My Notes
Categories
In this literature discussion, students are asked to read an article describing a series of uranyl halide compounds that contain an alkali counterion that interacts with one or more of the uranium's ligand atoms. This paper stands out as a great example of the binding preferences of acids and bases, and can be explained very well using simple HSAB concepts. Also notable in this paper is the fact that the authors claim that HSAB concepts explain their results very well in the introduction, and then only bring it up again almost as an afterthought in the short discussion section at the end of the paper.
| Attachment | Size |
|---|---|
| Reading Questions (docx) | 20.27 KB |
| Literature Discussion (docx) | 20.38 KB |
| Reading Questions (pdf) | 298.8 KB |
| Literature Discussion (pdf) | 403.42 KB |
A student should be able to rank Lewis acid and bases in terms of relative hardness
A student should be able to interpret X-ray crystallographic structural data and identify structural motifs
A student should be able to explain the affinity that atoms have for one another in terms of HSAB theory
This activity is fairly straightforward, and my students needed little help working through the discussion questions. For most students, this was the first time they had seen molecules represented as thermal ellipsoids, so they had a little trouble identifying the atoms inside molecules, but everyone got it by the end of the class.
Evaluation
Students were evaluated on how completely they answered the pre-class reading questions.
In-class discussion questions were collected at the end of the class period. For these, students worked in groups of 2 or 3.
Most of the students grasped the major concepts by the end of the class, though there was a lot of initial confusion as to how to make sense of all the structural data in the paper.
The biggest hurdle students had to overcome was shifting their thinking from absolute terms (e.g., sodium is hard) to relative terms (e.g., sodium is harder than potassium). Once they did this, the rest of the activity becomes very simple.
Comments
Thanks for this LO, Gerard. We read the article in my small advanced inorganic course this week, and I adapted many of your questions for my students to complete before class.
We were all curious to learn more about uranium chemistry and what kinds of precautions need to be taken in the lab. (We noticed that the reactions seemed to be on a fairly small scale.) If anyone has experience and could chimine in with stories, we'd love to hear them.
As a group, we were a bit flummoxed by the lack of attention given to compound 1. Its synthesis and characterization weren't described in the experimental section. Later the authors say that it's isomorphic with compound 2 and some X-ray data is included in the discussion, but it generally seemed hard to find information about it.
These comments aren't meant to be a criticism of the LO - we're simply curious to learn more. I think the students found the article fairly accessible, and everyone likes crown ethers!
Thank you for this LO! I adapted it for a take home exam, and I think that my students were really able to solidfy the HSAB concepts in a real world problem. The majority of them were able to explain the HSAB of the complexes and how they related to what we had learned in class.
Thanks for the LO! I adapted it to just include the HSAB discussion in my lecture. A lot of students look up the paper later and are happy to see an f-element example in class.
Like other faculty who have used this literature discussion in class, the article does an excellent job of demonstrating the application of HSAB theory. However there is a confusing point at the end of the article regarding the trend in U-O bond lengths for compounds 1 & 2 and then compound 5 & 6. At the top of the last page of the article, there is the correct statement that more electron donating ligands should result in a longer/weaker U-O bond. However the remainder of the paragraph discusses how the Raman data supports the fact that compound 1, where the ligands are Cl, has the weaker U-O bond when compared to compound 2, where the ligands are Br. A similar argument is made for compounds 5 & 6. This argument seems incorrect based on the fact that Br is more electron donating than Cl. Furthermore, the difference in the Raman data cited is very small (3-5 cm-1) which is likely near the detection limit of the instrument. Finally, as the authors point out, the bond lengths in Table 1 is not reliable given the quality of the X-ray data so question #6 of the literature discussion, which does show the expected, correct trend in U-O bond length, should be used with caution.