23 May 2014

The Structure and Symmetry of Metal Tris Chelates

Web Resources and Apps

Submitted by Marion E. Cass, Carleton College
Categories
Description: 

I have provided a link to a Web Resource:  The Strucutre and Symmetry of Metal Tris Chelates which I developed several years ago with my collegue Henry Rzepa from Imperial College London (and which was posted as Web Ware on the Jourmal of Chemical Education Website and is not longer available to view there).  The Web site uses 3D images of known molecules and scripted commands to teach about the symmetry elements and operations in these molecules.  Instruction is also given on assigning absolute configurations and ligand twist conformations.  Animations of the Bailar Twist and Ray Dutt Mechanism that can racemize and/or isomerize this class of complexes are also provided based on high level computational output from isolated transition states. Since originally publishing this material in 2008, I have updated the site to use JSmol and to correct out of date links and material.

I hope this is a useful resource.  I welcome feedback and suggestions.

The original reference to this work follows:

"Visualizations to Examine the Structure and Symmetry of Metal Tris Chelates: Symmetry Operations, Chirality, and Mechanisms (Bailar Twist and Rây-Dutt) that Racemize the Delta and Lambda Isomers", Cass, M. E.; Rzepa, H. S,; Journal of Chemical Education, Vol. 85, No. 5, 2008, p. 750-751.

and here is the link to our site:

http://www.people.carleton.edu/~mcass/TrisChelates/jsmol/Index.html

Learning Goals: 

Working through these web-based materials:

  1. Students should be able to locate the C3 and possible C2 axes in chiral metal tris chelates.  
  2. Students should be able to assign the Lambda or Delta absolute configuration of a given complex.
  3. Students should be able to assign a lambda or delta ligand conformation in relevant molecules.
  4. Students should be able to describe the Bailar Twist and Rây-Dutt mechanism.
  5. Students should be able to determine if the Bailar Twist motion results in racemization and/or isomerization (facial to meridional isomerization) of a metal tris chelate molecule.
  6. Students should be able to determine if the Rây-Dutt Twist motion results in racemization and/or isomerization (facial to meridional) of a metal tris chelate molecule.
Creative Commons License: 
Creative Commons Licence

Comments

I shared this website/resource with my second semester inorganic chemistry students in Winter 2016.  I really appreciated the Jmol images that freely rotated  These were really helpful to show the propeller analogy,  

 

I assigned my students to work through the exercises on their own.  

I assessed their learning by independently ( three weeks later) asking a question on an exam.  Students had physical models for the exam, instead of the website.  

 

 

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