17 Oct 2016

Ethylene compounds of the coinage metals

Literature Discussion

Submitted by Chip Nataro, Lafayette College
Categories
Description: 

This is a literature discussion based on a short paper on ethylene compounds of the coinage metals (Dias, H. V. R.; Wu, J. Organometallics 2012, 31, 1511-1517). In this paper, analogous ethylene compounds are prepared with Cu(I), Ag(I) and Au(I). The other ligand on the coinage metal is a scorpionate tris(pyrazolyl)borate ligand. The strength of the interaction between the metal and the ethylene varies significantly with the coinage metal as seen in X-ray crystallographic and spectroscopic (1H and 13C NMR) data. A particularly interesting feature is the 1H NMR spectra of these compounds under an atmosphere of ethylene in which the coordinated ethylene can exchange rapidly with the free ethylene. 

AttachmentSize
File Literature discussion worksheet1.32 MB
Learning Goals: 

After completing this literature disussion LO students should be able to

  1. recognize and count electrons for compounds with scorpionate tris(pyrazolyl)borate ligands
  2. explain how metals interact with the orbitals of an alkene
  3. describe the impact of the interaction of a metal with ethylene in terms of structural parameters and NMR data
  4. define coalescence and recognize how the rate of ligand exchange can impact the observed NMR spectrum
Implementation Notes: 

Students should read the paper before coming to class. I think I would see if they seek out the supporting information on their own rather than specifically hinting/suggesting/telling them to pay attention to it. Not having used this in class yet, my opinion on this could change.

Time Required: 
50 minutes
Evaluation
Evaluation Methods: 

I found this paper as I was writing an exam for my Inorganic Chemistry 2 class. As I was writing the question I thought this would make a really great literature discussion LO, so here it is. I have not used it in class at this point. I hope to next year at which point I will provide a bit more feedback on it.

Evaluation Results: 

None at this time.

Creative Commons License: 
Creative Commons Licence

Comments

Minor update to include orbital pictures as part of the answer to Question 6.

I used this LO in class this fall. Based on previous experience, I decided to give the students the first six questions to work on before class and the remainder of the questions in class. It came at the perfect time in the semester as we had already talked about binding of alkenes and VT NMR. I really love the results presented in this paper and it worked great in class. I think the students got a lot out of reading it, in particular, that they can understand stuff in the literature. What they struggled with the most was the counting of the Tp ligand. I had a feeling this would be a bit of an issue. The remote negative charge and having to account for it proved to be quite difficult. I totally understand this and it served as a great point of discussion. I would say you should be prepared for a lot of students thinking Tp is an L3 type ligand, similar to an arene. 

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