Phosphorus trifluoride

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Phosphorus trifluoride
Structure and dimensions of phosphorus trifluoride Space-filling model of phosphorus trifluoride
Identifiers
CAS number 7783-55-3 YesY
PubChem 62665
ChemSpider 56416 YesY
ChEBI CHEBI:30205 YesY
RTECS number TH3850000
Jmol-3D images Image 1
Properties
Molecular formula PF3
Molar mass 87.968971 g/mol
Appearance colorless gas
Density 3.91 g/L, gas
Melting point −151.5 °C (−240.7 °F; 121.6 K)
Boiling point −101.8 °C (−151.2 °F; 171.3 K)
Solubility in water slow hydrolysis
Structure
Molecular shape Trigonal pyramidal
Dipole moment 1.03 D
Hazards
MSDS External MSDS
EU Index Not listed
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Related compounds
Other anions Phosphorus trichloride
Phosphorus tribromide
Phosphorus triiodide
Phosphane
Other cations Nitrogen trifluoride
Arsenic trifluoride
Antimony trifluoride
Bismuth trifluoride
Related ligands Carbon monoxide
Related compounds Phosphorus pentafluoride
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Phosphorus trifluoride (formula PF3), is a colorless and odorless gas. It is highly toxic and reacts slowly with water. Its main use is as a ligand in metal complexes. As a ligand it parallels carbon monoxide in metal carbonyls,[1] and indeed its toxicity is due to its binding with the iron in blood hemoglobin in a similar way to carbon monoxide.

Physical properties[edit]

Phosphorus trifluoride has a bond angle of 107°, F-P-F bond angle being 96.3°. Gaseous PF3 has a standard enthalpy of formation of -945 kJ/mol (-226 kcal/mol). The phosphorus atom has an nuclear magnetic resonance chemical shift of 97 ppm (downfield of H3PO4).

Properties[edit]

Phosphorus trifluoride hydrolyzes especially at 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 metals, phosphides and fluorides are formed. With Lewis bases such as ammonia addition products (adducts) are formed, and PF3 is oxidized by oxidizing agents such as bromine or potassium permanganate.

As a ligand for transition metals, PF3 is a strong π-acceptor.[2] It forms a variety of metal complexes with metals in low oxidation states. PF3 forms several complexes for which the corresponding CO derivatives (see metal carbonyl) are unstable or nonexistent. Thus, Pd(PF3)4 is known, but Pd(CO)4 is not.[3][4][5] Such complexes are usually prepared directly from the related metal carbonyl compound, with loss of CO. However, Nickel metal reacts directly with PF3 at 100 °C under 35 MPa pressure to form Ni(PF3)4, which is analogous to Ni(CO)4. Cr(PF3)6, the analogue of Cr(CO)6, may be prepared from dibenzenechromium:

Cr(C6H6)2 + 6 PF3 → Cr(PF3)6 + 2 C6H6
Tetrakis(trifluorophosphine)platinum(0)-from-xtal-2008-3D-balls.png
Tetrakis(trifluorophosphine)platinum(0)-from-xtal-2008-3D-SF.png
Ball-and-stick model of [Pt(PF3)4]
Space-filling model of [Pt(PF3)4]

Preparation[edit]

Phosphorus trifluoride is usually prepared from phosphorus trichloride via halogen exchange using various fluorides such as hydrogen fluoride, calcium fluoride, arsenic trifluoride, antimony trifluoride, or zinc fluoride:[6][7][8]

2 PCl3 + 3 ZnF2 → 2 PF3 + 3 ZnCl2

Biological activity[edit]

Phosphorus trifluoride is similar to carbon monoxide in that it is a gas which strongly binds to iron in hemoglobin, preventing the blood from absorbing oxygen.

Precautions[edit]

PF3 is highly toxic, comparable to phosgene.[9]

References[edit]

  1. ^ Chatt, J. (1950). "The Co-Ordinate Link in Chemistry". Nature 165 (4199): 637–638. doi:10.1038/165637a0. PMID 15416738. 
  2. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 494. ISBN 0080379419. 
  3. ^ Nicholls, D. (1973). Complexes and First-Row Transition Elements. London: Macmillan Press. 
  4. ^ Kruck, T. (1967). "Trifluorphosphin-Komplexe von Übergangsmetallen". Angewandte Chemie 79 (1): 27–43. doi:10.1002/ange.19670790104. 
  5. ^ Clark, R. J.; Busch, M. A. (1973). "Stereochemical Studies of Metal Carbonyl-Phosphorus Trifluoride Complexes". Accounts of Chemical Research 6 (7): 246–252. doi:10.1021/ar50067a005. 
  6. ^ Williams, A. A.; Parry, R. W.; Dess, H. (1957). "Phosphorus(III) Fluoride". Inorganic Syntheses 5: 95–97. doi:10.1002/9780470132364.ch26. 
  7. ^ Dubrisay, R. (1956). Pascal, P., ed. Azote-Phosphore. Nouveau Traité de Chimie Minérale 10. Paris, France: Masson. ISBN 978-2-225-57123-7. 
  8. ^ Clark, R. J.; Belefant, H.; Williamson, S. M. (1990). "Phosphorus Trifluoride". Inorganic Syntheses 28: 310–315. doi:10.1002/9780470132593.ch77. ISBN 978-0-470-13259-3. 
  9. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419. 

Further reading[edit]

External links[edit]