3D model (JSmol)
|Molar mass||125.966 g/mol|
|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)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
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 distinct from the equatorial P-F bond in the solid phase, but not the liquid or gas phases 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. 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.