ax = axial ligands (on unique axis)
eq = equatorial ligand (in plane perpendicular to unique axis)
The Berry mechanism, or Berry pseudorotation mechanism, is a type of vibration causing molecules of certain geometries to isomerize by exchanging the two axial ligands (see the figure) for two of the equatorial ones. It is the most widely accepted mechanism for pseudorotation and most commonly occurs in trigonal bipyramidal molecules such as PF5, though it can also occur in molecules with a square pyramidal geometry.[1] The Berry mechanism is named after R. Stephen Berry, who first described this mechanism in 1960.[2][3]
- ^ "Pseudorotation". The IUPAC Compendium of Chemical Terminology. 2014. doi:10.1351/goldbook.P04934.
- ^ R. S. Berry, 1960, "Correlation of rates of intramolecular tunneling processes, with application to some Group V compounds", J. Chem. Phys. 32:933–938, doi:10.1063/1.1730820; accessed 28 May 2014.
- ^ M. Cass, K. K. Hii, H. S. Rzepa, 2005, "Mechanisms that interchange axial and equatorial atoms in fluxional processes: Illustration of the Berry pseudorotation, the turnstile and the lever mechanisms via animation of transition state normal vibrational modes", J. Chem. Educ. (online), 2005. Archived 2019-10-19 at the Wayback Machine; accessed 28 May 2014.