14 Sep 2009

Coordination chemistry via Inorganic Chemistry ASAP

In-Class Activity

Submitted by Hilary Eppley, DePauw University
This in-class activity is a fun way to show students how to apply basic concepts of coordination chemistry to complicated systems that appear in a recent issue of Inorganic Chemistry. After quickly reviewing types of ligands (monodentate, chelating, bridging), how we assign charge to ligands and metals in complexes, and the idea of coordination number, I took my class through a number of "real world" examples from the latest ASAP edition of Inorganic Chemistry. We skipped organometallic examples for now, but were able to talk about examples where ligands were both bridging and chelating and were able to work through some non-trivial examples of how to calculate charge.  This activity is also related to a "Ligand of the Week" activity from a J. Chem Ed. article by Marion Cass from Carleton College (Cass, Marion E. J. Chem. Educ. 2004 81 1145).
Learning Goals: 
  • Students will gain appreciation for the diversity of inorganic coordination complexes in the primary literature
  • Students will identify coordination numbers of metals and binding modes of ligands
  • Students will use ligand structure to calculate the charges on ligands and metals in a complex.
Equipment needs: 

Overhead projector, Computer, web-access


Implementation Notes: 
Some of the abstract graphics are hard to read and the resolution is not great on the overhead projector, so you may have to pick and choose examples based on what the class can see. It is a good chance to talk about the way that chemists use graphics, because some authors leave out charges or things that might help someone do this analysis on their abstract graphic. This year I used this activity as a lead up to their first literature discussion as a way to convince students that they have the skills to pick apart complicated structures.
Time Required: 
15-30 minutes, depending how much class time you want to take!
Evaluation Methods: 
This is just an informal class activity to apply new concepts during class time. Formal evaluation will occur later in the form of a problem set.
Evaluation Results: 
The students found the activity interesting and were able to puzzle through relatively complicated examples as a group with occasional redirection from me.  One common mistake that they made was that they forget to remove the ligand from the metal when calculating the formal charges on the ligand atoms to determine the ligand's overall charge.  
Creative Commons License: 
Creative Commons Licence


I really like this idea.  It reminds me of something I did last year when teaching inorganic.  We were covering the 18 electron rule.  Dick Schrock came to give a lecture, so I used some of the molecules from his talk to count electrons with in class.  I found it kept me on my toes - and also showed students that we could apply what we were learning in class to what real chemists do.

Thanks, Hilary!  We did this yesterday in my inorganic class after first looking at some much easier complexes.  Inorg. Chem. ASAP is filled with great doozies.  I did some pre-class research, but it was still very much a puzzle for all of us.  It's gratifying to see that you really can build a structure from its name.

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