Phosphorus pentafluoride

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
CAS Number	7647-19-0 Y
ChemSpider	22715 N
EC Number	231-602-3
Jmol 3D model	Interactive image
PubChem	24295
RTECS number	TH4070000
UN number	2198
InChI InChI=1S/F5P/c1-6(2,3,4)5 N Key: OBCUTHMOOONNBS-UHFFFAOYSA-N N InChI=1/F5P/c1-6(2,3,4)5 Key: OBCUTHMOOONNBS-UHFFFAOYAH
SMILES FP(F)(F)(F)F
Properties
Chemical formula	PF5
Molar mass	125.966 g/mol
Appearance	colourless gas
Odor	unpleasant
Density	5.527 g/cm3
Melting point	−93.78 °C (−136.80 °F; 179.37 K)
Boiling point	−84.6 °C (−120.3 °F; 188.6 K)
Solubility in water	hydrolysis
Structure
Molecular shape	trigonal bipyramidal
Dipole moment	0 D
Vapor pressure	{{{value}}}
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 YN ?)
Infobox references

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

Preparation

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

Structure

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 158.0 pm and the length of an equatorial P−F bond is 152.2 pm. Gas-phase electron diffraction analysis gives similar values: the axial P−F bonds are 158 pm long and the equatorial P−F bonds are 153 pm long.

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. 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.