In this activity, students will compare and contrast two closely related structures, [Pd(dcpf)PR3]2+ (dcpf = 1,1'-bis(dicyclohexylphosphino)ferrocene; R = Me or Ph). They will be required to obtain the cif files from the supporting information of a paper. They will then make a variety of measurments in the two stuctures. These measurements can be made using a variety of different freely available programs. Instructions are provided for Mercury 3.3 and Olex2. Finally, students will be required to provide a rationale for the differences in the two structures. Students are expected to have some knowledge of crystallography, sterics vs. electronics and the trans effect.
This material is based upon work supported by the National Science Foundation under Grant Number (1057795).
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
After performing this activity students should be able to
1) Obtain cif files from the supporting information of an ACS journal
2) Open the cif files in a program that allows them to make measurements on the structures including drawing planes and finding centroids in rings.
3) Explain disorder in crystal structures.
4) Rationalize how electronics and/or sterics impact these particular structures.
A computer with an internet connection.
The provided instructions have students search for the desired information using the ACS pubs search tools. Certainly SciFinder Scholar could be employed if access is available. I have chosen to provide directions for making measurements using Mercury 3.3 and Olex2. Certainly there are other options. Of the two, Mercury is far more user friendly which is certainly an attractive option in a classroom setting. However, Olex2 provides esd values for non-standard measurements (e.g. those involving centroids) which Mercury does not do (at least as far as I know). It might be valuable to have groups perform the measurements with different programs and then have them discuss their results. There should be little to no difference in the values, but the differences in esd's could be a valuable teaching moment.
I have not used this in class yet. I plan on introducing it for the first time in the fall. I think it will be an in class activity. It might make more sense in a lab or homework setting. I don't have a lab in my fall course, so that somewhat limits my options. Hopefully more details will be forthcoming. I certainly would appreciate any feedback from anyone that adopts some or all of this Learning Object.