Thiophosphoryl fluoride - Misplaced Pages

Thiophosphoryl fluoride is an inorganic molecular gas with formula P S F₃ containing phosphorus, sulfur and fluorine. It spontaneously ignites in air and burns with a cool flame. The discoverers were able to have flames around their hands without discomfort, and called it "probably one of the coldest flames known". The gas was discovered in 1888.

It is useless for chemical warfare as it burns immediately and is not toxic enough.

Preparation

Thiophosphoryl fluoride was discovered and named by J. W. Rodger and T. E. Thorpe in 1888.

They prepared it by heating arsenic trifluoride and thiophosphoryl chloride together in a sealed glass tube to 150 °C. Also produced in this reaction was silicon tetrafluoride and phosphorus fluorides. By increasing the PSCl₃ the proportion of PSF₃ was increased. They observed the spontaneous inflammability. They also used this method:

3 PbF₂ + P₂S₅ → 3 PbS + PSF₃

at 170 °C, and also substituting a mixture of red phosphorus and sulfur, and substituting bismuth trifluoride.

Another way to prepare PSF₃ is to add fluoride to PSCl₃ using sodium fluoride in acetonitrile.

A high yield reaction can be used to produce the gas:

P₄S₁₀ + 12 HF → 6 H₂S + 4 PSF₃

Under high pressure phosphorus trifluoride can react with hydrogen sulfide to yield:

PF₃ + H₂S → PSF₃ + H₂ (1350 bar at 200 °C)

Another high pressure production uses phosphorus trifluoride with sulfur.

Reactions

PSF₃ is unstable against moisture or heat. The pure gas is completely absorbed by alkali solutions, producing the fluoride and a thiophosphate (PSO3−3), but stable against CaO. The latter can be used to remove SiF₄ or PF₃ impurities.

Hydrolysis and decomposition

Reaction with neutral water is slow:

PSF₃ + 4 H₂O → H₂S + H₃PO₄ + 3 HF

Nevertheless, dissociation constants for related acids suggest that the phosphorus atom is at least as electrophilic as in phosphoryl fluoride.

Autodecomposition from heat gives phosphorus fluorides, sulfur, and phosphorus:

PSF₃ → S + PF₃ → ...

Hot PSF₃ reacts with glass, producing SF₄, sulfur and elemental phosphorus. If water is present and the glass is leaded, then the hydrofluoric acid and hydrogen sulfide combination produces a black plumbous sulfide deposit on the inner surface.

Oxidation

In air, PSF₃ burns spontaneously with a greyish green flame, producing solid white fumes containing SO₂ and P₂O₅. The flame is one of the coldest known. With dry oxygen, combustion may not be spontaneous and the flame is yellow.

Thiophosphoryl fluoride reduces oxygenated compounds to give phosphoryl fluoride and sulfur:

PSF₃ + SO₃ → POF₃ + SO₂

2 PSF₃ + SO₂ → 2 POF₃ + 3 S

The latter reaction also indicates why PSF₃ is not formed from PF₃ and SO₂.

Various oxidants can convert thiophosphoryl fluoride to phosphorus dichloride trifluoride, e.g.:

PSF₃ + 2 ICl → PCl₂F₃ + I₂ + S.

Nucleophilic substitution

Thiophosphoryl difluoride isocyanate can be formed by reacting PSF₃ with silicon tetraisocyanate at 200 °C in an autoclave.

In general, nucleophilic substitution onto thiophosphoryl fluoride is complex, because free fluoride ions tend to induce disproportionation to hexafluorophosphate and dithiodifluorophosphate (PS₂F−2). For example, with cesium fluoride:

CsF + 2 PSF₃ → Cs[PF₆] + CsPS₂F₂

Thus PSF₃ combines with dimethylamine in solution to produce dimethylaminothiophosphoryl difluoride (H₃C−)₂N−P(=S)F₂ and difluorophosphate and hexafluorophosphate ions:

4 SPF₃ + 4 HNMe₂ → 2 SPF₂NMe₂ + PF₆ + S₂PF₂.

PSF₃ reacts with four times its volume of ammonia gas producing ammonium fluoride and a mystery product, possibly P(NH₂)₂SF.

Miscellaneous

PSF₃ does not react with ether, benzene, carbon disulfide, or pure sulfuric acid. It initiates tetrahydrofuran polymerization.

PSF₃ reacts with [SF₆] in a mass spectrometer to form [PSF₄].

PSF₃ + [SF₆] → PSF₄ + SF₅

Related compounds

One fluorine can be substituted by iodine to give thiophosphoryl difluoride iodide, PSIF₂. PSIF₂ can be converted to hydrothiophosphoryldifluoride, S=PHF₂, by reducing it with hydrogen iodide. In F₂P(=S)−S−PF₂, one sulfur forms a bridge between two phosphorus atoms.

Dimethylaminothiophosphoryl difluoride ((H₃C−)₂N−P(=S)F₂) is a foul smelling liquid with a boiling point of 117 °C. It has a Trouton constant (entropy of vaporization at the boiling point of the liquid) of 24.4, and a heat of evaporation of 9530 cal/mole. Alternately it can be produced by fluorination of dimethylaminothiophosphoryl dichloride ((H₃C−)₂N−P(=S)Cl₂).

Physical properties

The thiophosphoryl trifluoride molecule shape has been determined using electron diffraction. The interatomic distances are P=S 0.187±0.003 nm, P−F 0.153±0.002 nm and bond angles of F−P−F bonding is 100.3±2°, The microwave rotational spectrum has been measured for several different isotopologues.

The critical point is at 346 K at 3.82 MPa. The liquid refractive index is 1.353.

The enthalpy of vaporisation 19.6 kJ/mol at boiling point. The enthalpy of vaporisation at other temperatures is a function of temperature T: H(T)=28.85011(346-T) kJ/mol.

The molecule is polar. It has a non-uniform distribution of positive and negative charge which gives it a dipole moment. When an electric field is applied more energy is stored than if the molecules did not respond by rotating. This increases the dielectric constant. The dipole moment of one molecule of thiophosphoryl trifluoride is 0.640 Debye.

The infrared spectrum includes vibrations at 275, 404, 442, 698, 951 and 983 cm. These can be used to identify the molecule.

References

^ A likely spelling mistake in Handbook of Chemistry and Physics 87 ed
"FP(F)(F)=S".
"phosphorothioic trifluoride".
^ "Phosphorothioic trifluoride-(2404-52-6)-Chemical Dictionary-hgspace.com". Archived from the original on 2016-03-03. Retrieved 2012-01-29.
^ Thorpe, T. E.; Rodger, J. W. (1889). "XXXIV.?On thiophosphoryl fluoride". Journal of the Chemical Society, Transactions. 55: 306–323. doi:10.1039/CT8895500306.
Banks, Ronald Eric (2000). Fluorine chemistry at the millennium: fascinated by fluorine. Elsevier. p. 502. ISBN 0-08-043405-3.
Thorpe, T. E.; Rodger, J. W. (1888). "LX.?Thiophosphoryl fluoride". Journal of the Chemical Society, Transactions. 53: 766–767. doi:10.1039/CT8885300766.
Padma, D. K.; Vijayalakshmi, S. K.; Vasudevamurthy, A. R. (1976). "Investigations on the preparation, oxidation and reduction reactions of thiophosphoryl fluoride". Journal of Fluorine Chemistry. 8 (6): 461. doi:10.1016/S0022-1139(00)81660-7.
^ Hagen, Arnulf P.; Callaway, Bill W. (1978). "High-pressure reactions of small covalent molecules. 10. The reaction of phosphorus trifluoride with hydrogen sulfide and sulfur dioxide". Inorganic Chemistry. 17 (3): 554. doi:10.1021/ic50181a007.
^ Almasi, Lucreţia (1971). "The Sulfur–Phosphorus Bond". In Senning, Alexander (ed.). Sulfur in Organic and Inorganic Chemistry. Vol. 1. New York: Marcel Dekker. pp. 79, 81. ISBN 0-8247-1615-9. LCCN 70-154612. Note the typo on p. 81: the final species in the final display should be PS₂F
₂.
Sampath Kumar, H.P.; Padma, D.K.; Vasudeva Murthy, A.R. (1984). "Reaction of thiophosphoryl fluoride with sulphur trioxide". Journal of Fluorine Chemistry. 26: 117–123. doi:10.1016/S0022-1139(00)85125-8.
Sampath Kumar, H.P.; Padma, D.K. (1990). "Reaction of phosphorus trifluoride and thiophosphoryl fluoride with iodine monochloride and oxidation of phosphorus trifluoride with nitryl chloride, iodic acid, periodic acid, sodium nitrite and potassium nitrite". Journal of Fluorine Chemistry. 49 (3): 301. doi:10.1016/S0022-1139(00)85026-5.
Roesky, H.W. (1970). "Thiophosphoryl-difluoride-isocyanate". Journal of Inorganic and Nuclear Chemistry. 32 (6): 1845–1846. doi:10.1016/0022-1902(70)80591-7.
Islam, Mohammad Q.; Hill, William E.; Webb, Thomas R. (1990). "Quadruply bonded dimolybdenum complexes of PF₂S₂−. Comparison with complexes of PR₂S₂ (R = Et, Me)". Journal of Fluorine Chemistry. 48 (3): 429. doi:10.1016/S0022-1139(00)80227-4.
Roesky, Herbert W.; Tebbe, Fred N.; Muetterties, Earl L. (1970). "Thiophosphate chemistry. Anion set X₂PS₂, (XPS₂)2S, and (XPS₂)2S₂". Inorganic Chemistry. 9 (4): 831. doi:10.1021/ic50086a028.
Cavell, R. G. (1968). "Chemistry of phosphorus fluorides. Part III. The reaction of thiophosphoryl-fluoride with dimethylamine and some properties of the dimethylaminothio- phosphoryl fluorides". Canadian Journal of Chemistry. 46 (4): 613–621. doi:10.1139/v68-100.
Padma, D.K.; Vijayalakshmi, S.K. (1978). "Thiophosphoryl fluoride and phosphoryl fluoride as initiators for the polymerisation of tetrahydrofuran". Journal of Fluorine Chemistry. 11: 51–56. doi:10.1016/S0022-1139(00)81597-3.
Rhyne, T; Dillard, J (1971). "Reactions of gaseous inorganic negative ions: III. SF₆ with POF₃ and PSF₃". International Journal of Mass Spectrometry and Ion Physics. 7 (5): 371. Bibcode:1971IJMSI...7..371R. doi:10.1016/0020-7381(71)85003-9.
^ Charlton, Thomas L.; Cavell, Ronald G. (1969). "Difluorothiophosphoryl-μ-thio-difluorophosphine and difluorophosphoryl-μ-oxo-difluorophosphine. Novel mixed-valence fluorophosphorus compounds". Inorganic Chemistry. 8 (11): 2436. doi:10.1021/ic50081a037.
Charlton, Thomas L.; Cavell, R. G. (1968). "Preparation and properties of iodothiophosphoryl difluoride, SPF₂I". Inorganic Chemistry. 7 (11): 2195. doi:10.1021/ic50069a005.
Williams, Quitman; Sheridan, John; Gordy, Walter (1952). "Microwave Spectra and Molecular Structures of POF₃, PSF₃, POCl₃, and PSCl₃". The Journal of Chemical Physics. 20 (1): 164–167. Bibcode:1952JChPh..20..164W. doi:10.1063/1.1700162.
Handbook of Chemistry and Physics 87 ed page 6-39
Mattox, D. M. (2003-12-31). The foundations of vacuum coating technology. Elsevier Science. p. 550. ISBN 978-0-8155-1495-4.
Mattox, D. M. (2003-12-31). The foundations of vacuum coating technology. Elsevier Science. p. 406. ISBN 978-0-8155-1495-4.
Mattox, D. M. (2003-12-31). The foundations of vacuum coating technology. Elsevier Science. p. 685. ISBN 978-0-8155-1495-4.
Cavell, R (1967). "The infrared spectrum of thiophosphoryl fluoride". Spectrochimica Acta Part A: Molecular Spectroscopy. 23 (2): 249–256. Bibcode:1967AcSpA..23..249C. doi:10.1016/0584-8539(67)80227-7.

Other references

Humphries, C. M.; Walsh, A. D.; Warsop, P. A. (1963). "Absorption spectrum of chlorine dioxide in the vacuum ultra-violet". Transactions of the Faraday Society. 35: 137. doi:10.1039/df9633500137.
Montana, Anthony J.; Zumbulyadis, Nikolaos; Dailey, Benjamin P. (1976). "19F and 31P magnetic shielding anisotropies and the F–P–F bond angle of PSF3 in a smectic liquid crystal solvent". The Journal of Chemical Physics. 65 (11): 4756. Bibcode:1976JChPh..65.4756M. doi:10.1063/1.432929.
Hawkins, Norval John (1951). The structure of PSF3 and POF3 from microwave spectroscopy.
Chase, M. W. (1998). "Thiophosphoryl fluoride". NIST. pp. 1–1951.
Williams, Quitman; Sheridan, John; Gordy, Walter (1952). "Microwave Spectra and Molecular Structures of POF3, PSF3, POCl3, and PSCl3". The Journal of Chemical Physics. 20 (1): 164–167. Bibcode:1952JChPh..20..164W. doi:10.1063/1.1700162.
Lange, Willy; Askitopoulos, Konstantin (1938). "Zur Kenntnis des Phosphorsulfotrifluorids PSF3 und über ein Salz der Thiodifluorphosphorsäure H\PSF2O]". Berichte der Deutschen Chemischen Gesellschaft (A and B Series). 71 (4): 801. doi:10.1002/cber.19380710419.
Poulenc, C. (1891). "Comptes rendus hebdomadaires des séances de l'Académie des sciences / Publiés... Par MM. Les secrétaires perpétuels". Comptes Rendus. 113: 75.

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