Students were evaluated by the instructor during the activity. The instructor was available throughout the activity to answer questions and guide inquiry. This activity generated good discussion among students and most were able to work their way through.
All students completed the activity during the class period and gained a deeper appreciation for metals in biology, protein structure, and using NMR to determine protein structure. Some students needed more guiding through the rationales of metal toxicities and the multi-dimensional NMR experiments than others.
This activity was designed as an in-class group activity, in which students begin by using basic principles to predict relative toxicities and roles of metals in biological systems. Students then learn about the structures of metallothioneins using information from the protein data bank (PDB) and 113Cd NMR data. By the end of the activity, students will have analyzed data to identify and determine bonding models and coordination sites for multiple cadmium centers in metallothioneins. It is based on recent literature, but does not require students to have read the papers before class.
Students will be able to:
- Use fundamental principles to predict toxicities of metals
- Apply hard-soft acid-base (HSAB) theory to metals in biological systems
- Utilize the protein data bank (PDB) to investigate protein-metal interactions
- Explain the roles of metallothioneins in biological systems
- Evaluate 1-D and 2-D 113Cd NMR to determine structures of Cd bonding sites in metallothioneins
- Explain how NMR can be utilized to determine protein structure
This activity was developed for a Master's level bioinorganic course, but could be utilized in an advanced undergraduate inorganic course. Students were given the worksheet at the beginning of class and worked together in groups to answer the questions. Students did not have access to the paper and had not read any articles previously. Using the PDB was done as a separate in-class activity, so students had some familiarity with the PDB codes and amino acid sequences.
A brief refresher of [1H-1H] COSY was presented before beginning the activity.
A brief introduction to agostic interactions and their importance to common organometallic mechanisms such as beta-hydride elimination. Examples of compounds containing these interactions are discussed and compared to familiar molecules such as diborane. Ways to characterize these interactions are also introduced.
Slides are based on the PNAS review Agostic Interactions in Transition Metal Compounds
Brookheart, Green, and Parkin Proc. Natl. Acad.Sci. 2007, 104(7), 6908-6914
Define an agostic interaction and relate it to other types of bonding.
Provide examples of how the presence of an agostic interaction can be determined experimentally and through computational methods.
This LO was developed at the VIPEr 2017 workshop at Franklin and Marshall College so it has not yet been implemented. The authors believed that implementation of this LO is best for an inorganic course that is post-organic, post-spectroscopy. It could be helpful after a discussion of 3-center 2-electron bonding and/or Lewis acidity/basicity. A literature discussion on an interesting agostic interaction with silicon was developed in conjunction with this LO and would be appropriate after discussing this five slides about LO.
Students could be evaluated based on their participation in the in-class discussion or on their submitted written answers to assigned questions.
This LO has not been used in a class at this point. Evaluation results will be uploaded as it is used (by Spring 2018 at the latest).
This paper describes the synthesis of a stable compound of sodium and helium at very high pressures. The paper uses computational methods to predict likely compounds with helium, then describe a synthetic protocol to make the thermodynamically favored Na2He compound. The compound has a fluorite structure and is an electride with the delocalization of 2e- into the structure.
This paper would be appropriate after discussion of solid state structures and band theory.
The questions are divided into categories and have a wide range of levels.
Dong, X.; Oganov, A. R.; Goncharov, A. F.; Stavrou, E.; Lobanov, S.; Saleh, G.; Qian, G.-R.; Zhu, Q.; Gatti, C.; Deringer, V. L.; et al. A stable compound of helium and sodium at high pressure. Nature Chemistry 2017, 9 (5), 440–445 DOI: 10.1038/nchem.2716.
After reading and discussing this paper, students will be able to
- Describe the solid state structure of a novel compound using their knowledge of unit cells and ionic crystals
- Apply band theory to a specific material
- Describe how XRD is used to determine solid state structure
- Describe the bonding in an electride structure
- Apply periodic trends to compare/explain reactivity
The questions are divided into categories (comprehensive questions, atomic and molecular properties, solid state structure, electronic structure and other topics) that may or may not be appropriate for your class. To cover all of the questions, you will probably need at least two class periods. Adapt the assignment as you see fit.
CrystalMaker software can be used to visualize the compound. ICE model kits can also be used to build the compound using the template for a Heusler alloy.
The question document attempted by students in preparation for the literature discussion will be due prior to the in-class discussion. In particular, students' performance on the particle-in-a-box question will be evaluated to assess retention from the previously covered course material. The next exam following the discussion will contain specific question(s) (data/figure analysis) addressing these topics. Students' performance difference between the two will be evaluated. The extent to which students improve their post-discussion understanding of the concepts will direct future implementation.
To be determined. This is a newly proposed literature discussion.
This literature article covers a range of topics introduced in a sophomore level course (confinement/particle-in-a-box, spectroscopy, kinetics, mechanism) and would serve as a an end-of-course integrated activity, or as a review activity in an upper level course. The authors of the article employ UV-vis absorption spectroscopy of CdSe quantum dots as a tool to probe the growth mechanism of the nanoparticles, contrasting two pathways.
Reference: DOI 10.1021/ja3079576 J. Am. Chem. Soc. 2012, 134, 17298-17305
Apply the particle in a box model to interpret absorbance spectra with respect to nanoparticle size.
Analyze the step-growth and living chain-growth mechanisms proposed in this paper.
Evaluate the kinetics as it applies to the step-addition.
Sophomore level implementation: Recommend focusing on select portions (e.g. Figures 1b, 2, 5 with corresponding text) of the paper rather than having students read the entire document. The learning objects focus on select topics, such as particle-in-a-box, reaction mechanism, and kinetics in conjunction with absorbance spectroscopy. This would be a good literature discussion resource for an end-of-course integrative experience that encompasses multiple topics from general chemistry and inorganic chemistry.
Advance level implementation: For an upper division course, incorporate the paper in its entirety early in the course as an assessment on students’ ability to integrate multiple concepts that they should have learned in general chemistry, organic chemistry, and physical chemistry. To enhance the experience, accompanying the literature discussion on this paper with a laboratory experience by repeating the experimental and characterization procedures presented in the paper, and having students' compare their results with published results. This also serves to enhance students’ scientific literacy by critically assessing the quality of the paper.
Excerpts of the paper and questions can be used on a graded event, or as lesson preparation for in class discussion.
This was developed after the semester in which I teach this material. I look forward to using it next fall and I hope to post some evaluation data at that point.
This literature discussion is based on a paper describing the ligand-based reductive elimination of a diphosphine from a thorium compound (Organometallics, 2017, ASAP). The thorium compound contains two bidentate NHC ligands providing an opportunity to discuss the coordination of these ligands. The ligand-based reduction is very subtle and would be challenging for students to pick up without some guidance. The compound undergoing reductive elimination also presents an excellent introduction into magnetic nonequivalence and virtual coupling. In addition, the compounds presented in this paper provide the opportunity to do electron counting on f-block compounds.
Upon completing this LO students should be able to
- Use the CBC method to count electrons in the thorium compounds in this paper
- Describe the bonding interaction between a metal and a NHC ligand
- Discuss magnetic nonequivalency and virtual coupling
- Describe ligand-based reductive elimination and rationalize how it occurs in this system
Evaluation was conducted by the instructor walking around the classroom and addressing individual problems students had.
From classroom observations, most students were able to properly count electrons and oxidation states for the metals in the complexes and rationalize the ligand coordination modes. Here, the main source of confusion was how to account for the Z-type Co-Zr interaction. The MO diagrams generated the most discussion and were the most difficult part for students (as was expected). The reactivity was also initially conceptually difficult for students, but once they realized how to treat the M-M bonded system, students were able to apply fundamental organometallic reactions to the system. Many students forgot what they had learned about magnetic moments in the previous quarter, but figured it out and were excited to apply knowledge from the previous course.
This problem set was designed to be an in-class activity for students to practice applying their knowledge of metal-metal bonding (as discussed in the previous lecture) to recently published complexes in the literature. In this activity, complexes from four papers by Christine M. Thomas and coworkers are examined to give students practice in electron counting (CBC method), drawing molecular orbitals, and fundamental organometallic reactions.
Following the activity, a student should be able to:
· Determine electron counts and oxidation states of complexes with M-M bonds using CBC electron counting method
· Draw molecular orbital diagrams for M-M bonds
· Determine M-M bond order
· Propose mechanisms for reactions at M-M centers
· Apply fundamental inorganic chemistry to reports in the literature
This was implemented in the second quarter of advanced inorganic chemistry (4th year level) before the second midterm as an in-class group activity. The worksheet generated a lot of interest from the students and generated good discussions in a class of 23 students. In the previous lecture, we discussed basic metal-metal bonding, including drawing MO diagrams and determining bond order for homobimetallic complexes. This worksheet was a reasonable extension, requiring students to apply this knowledge to more complicated systems.
I just stumbled on this site while refreshing myself on the use of Slater's rules for calculating Zeff for electrons. There are a variety of calculators on there including some for visualizing lattice planes and diffraction, equilibrium, pH and pKa, equation balancing, Born-Landé, radioactive decay, wavelengths, electronegativities, Curie Law, solution preparation crystal field stabilization energy, and more.
I checked and it calculated Zeff correctly but I can't vouch for the accuracy of any of the other calculators.
This is not a good teaching website but would be good for double checking math
I used this to double check my Slater's rules calculations (and found a mistake in my answer key!)