2 Apr 2008

Werner's Nobel Prize Address

Literature Discussion

Submitted by Maggie Geselbracht, Reed College
Categories
Description: 
Alfred Werner's Nobel prize address in 1913 offers a unique historical view on the development of coordination chemistry from the expert. With a bit of "translation" to modern terminology, this paper is very accessible to most students. Discussion of the address provides a useful introduction to coordination complexes including structure, isomers, and ligand substitution reactions. I find it interesting to mix in results from modern characterization techniques (for example, showing crystal structures of different hydrate isomers) while talking about how Werner might have characterized these compounds given the experimental tools of his time.
Related activities: 
Implementation Notes: 
I typically use this as a first exposure to coordination chemistry in a sophomore-level inorganic chemistry course. We discuss this in conjunction with a lab experiment in which students carry out classic syntheses of cobalt Werner complexes, although we have not yet covered coordination chemistry at all in lecture.
Time Required: 
50 minutes
Evaluation
Evaluation Methods: 
Some or all of the discussion questions could be assigned for students to complete before or afterwards.
Evaluation Results: 
A guided discussion works well, particularly helping students translate historical terminology into modern language.
Creative Commons License: 
Creative Commons Licence

Comments

I have also used Werner's Nobel lecture to introduce coordination chemistry, and find that it works well.
I emphasize that the older terms primary and secondary valence correspond to oxidation state and coordination number. I used to hand out or offer a link to the text, but I usually just summarize the Werner/Jørgensen debate (chain theory vs. octahedral Co) and go through isomer counting.

I am going to begin discussing coordination chemistry tomorrow in my class and then assign the Nobel prize address as an in-class activity.

Sibrina

This was awesome.

I used this as my third class on coordination chemistry, after we've discussed naming, HSAB, and isomerism.  I think this was better because students had started to get a handle on what coordination compounds looked like and what the isomers were, so we used this history discussion as a way to review our foundation before moving on to bonding.

Before class, I had students read Werner's Nobel lecture and answer three of the questions via Moodle.  My students always answer questions before class (just-in-time teaching). 

  1.  What do you think Werner meant by "loose vs. firm" acid residues?  How you you think Werner might have distinguished these experimentally?
  2. Why did Werner think the chain theory could not be right?  What experimental observations could not be explained by the chain theory?
  3. What were the 3 choices of symmetrical structures for CN=6 and how did Werner prove his case for octahedral structures?

On the day of the class--Nobel Prize Wednesday--I told the students a (slighly romanticized) story about Alfred Werner, the young upstart, and Sophus Mads Jorgensen, the "establishment" and their back-and-forth discussion of science    My story was inspired by the way Bob Crabtree told this story when I took organometallics in graduate school.  A brief version is available in the Introduction of The Organometallic Chemistry of the Transition Metals.  I also found some useful essays in Coordination Chemistry: A Century of Progress, ACS Symposium Series 565, Ed. George B. Kauffman and benefitted from reading Constable and Housecroft's Chem Soc Rev article on Werner.  (Maybe I'll work on 5-slides-about the history of coord chem...)

After my intro to the characters, I projected the discussion questions (including the ones I asked before class) and we walked through them.  We had a great discussion that even occasionally reached that nirvana of class discussions--students responding to each other!  I think that having students read before class was important to our discussion because we were all on the same page.  Whenever we encountered a complex, we discussed its name, d-electron count, oxidation number, coordination number in order to practice.  I also asked a few philosophical questions including:

1. Should Jorgensen have given up earlier in the face of Werner's coordination theory? Would it have been better for chemistry if Jorgensen had not been so conservative in the face of a new interpretation? Students really appreciated Jorgensen's role in challenging Werner to design better experiments to support the coordination theory.  They also respected him for conceding when he did.

3. Does finding only two isomers for Ma4b2 complexes prove that complexes must be octahedral? No. There could be more isomers that we just haven't prepared, so this is "negative proof."  I also mentioned that other experiments (e.g. crystal structures) are supportive of octahedral complexes.

3. Is coordination theory right? I discuss with students that I consider our atomic theory, molecular orbital theory, and even coordination theory to be models that represent reality, revealing my own constructivist epistemology.  While coordination theory seems to work pretty well, there might be a better model.

Overall, I think my class of mostly senior students appreciated the reminder that science develops over time.  I'm still thinking about how I will evaluate the effectiveness of our discussion on their exam.  I don't want to ask students very much about chain theory, but I might ask a relevant question about finding the right number of isomers.

 

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