20 Mar 2010

The Berry Pseudorotation in PF5

In-Class Activity

Submitted by Maggie Geselbracht, Reed College
Course Level: 

This activity makes use of Jmol animations created by Prof. Marion Cass at Carleton College to illustrate the Berry Pseudorotation in trigonal bipyramidal molecules such as PF5.  Students explore the animations and answer a series of questions that lead to a description of this intramolecular motion that exchanges equatorial and axial atoms in trigonal bipyramidal molecules.  

Link to Jmol animations of Berry Pseudorotation

Link to paper by Marion Cass in J. Chem. Educ. 2006, 83, 336.

Link to original paper on Berry Pseudorotation, J. Chem. Phys. 1960, 32, 933-938.

Microsoft Office document icon Berry_Pseudorotation.doc26.5 KB
Learning Goals: 
In answering these questions, a student will:
  • Visualize the intramolecular motion that results in the exchange of equatorial and axial atoms in trigonal bipyramidal molecules.
  • Explain how the Berry Pseudorotation results in a single resonance in the 19F NMR spectrum of PF5.
Equipment needs: 
Computer with a web browser that supports Jmol
Implementation Notes: 
I used to simply present the Berry Pseudorotation to students in lecture, attempting to use static molecular models and draw cartoons of the atom displacements and transition states on the board.  My hope that this interactive tool is a more effective way for students to “discover” the Berry Pseudorotation on their own; perhaps the knowledge will stick with them longer after “playing” with the Jmol animations. 
Time Required: 
15-20 minutes
Evaluation Methods: 
I would like to find a way to evaluate if this method of teaching the Berry Pseudorotation is more effective than presenting it in a more traditional lecture format.  However I am not really sure how to go about evaluating this.  If you have any suggestions, please post a comment.
Evaluation Results: 
Creative Commons License: 
Creative Commons Licence


Here is a simple updated version that uses JSmol


Check out this  2019 Organometallics paper on iron pentacarbonyl and Berry pseudorotations: 

Structure and Dynamics of Iron Pentacarbonyl

Peter PortiusMichael BühlMichael W. GeorgeFriedrich-Wilhelm Grevels, and James J. Turner
Organometallics Article ASAP

DOI: 10.1021/acs.organomet.9b00559

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