Dr. Anthony Haynes

Department of Chemistry, University of Sheffield


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CHM2104.7/2105.7 Reaction Mechanisms of Transition Metal Complexes

Berry Pseudorotation

The animation shows a trigonal bipyramidal molecule ML5 undergoing Berry pseudorotation. This occurs in, for example, Fe(CO)5, for which 13C NMR spectroscopy cannot distinguish axial and equatorial CO environments, due to the rapid interchange.  The same process can occur in main group compounds like PF5.

The numbering scheme is shown below.

Ligands 2 and 3 move from axial to equatorial positions in the trigonal bipyramid whilst ligands 4 and 5 move from equatorial to axial positions.

Ligand 1 does not move and acts as a pivot.

At the midway point (transition state) ligands 2,3,4,5 are equivalent, forming the base of a square pyramid.

The motion is equivalent to a 90o rotation about the M-L1 axis

PF5 Movie


Snapshots