- Sulfur tetrafluoride
Chembox new
Name = Sulfur tetrafluoride
ImageFile = Sulfur-tetrafluoride-2D-dimensions.png
ImageName = Sulfur tetrafluoride
ImageFile1 = Sulfur-tetrafluoride-3D-balls.png
ImageName1 = Sulfur tetrafluoride
ImageFile2 = Sulfur-tetrafluoride-3D-vdW.png
ImageName2 = Sulfur tetrafluoride
IUPACName = Sulfur(IV) fluoride
OtherNames = Sulfur tetrafluoride
Section1 = Chembox Identifiers
CASNo = 7783-60-0
RTECS = WT4800000
Section2 = Chembox Properties
Formula = SF4
MolarMass = 108.07 g/mol
Appearance = colorless gas
Density = 1.95 g cm−3, −78 °C
Solubility = decomp
MeltingPt = −121.0 °C
BoilingPt = −38 °C
Section3 = Chembox Structure
Coordination = C2v
Dipole = 0.632 D [Tolles; W. M. Gwinn, W. D. “Structure and Dipole Moment for SF4” The Journal of Chemical Physics 1962, Volume 36, pp. 1119-1121. DOI|10.1063/1.1732702]
Section7 = Chembox Hazards
ExternalMSDS =
MainHazards = highly toxic
corrosive
NFPA-H = 4
NFPA-F = 0
NFPA-R = 2
NFPA-O = W
RPhrases = 14-26-34-37
SPhrases = 26-36/37/39-38-45
Section8 = Chembox Related
OtherCpds = SeF4
SF6
SCl2
S2Cl2
Me2NSF3Sulfur tetrafluoride is the
chemical compound with the formula SF4. This species exists as a gas at standard conditions. It is a corrosive species that releases dangerous HF upon exposure to water or moisture. Despite these unwelcome characteristics, this compound is a usefulreagent for the preparation of organofluorine compounds, [C.-L. J. Wang, "Sulfur Tetrafluoride" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.] some of which are important in the pharmaceutical and specialty chemical industries. Aside from SF4, two other binary sulfur fluorides are well known, SF6 and S2F10.tructure of the SF4 molecule
Sulfur in SF4 is in the formal 4+
oxidation state . Of sulfur's total of sixvalence electron s, two form a "lone pair." The structure of SF4 can therefore be anticipated using the principles ofVSEPR theory : it is a see-saw shape, with S at the center. One of the three equatorial positions is occupied by a nonbondinglone pair of electrons. Ignoring this lone pair, SF4 has asee-saw molecular geometry . Consequently, the molecule has two distinct types of F ligands, twoaxial and twoequatorial . The relevant bond distances are S-Fax = 1.643 Å and S-Feq = 1.542 Å. It is typical for the axial ligands inhypervalent 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.The19F NMR spectrum of SF4 reveals only one signal, which indicates that the axial and equatorial F atom positions rapidly interconvert via "pseudorotation." [Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.]
ynthesis and manufacture
SF4 is produced by the reaction of SCl2, Cl2, and NaF::: SCl2 + Cl2 + 4NaF → SF4 + 4NaClInterestingly, treatment of SCl2 with NaF also affords SF4, not SF2. SF2 is unstable, it condenses with itself to form SF4 and SSF2.
Use of SF4 for the synthesis of fluorocarbons
In
organic synthesis , SF4 is used to convert COH and C=O groups into CF and CF2 groups, respectively. [W. R. Hasek "1,1,1-Trifluoroheptane" Organic Syntheses, Coll. Vol. 5, p.1082; Vol. 41, p.104. http://www.orgsyn.org/orgsyn/pdfs/CV5P1082.pdf] Certainalcohol s readily give the correspondingfluorocarbon .Ketones andaldehydes give geminal difluorides. The presence of protons alpha to the carbonyl leads to side reactions and diminished (30- 40%) yield. Also diols can give cyclic sulfite esters, (RO)2SO. Carboxylic acids convert to trifluoromethyl derivatives. For example treatment of heptanoic acid with SF4 at 100-130 °C produces 1,1,1-trifluoroheptane. The coproducts from these fluorinations, including unreacted SF4 together with SOF2 and SO2, are toxic but can be neutralized by their treatment with aqueous KOH.The use of SF4 is being superseded in recent years by the more conveniently handled
diethylaminosulfur trifluoride , Et2NSF3, "DAST," where Et = CH3CH2. [A. H. Fauq, "N,N-Diethylaminosulfur Trifluoride" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.] This reagent is prepared from SF4: [W. J. Middleton, E. M. Bingham" Diethylaminosulfur Trifluoride” Organic Syntheses, Coll. Vol. 6, p.440; Vol. 57, p.50.http://www.orgsyn.org/orgsyn/pdfs/CV6P0440.pdf] :: SF4 + Me3SiNEt2 → Et2NSF3 + Me3SiFReferences
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