Phosphorus trifluoride
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{{Chembox new
| Name = Phosphorus trifluoride
| ImageFile = Phosphorus-trifluoride-2D-dimensions.png
<!-- | ImageSize = 150px -->
| ImageName = Phosphorus trifluoride
| ImageFile1 = Phosphorus-trifluoride-3D-vdW.png
<!-- | ImageSize1 = 150px -->
| ImageName1 = Phosphorus trifluoride
| IUPACName = Phosphorus trifluoride<br />Phosphorus(III) fluoride<br />Trifluorophosphane<br />Trifluorophosphorus
| OtherNames = Trifluorophosphine
| Section1 = {{Chembox Identifiers
| CASNo = 7783-55-3
}}
| Section2 = {{Chembox Properties
| Formula = PF<sub>3</sub>
| MolarMass = 87.98 g/mol
| Appearance = colorless gas
| Density = 3.91 g/l, gas
| Solubility = <br />slow hydrolysis
| MeltingPt = −151.5 °C (121.7 K)
| BoilingPt = −101.8 °C (171.4 K)
| pKb =
}}
| Section3 = {{Chembox Structure
| MolShape = pyramidal
| Dipole = 1.03 [[Debye|D]]
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS =
| EUClass = not listed
| FlashPt = non-flammable
}}
| Section8 = {{Chembox Related
| OtherAnions = [[Phosphorus trichloride]]<br />[[Phosphorus tribromide]]<br />[[Phosphorus triiodide]]
| OtherCations = [[Nitrogen trifluoride]]<br />[[Arsenic trifluoride]]
| Function = [[ligand]]s
| OtherFunctn = [[Carbon monoxide]]
| OtherCpds = [[Phosphorus pentafluoride]]
}}
}}
'''Phosphorus trifluoride''' (formula [[Phosphorus|P]][[Fluorine|F]]<sub>3</sub>, is a colourless and odourless [[gas]]. It is highly toxic and it reacts slowly with water. Its main use is as a [[ligand]] in [[Complex (chemistry)|metal complexes]]. As a ligand it parallels [[carbon monoxide]]<ref name="ref6">J. Chatt, ''Nature'' '''165''', 637-8 (1950).</ref> in [[metal carbonyl]]s, and indeed its toxicity is due to the fact that it binds with the [[iron]] in blood [[hemoglobin|haemoglobin]] in a similar way to carbon monoxide.
==Physical properties==
Phosphorus trifluoride has a bond angle of 96.3°. [[Gas]]eous PF<sub>3</sub> has a [[standard enthalpy change of formation|standard enthalpy of formation]] of -945 kJ/mol (-226 [[Calorie|kcal]]/ [[mole (unit)|mol]]). The phosphorus atom has an [[Nuclear magnetic resonance|NMR]] chemical shift of 97 ppm (downfield of [[phosphoric acid|H<sub>3</sub>PO<sub>4</sub>]]).
==Properties==
Phosphorus trifluoride [[Hydrolysis reaction|hydrolyses]] especially at [[Alkali|high pH]], but it is less hydrolytically sensitive than [[phosphorus trichloride]]. It does not attack glass except at high temperatures, and anhydrous [[potassium hydroxide]] may be used to dry it with little loss. With hot [[metal]]s, phosphides and fluorides are formed. With [[Lewis base]]s such as [[ammonia]] addition products (adducts) are formed, and PF<sub>3</sub> is oxidised by [[Redox|oxidising agent]]s such as [[bromine]] or [[potassium permanganate]].
As a ligand for transition metals, PF<sub>3</sub> is a strong π-acceptor.<ref name="ref1 p494">N. N. Greenwood, A. Earnshaw, ''Chemistry of the Elements'', 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997, p 494</ref> It forms a variety of [[Complex (chemistry)|metal complexes]] with [[metal]]s in low [[oxidation state]]s. PF<sub>3</sub> forms several complexes for which the corresponding CO derivatives (see [[metal carbonyl]]) are unstable or nonexistent. Thus, Pd(PF<sub>3</sub>)<sub>4</sub> is known, but Pd(CO)<sub>4</sub> is not.<ref name="ref9">D. Nicholls, ''Complexes and First-Row Transition Elements'', Macmillan Press, London, 1973.</ref><ref name="ref10">Kruck, T.“Trifluorphosphin-Komplexe von Übergangsmetallen” Angewandte Chemie 1967, volume 79, p 27-43. DOI: 10.1002/ange.19670790104</ref><ref> Clark, R. J.; Busch, M. A. “Stereochemical studies of metal carbonylphosphorus trifluoride complexes” Accounts of Chemical Research, 1973, volume 6, pages 246-52.DOI: 10.1021/ar50067a005.</ref> Such complexes are usually prepared directly from the related [[metal carbonyl]] compound, with loss of [[Carbon monoxide|CO]]. However, [[Nickel]] [[metal]] reacts directly with PF<sub>3</sub> at 100 °C under 35 [[Pascal (unit)|MPa]] pressure to form Ni(PF<sub>3</sub>)<sub>4</sub>, which is analogous to [[Nickel carbonyl|Ni(CO)<sub>4</sub>]]. Cr(PF<sub>3</sub>)<sub>6</sub>, the analogue of [[Chromium hexacarbonyl|Cr(CO)<sub>6</sub>]], may be prepared from [[dibenzenechromium]]:
:[[Dibenzenechromium|Cr(C<sub>6</sub>H<sub>6</sub>)<sub>2</sub>]] + 6PF<sub>3</sub> → Cr(PF<sub>3</sub>)<sub>6</sub> + 2[[Benzene|C<sub>6</sub>H<sub>6</sub>]]
==Preparation==
Phosphorus trifluoride is usually prepared from [[phosphorus trichloride]] via halogen exchange using various [[fluoride]]s, e.g. [[hydrogen fluoride]], [[calcium fluoride]], [[arsenic trifluoride]], [[antimony trifluoride]], or [[zinc fluoride]]:<ref>A. A. Williams, in ''Inorganic Syntheses'', Vol. V, 95-7 (1946).</ref><ref>''Nouveau traité de chimie minérale : Tome X'', Masson, Paris, France, 1956.</ref><ref>{{cite journal | author = Ronald J. Clark, Helen Belefant, Stanley M. Williamson | title = Phosphorus Trifluoride | journal = [[Inorganic Syntheses]] | volume = 28 | pages = 310–315 | doi = 10.1002/9780470132593.ch77 | year = 1990}}</ref>
:2[[Phosphorus trichloride|PCl<sub>3</sub>]] + 3[[Zinc fluoride|ZnF<sub>2</sub>]] → 2PF<sub>3</sub> + 3[[Zinc chloride|ZnCl<sub>2</sub>]]
==Biological activity==
Phosphorus trifluoride is similar to [[carbon monoxide]] in that it is a gas which strongly binds to [[iron]] in [[haemoglobin]], preventing the blood from absorbing oxygen.
==Precautions==
PF<sub>3</sub> is highly [[poison|toxic]], comparable to [[phosgene]].<ref>Greenwood, 1997</ref>
==External links==
*[http://www.npi.gov.au/database/substance-info/profiles/44.html National Pollutant Inventory - Flouride and compounds fact sheet]
==References==
{{Citationstyle|date=September 2007}}
<references/>
* ''Handbook of Chemistry and Physics'', 71st edition, CRC Press, Ann Arbor, Michigan, 1990.
* J. March, ''Advanced Organic Chemistry'', 4th ed., p. 723, Wiley, New York, 1992.
* ''The Merck Index'', 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960.
* A. D. F. Toy, ''The Chemistry of Phosphorus'', Pergamon Press, Oxford, UK, 1973.
[[Category:Phosphorus compounds]]
[[Category:Fluorides]]
[[Category:Nonmetal halides]]
[[de:Phosphor(III)-fluorid]]