Phosphorus pentafluoride

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Phosphorus pentafluoride
Structure of the phosphorus pentafluoride molecule
Space-filling model of the phosphorus pentafluoride molecule
Names
IUPAC name
Phosphorus pentafluoride
Other names
Phosphorus(V) fluoride
Pentafluoridophosphorus
Pentafluorophosphorane
Identifiers
7647-19-0 YesY
ChemSpider 22715 N
EC Number 231-602-3
Jmol 3D model Interactive image
PubChem 24295
RTECS number TH4070000
UN number 2198
Properties
PF5
Molar mass 125.966 g/mol
Appearance colourless gas
Odor unpleasant
Density 5.527 kg/m3 (g/L)
Melting point −93.78 °C (−136.80 °F; 179.37 K)
Boiling point −84.6 °C (−120.3 °F; 188.6 K)
hydrolysis
Structure
trigonal bipyramidal
0 D
Hazards
Flash point Non-flammable
Related compounds
Other anions
Phosphorus pentachloride
Phosphorus pentabromide
Phosphorus pentaiodide
Other cations
Arsenic pentafluoride
Antimony pentafluoride
Bismuth pentafluoride
Related compounds
Phosphorus trifluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Phosphorus pentafluoride, PF5, is a phosphorus halide. It is a colourless gas at room temperature and pressure.[1]

Preparation[edit]

Phosphorus pentafluoride was first prepared in 1876 by the fluorination of phosphorus pentachloride using arsenic trifluoride.

Structure[edit]

Single-crystal X-ray studies indicate that the PF5 molecule has two distinct types of P−F bonds (axial and equatorial): the length of an axial P−F bond is same as equatorial P-F bond due to Pseudo Berry Rotation.

Fluorine-19 NMR spectroscopy, even at temperatures as low as −100 °C, fails to distinguish the axial from the equatorial fluorine environments. The apparent equivalency arises from the low barrier for pseudorotation via the Berry mechanism, by which the axial and equatorial fluorine atoms rapidly exchange positions. The apparent equivalency of the F centers in PF5 was first noted by Gutowsky.[2] The explanation was first described by R. Stephen Berry, after whom the Berry mechanism is named. Berry pseudorotation influences the 19F NMR spectrum of PF5 since NMR spectroscopy operates on a millisecond timescale. Electron diffraction and X-ray crystallography do not detect this effect as the solid state structures are, relative to a molecule in solution, static and can not undergo the necessary changes in atomic position.

References[edit]

  1. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9. 
  2. ^ Gutowsky, H. S.; McCall, D. W.; Slichter, C. P. (1953). "Nuclear Magnetic Resonance Multiplets in Liquids". J. Chem. Phys. 21 (2): 279. doi:10.1063/1.1698874.