Sulfur tetrafluoride

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| Watchedfields = changed
| verifiedrevid = 450644265
| Name = Sulfur tetrafluoride
| ImageFile = Sulfur tetrafluoride 2D dimensions. png
| ImageName = Structural formula of sulfur tetrafluoride, showing dimernsions
| ImageFileL2 = Sulfur tetrafluoride 3D balls. png
| ImageNameL2 = Ball and stick model of sulfur tetrafluoride
| ImageFileR2 = Sulfur tetrafluoride 3D vdW. png
| ImageNameR2 = Space filling model of sulfur tetrafluoride
| IUPACName = Sulfur(IV) fluoride
| OtherNames = Sulfur tetrafluoride
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|Section2=
|Section7=Chembox Hazards
| ExternalSDS = ICSC 1456
| MainHazards = highly toxiccorrosive
| NFPA H = 3
| NFPA F = 0
| NFPA R = 2
| NFPA S = W
| HPhrases =
| PPhrases =
| GHS ref =
| IDLH = N. D.
| PEL = none some of which are important in the pharmaceutical and specialty chemical industries.

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.