Thionyl tetrafluoride

Thionyl tetrafluoride, also known as sulfur tetrafluoride oxide, is an inorganic compound with the formula SOF₄. It is a colorless gas.

Thionyl tetrafluoride

Structure of thionyl tetrafluoride
Ball-and-stick model of thionyl tetrafluoride Space-filling model of thionyl tetrafluoride
Names
IUPAC name Thionyl tetrafluoride
Identifiers
CAS Number	13709-54-1 Y
3D model (JSmol)	Interactive image
ChemSpider	123077 Y
PubChem CID	139557
CompTox Dashboard (EPA)	DTXSID30160060
InChI InChI=1S/F4OS/c1-6(2,3,4)5 N Key: DUGWRBKBGKTKOX-UHFFFAOYSA-N N
SMILES O=S(F)(F)(F)F
Properties
Chemical formula	SOF4
Molar mass	124.05 g·mol−1
Appearance	colorless gas
Density	1.653−0.0036T (°C) liquid[1]
Melting point	−99.6 °C (−147.3 °F; 173.6 K)
Boiling point	−49 °C (−56 °F; 224 K) 5090 cal/mol heat of vapourisation[1]
Solubility in water	reaction in water
log P	7.2349−859.58/T−26275/T²[1]
Structure
Molecular shape	distorted trigonal bipyramid
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H300, H310, H314, H330
Precautionary statements	P260, P262, P264, P270, P271, P280, P284, P301+P310, P301+P330+P331, P302+P350, P303+P361+P353, P304+P340, P305+P351+P338, P310, P320, P321, P322, P330, P361, P363, P403+P233, P405, P501
Related compounds
Related oxohalides	Thionyl fluoride Selenyl tetrafluoride
Related compounds	Phosphoryl trifluoride Pentafluorosulfur hypofluorite Sulfuryl fluoride Sulfur hexafluoride Thiazyl trifluoride Chromium oxytetrafluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

The shape of the molecule is a distorted trigonal bipyramid, with the oxygen found on the equator. The atoms on the equator have shorter bond lengths than the fluorine atoms on the axis. In the gas-phase, the sulfur-oxygen bond is 1.409 Å. The S−F bond on the axis has length 1.596 Å and the S−F bond on the equator has length 1.539 Å. The angle between the equatorial fluorine atoms is 112.8°. The angle between axial fluorine and oxygen is 97.7°. The angle between oxygen and equatorial fluorine is 123.6° and between axial and equatorial fluorine is 85.7°.^[2] Slight variations of bonds lengths and angles has been observed in solid-state by X-ray analysis.^[3] The fluorine atoms only produce one NMR line, probably because they exchange positions.^[1] It is isoelectronic with phosphorus pentafluoride.

Formation

Thionyl fluoride reacting with fluorine gas can produce thionyl tetrafluoride.^[1] This was how the gas was first discovered by Moissan and Lebeau in 1902. They identified the formula by the pressure changes resulting from the reaction. Silver fluoride and platinum are capable of catalyzing the reaction.

It can also be formed the reaction of silver difluoride with thionyl fluoride at 392 °F (200 °C),^[4] or by electrolyzing hydrogen fluoride with a solution of sulfur dioxide, which also made oxygen difluoride and sulfuryl fluoride. Thionyl chloride or thionyl fluoride electrolyzed with hydrogen fluoride produced even more of the gas.^[5]

Reactions

Thionyl tetrafluoride reacts with water to make hydrofluoric acid, sulfurofluoridic acid, and sulfuryl difluoride. Mercury can strip off fluoride to make thionyl fluoride and mercurous fluoride. Strong bases result in formation of fluoride and fluorosulfate ions.^[1]

Reactions with the strong Lewis acids, such as AsF₅ and SbF₅, result in the formation of trifluorosulfoxonium cation [SOF₃]⁺ and the corresponding salts [SOF₃]⁺[AsF₆]⁻ (trifluorosulfoxonium hexafluoroarsenate(V)) and [SOF₃]⁺[SbF₆]⁻ (trifluorosulfoxonium hexafluoroantimonate(V)), respectively.^[6]

Click chemistry

Thionyl tetrafluoride can be used in click chemistry through reactions with primary amines known as sulfur(VI) fluoride exchange (SuFEx).^[7] This kind of reaction was the first "click" reaction to generate a three-dimensional core.