syntheses. Vol. 8. McGraw-Hill. p. 160. doi:10.1002/9780470132395.ch42. ISBN 9780470132395.

[14] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[15] Grunwell, John R.; Dye, Sandra L. (1975). "Novel generation of benzonitrile-N-sulfide". Tetrahedron Letters. 16 (21): 1739–1740. doi:10.1016/s0040-4039(00)72247-7. ISSN 0040-4039.

[16] Johnston, H. (2003). A Bridge not Attacked: Chemical Warfare Civilian Research During World War II. World Scientific. pp. 33–36. ISBN 981-238-153-8.

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