Sulfur tetrafluoride
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Names | |||
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IUPAC name Sulfur(IV) fluoride | |||
Other names Sulfur tetrafluoride | |||
Identifiers | |||
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3D model (JSmol) |
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ChEBI |
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ChemSpider |
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ECHA InfoCard | 100.029.103 | ||
PubChem CID |
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RTECS number |
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UNII |
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UN number | 2418 | ||
CompTox Dashboard (EPA) |
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InChI
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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)[1] | ||
Structure | |||
Seesaw (C2v) | |||
0.632 D[2] | |||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards | highly toxic corrosive | ||
NFPA 704 (fire diamond) | 3 0 2 W | ||
NIOSH (US health exposure limits): | |||
PEL (Permissible) | none[1] | ||
REL (Recommended) | C 0.1 ppm (0.4 mg/m3)[1] | ||
IDLH (Immediate danger) | N.D.[1] | ||
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). Y verify (what is YN ?) Infobox references |
Sulfur tetrafluoride is the chemical compound with the formula SF4. It is a colorless corrosive gas that releases dangerous HF upon exposure to water or moisture. Despite these unwelcome characteristics, this compound 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 formal +4 oxidation state. Of sulfur's total of six valence electrons, two form a lone pair. The structure of SF4 can therefore be anticipated using the principles of VSEPR theory: it is a see-saw shape, with S 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–Fax = 164.3 pm and S–Feq = 154.2 pm. It is typical for the axial ligands in hypervalent molecules to be bonded less strongly. In contrast to SF4, the related molecule SF6 has sulfur in the 6+ state, no valence electrons remain nonbonding on sulfur, hence the molecule adopts a highly symmetrical octahedral structure. Further contrasting with SF4, SF6 is extraordinarily inert chemically.
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]
Synthesis and manufacture
At the laboratory scale, fluorination of elemental sulfur with cobaltic fluoride suffices:[5]
- S + 4CoF3 → SF4 + 4CoF2
For larger-scale syntheses, SF4 is produced by the reaction of SCl2 and NaF in acetonitrile:[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)
For the 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 more conveniently handled diethylaminosulfur trifluoride, Et2NSF3, "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, iminosulfur difluorides result.[15]
Toxicity
SF
4 reacts inside the lungs with moisture, generating sulfur dioxide and hydrogen fluoride:[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.
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HF | He | |||||||||||||||||
LiF | BeF2 | BF BF3 B2F4 | CF4 CxFy | NF3 N2F4 | OF OF2 O2F2 O2F | F− | Ne | |||||||||||
NaF | MgF2 | AlF AlF3 | SiF4 | P2F4 PF3 PF5 | S2F2 SF2 S2F4 SF4 S2F10 SF6 | ClF ClF3 ClF5 | HArF ArF2 | |||||||||||
KF | CaF2 | ScF3 | TiF3 TiF4 | VF2 VF3 VF4 VF5 | CrF2 CrF3 CrF4 CrF5 CrF6 | MnF2 MnF3 MnF4 | FeF2 FeF3 | CoF2 CoF3 | NiF2 NiF3 | CuF CuF2 | ZnF2 | GaF3 | GeF4 | AsF3 AsF5 | SeF4 SeF6 | BrF BrF3 BrF5 | KrF2 KrF4 KrF6 | |
RbF | SrF2 | YF3 | ZrF4 | NbF4 NbF5 | MoF4 MoF5 MoF6 | TcF6 | RuF3 RuF4 RuF5 RuF6 | RhF3 RhF5 RhF6 | PdF2 Pd[PdF6] PdF4 PdF6 | AgF AgF2 AgF3 Ag2F | CdF2 | InF3 | SnF2 SnF4 | SbF3 SbF5 | TeF4 TeF6 | IF IF3 IF5 IF7 | XeF2 XeF4 XeF6 XeF8 | |
CsF | BaF2 | * | LuF3 | HfF4 | TaF5 | WF4 WF6 | ReF6 ReF7 | OsF4 OsF5 OsF6 OsF 7 OsF8 | IrF3 IrF5 IrF6 | PtF2 Pt[PtF6] PtF4 PtF5 PtF6 | AuF AuF3 Au2F10 AuF5·F2 | HgF2 Hg2F2 HgF4 | TlF TlF3 | PbF2 PbF4 | BiF3 BiF5 | PoF4 PoF6 | At | RnF2 RnF6 |
Fr | RaF2 | ** | Lr | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Nh | Fl | Mc | Lv | Ts | Og |
↓ | ||||||||||||||||||
* | LaF3 | CeF3 CeF4 | PrF3 PrF4 | NdF3 | PmF3 | SmF2 SmF3 | EuF2 EuF3 | GdF3 | TbF3 TbF4 | DyF3 | HoF3 | ErF3 | TmF2 TmF3 | YbF2 YbF3 | ||||
** | AcF3 | ThF4 | PaF4 PaF5 | UF3 UF4 UF5 UF6 | NpF3 NpF4 NpF5 NpF6 | PuF3 PuF4 PuF5 PuF6 | AmF3 AmF4 AmF6 | CmF3 | Bk | Cf | Es | Fm | Md | No |
- AgPF6
- KAsF6
- LiAsF6
- NaAsF6
- HPF6
- HSbF6
- NH4PF6
- KPF6
- KSbF6
- LiPF6
- NaPF6
- NaSbF6
- TlPF6
- Cs2AlF5
- K3AlF6
- Na3AlF6
and pseudohalogenides
- BaSiF6
- BaGeF6
- (NH4)2SiF6
- Na2[SiF6]
- K2[SiF6]
- CBrF3
- CBr2F2
- CBr3F
- CClF3
- CCl2F2
- CCl3F
- CF2O
- CF3I
- CHF3
- CH2F2
- CH3F
- C2Cl3F3
- C2H3F
- C6H5F
- C7H5F3
- C15F33N
- C3H5F
- C6H11F
lanthanide, actinide, ammonium
- VOF3
- CrOF4
- CrF2O2
- NH4F
- (NH4)2ZrF6
- CsXeF7
- Li2TiF6
- Li2ZrF6
- K2TiF6
- Rb2TiF6
- Na2TiF6
- Na2ZrF6
- K2NbF7
- K2TaF7
- K2ZrF6
- UO2F2
- FNO
- FNO2
- FNO3
- KHF2
- NaHF2
- NH4HF2
and iodosyl
- F2OS
- F3OP
- PSF3
- IOF3
- IO3F
- IOF5
- IO2F
- IO2F3