9 Jun 2008

Werner From Beyond the Grave

Literature Discussion

Submitted by Maggie Geselbracht, Reed College
This short communication in 2001 established the structure of a dinuclear cobalt complex based on a single crystal X-ray diffraction study of crystals taken from the Werner collection. The X-ray structure clarified the nature of the bridging ligands including a bridging superoxo group. As such, it offers a nice entry point into the nomenclature of bridging ligands, a discussion of O2 related ligands such as peroxide and superoxide, and the evolution of characterization techniques from Werner's time to the present.
Related activities: 
Implementation Notes: 
I first used this as a problem set question rather than an in-class activity. I spent so much time talking to groups of students during office hours to clarify the concepts that I think it would have worked much better as an in-class discussion.  If you have VIPEr Faculty Status, you will find solutions to these questions under the Problem Set activites (follow the link to related activities above).
Time Required: 
1 hour
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Creative Commons Licence


For the past three years, I've been teaching inorganic chemistry using a homework method I learned from a pchem colleague.  I assign one semi-hefty homework problem due at the beginning of each lecture.  If students don't get full credit on the first try, they can re-submit the problem a week later.  Most students have liked this approach because it keeps them working steadily.  I also give non-graded problems for each topic we cover.

I adapted this literature discussion into a daily homework problem - see attached.  One small effect of using this problem is that we can have a short conversation in class about what constitutes authorship on a scientific paper and why Werner was included as an author on the 2001 paper.

PS  I see that 2013 is the 100th anniversary of Werner's Nobel Prize in chemistry!  Maybe another inorganic chemist will win the prize this fall...

For the past couple of years, I've used this as an in-class problem instead of a homework problem.  This year I switched back to using it as a homework problem.  I agree with Maggie's assessment that it works better as an in-class problem.  It's very hard for the students to correctly translate the formula into a structure and generally understand the concepts on their own.

I thought I was being all cool this year by giving the students the .cif from the actual paper and asking them to use Mercury (free software) to measure the O-O and Co-N bond lengths and then figure out the puzzle.  It was only when I started grading the problems that I realized the error in this approach - the crystal structure shows a triply-bridged complex, so it takes the whole mystery out of the problem.  Oops.

I used this again this year, now back to an in-class problem.  It was good to check in with everyone as they worked through the sections. 

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