Coordination Chemistry

17 Jan 2018

Metal Tropocoronand Complexes

Submitted by Anthony L. Fernandez, Merrimack College
Evaluation Methods: 

I assess the student learning by the quality of the discussion generated by this exercise.

Evaluation Results: 

I have used this exercise several times, but I am reporting the results from the Fall 2017 semester.

Students accessed the structures, measured the bond angles using Mercury, and calculated the tau4' values without any difficulties (questions 1 and 2).

When they got to the third question, they could describe what they observed, but struggled with the language. They were very concerned about how to name the observed structures. They were not satisfied with using the terms "distorted square planar" and "distorted tetrahedral" to describe the structures. (This then led into the discussion of the tau4' values and why focusing on the names of the strucutres was limiting.)

All of my students were also able to calculate the LFSE values for the Ni(II) center in the four geometries. They asked about the spin state, but I prodded them to talk it through themselves and think back to previous discussions. They quickly realized that for some of the geometries there is no difference between the HS and LS configurations. They decided to calculate the LFSE for both configuations when they were different. Once their calculations were complete, the students determined that square planar should be the preferred geometry based upon the LFSE.

The last question is the one that threw a monkey wrench into what they thought they knew. They were surprised that a d8 metal center would adopt a tetrahedral geometry since this was contrary to what they had originally learned. I then asked about what other influences would impact the observed geometry. About half of my students said that the steric repulsion of the four donor atoms (and other atoms in the tropocoronand ligand) in a square planar arrangement was greater than that in a tetrahedral arrangement. These students were then able to make the connection to the fact that this must outweigh the LFSE value and favor the geometric transition of  the nickel center.

Description: 

This exercise looks at the metal complexes of tropocoronand ligands, which were first studied by Nakanishi, Lippard, and coworkers in the 1980s. The size of the metal binding cavity in these macrocyclic ligands can be varied by changing the number of atoms in the linker chains between the aminotroponeimine rings, similar to crown ethers. These tetradentate ligands bind a number of +2 metal centers (Cd, Co, Cu, Ni, and Zn) and the geometry of the donor atoms around the metal center changes with the number of atoms in the linker chains. This exercise focuses on the tropocoronand complexes of Ni(II) and students are asked to quantitatively describe the geometry around the metal using the tau4' geometric parameter. This then leads to a discussion of the factors that influence the geometric arrangement of ligands adopted by a metal center. This exercise is used to introduce the concept of flexible metal coordination geometries in preparation of the discussion of metal binding to biological macromolecules and the entatic effect.

Learning Goals: 

After completing this exercise, a student should be able to:

  • access structures from the CCDC using their online form,
  • measure bond angles in a crystal structure using appropriate tools,
  • calculate the tau4' value for a four-coordinate metal center,
  • calculate the ligand field stabilization energy for a complex in a number of different geometries,
  • identify the factors that influence the geometry arrangment of ligands around a metal center, and 
  • explain how the interplay of these factors favor the observed geometry. 
Equipment needs: 

Students will need to have access to the CIF files containing the structural data. These files are part of the Cambridge Structural Database and can be accessed through that if an institutional subscription has been purchased. 

Students can also access these CIF files by requesting the structures from the Cambridge Crystallographic Data Centre (CCDC). The identifiers provided in the faculty-only files can be submitted using the "Access Structures" page (https://www.ccdc.cam.ac.uk/structures/) and the associated CIF files can be viewed or downloaded. Students can then measure the bond angles in the JSmol viewer or in Mercury (which is freely available from the CCDC) after downloading the files.

The CIF files for the copper complexes were not available in the CSD, so I created those CIF files from data found in the linked article.

Subdiscipline: 
Corequisites: 
Prerequisites: 
Implementation Notes: 

I have used this activity in a two different ways.

  • In the past, I have assigned this as a homework assignment and have had students complete questions 1-4 outside of our class meeting time. They requested the structures from the CCDC or used our copy of the CSD on their own time. I then facilitated a dicussion of their answers before discussing the last question as a group in class. This approach worked well.
  • This year, I decided to use this exercise as an in-class group activity. I began class with a discussion of geometric indices using the presentation that is also available on the VIPEr site and is included in the "Related activities" section. I then broke my class up into groups of three students and had each group work through the activity. After the students completed the exercise, I then shared the calculations that I did for the zinc complexes so that they could remove the complication of the LFSE values from the discussion. I was much happier with this approach because I was able to focus the discussion a bit more and use the zinc data to reinforce the overall point of the exercise.

Note that in the original articles, the dihedral angle "between the two sets of planes defined by the nickel and two nitrogen atoms of the troponeiminate 5-membered chelate rings" was reported. I have decided to use the more current tau4' parameter in this exercise.

Time Required: 
45-60 minutes
10 Sep 2017

Inclusive Pedagogy: A Misidentified Molecule and Paper Retraction

Submitted by Sibrina Nichelle Collins, Lawrence Technological University
Evaluation Methods: 

This LO has various options for evaluation. First, a rubric should be prepared based on criteria identified by the student teams for evaluating the team posters. The students will be evaluated based on their ideas and attention to detail for their individual  reponses to the discussion questions. In addition, a 7-question survey is included in the handout for the students. Four of the questions address self-efficacy questions for chemistry majors. These questions were modified from a self-efficacy instrument developed by Baldwin et al for biology students. I have included a link to the model. We should be developing assessment tools that address science identity, sense of belonging, and self-efficacy for chemistry majors. If a student does not feel comfortable in a chemistry course, they will likely not pursue a career as a chemist.

Evaluation Results: 

Will be reported later.

Description: 

This learning object focuses on teaching students how to read and use Chemical and Engineering News for class discussions and critically evaluate the scientific literature. Recently, Chemical and Engineering News published an article about the retraction of a 15-year old paper, which had misidentified a multidentate ligand, which is central to the paper (Ritter, S.K. “Chemist Retract 15-year old paper and publish a revised version.” Chem. Eng. News, 2017, 95, (36), p6). The authors published a revised paper to the journal in 2017, with the correct structure of the ligand along with an x-ray crystal structure. This activity consists of two components, namely the students working in teams to discuss the C &E News article, retracted Inorganic Chemistry paper (DOI:10.1021/acs.inorgchem.7b01932) and the revised paper (DOI:10.1021/acs.inorgchem.7b01117) and preparing a poster for a “Gallery Walk.”

Learning Goals: 

An important learning goal for this learning object is to incorporate practices for creating an inclusive learning environment for students (inclusive pedagogy). The goals for this LO are for students to:

  • Read and use C&E News for student-led discussions
  • Critically evaluate experimental evidence published in the scientific literature
  • Apply concepts learned in previous chemistry courses
  • Gain a better understanding of the peer-review process for publication and retraction
  • Appreciate the importance of structural analysis tools such as X-ray crystallography
  • Prepare a team poster to communicate scientific ideas
Prerequisites: 
Equipment needs: 

The students will need 3M Post-IT paper and markers to prepare a poster for the "Gallery Walk."

Corequisites: 
Course Level: 
Implementation Notes: 

You will need to provide access to the Chemical and Engineering News article, and the two Inorganic Chemistry articles before class. This activity will likely take two class periods The first class period should focus on discussion of the articles and developing a rubric for evaluating the posters with the class. The second class period, the students will be allowed 30 min to prepare a poster for a "Gallery Walk."

Time Required: 
Two 50 min class periods
31 Jul 2017

Inorganic Nomenclature: Naming Coordination Compounds

Submitted by Gary L. Guillet, Armstrong State University
Evaluation Methods: 

For my course I grade this assignment as a problem set.  Upon collecting the assignment I do not exhaustively grade them.  I check them over for completness.  I tell the students when I hand it out that it is designed for them to learn and then test their own comprehension and if they are stuck they should bring issues to office hours. 

On the following exam I put two or three inorganic complex names and have the students draw the structures.  The test questions always incorporate isomerism in addition to combinations of common ligands and transition metals.

Evaluation Results: 

After completion of this assignment most students are able to draw straigthforward structures including some isomers on an exam.  They can identify common ligands from their names like water, ammonia, carbon monoxide.  They also understand the common conventions in naming including handling cis and trans isomers as well as fac and mer isomers.

In the most recent sample of ACS examinations (IN16D) 87% of my students answerd correctly on the question most directly related to this assignment, selecting the correct name of a given complex using a picture of the complex.  I do not have any comparative data from another teaching approach.

Description: 

I do not like to take a large amount of time in class to cover nomenclature of any kind though I want students to know the names of common ligands and the basic ideas of how coordination complexes are named.  Since it is a systematic topic I assign this guided inquiry worksheet.   The students complete it outside of class and can work at whatever pace they want.  If they are more familiar with the topics the can quickly complete it but if they are rusty or have not seen some of the material it gives them an easy entry point to ask questions to fill in any gaps in their knowledge.  This assignment covers determing charge on a metal in a complex with simple ligands, how to identify and name common isomers, and it is structured in a guided inquiry form. 

Learning Goals: 

Students will be able to identify and correctly name common ligands in a chemical structure or chemical name.

Students will be able to identify the charge on a metal or a ligand in a chemical structure.

Students will be able to identify common isomeric differences in a chemical structure or a chemical formula (cis, trans, fac, mer). 

Students will be able to use a chemical name to draw a chemical structure.

Equipment needs: 

None

Corequisites: 
Prerequisites: 
Topics Covered: 
Implementation Notes: 

I use this assignment to replace a lengthy lecture on the topic of nomenclature when covering coordination chemistry.  I have students complete this assignment outside of class.  I encourage them to work in pairs so students can jointly interpret the instructions and determine the patterns in naming complexes.  The assignment is constructed in a very straightforward manner and covers the basics of inorganic nomenclature.

Upon completion of the assignment I take about 15-20 minutes in class to quickly cover the main ideas of the assignment.  I field any questions that arose during the assignment and I do a few comprehension check type questions on the board. 

Time Required: 
1-2 hours
3 Jun 2017
Evaluation Methods: 

This LO was craeted at the pre-MARM 2017 ViPER workshop and has not been used in the classroom.  The authors will update the evaluation methods after it is used.

Description: 

This module offers students in an introductory chemistry or foundational inorganic course exposure to recent literature work. Students will apply their knowledge of VSEPR, acid-base theory, and thermodynamics to understand the effects of addition of ligands on the stabilities of resulting SiO2-containing complexes. Students will reference results of DFT calculations and gain a basic understanding of how DFT can be used to calculate stabilities of molecules.

 
Prerequisites: 
Corequisites: 
Course Level: 
Learning Goals: 

Students should be able to:

  1. Apply VSEPR to determine donor and acceptor orbitals of the ligands

  2. Identify lewis acids and lewis bases

  3. Elucidate energy relationships

  4. Explain how computational chemistry is beneficial to experimentalists

  5. Characterize bond strengths based on ligand donors

Implementation Notes: 

Students should have access to the paper and have read the first and second paragraphs of the paper. Students should also refer to scheme 2 and table 2.

 

This module could be either used as a homework assignment or in-class activity. This was created during the IONiC VIPEr workshop 2017 and has not yet been implemented.

 
Time Required: 
50 min
23 May 2017

Ligand based reductive elimination from a thorium compound

Submitted by Chip Nataro, Lafayette College
Evaluation Methods: 

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.

Description: 

This literature discussion is based on a paper describing the ligand-based reductive elimination of a diphosphine from a thorium compound (Organometallics2017, 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. 

Corequisites: 
Prerequisites: 
Course Level: 
Learning Goals: 

Upon completing this LO students should be able to

  1. Use the CBC method to count electrons in the thorium compounds in this paper
  2. Describe the bonding interaction between a metal and a NHC ligand
  3. Discuss magnetic nonequivalency and virtual coupling
  4. Describe ligand-based reductive elimination and rationalize how it occurs in this system
Time Required: 
50 minutes
3 Mar 2017

In-class peer review

Submitted by S. Chantal E. Stieber, Cal Poly Pomona
Evaluation Methods: 

Student participation was evaluated during the in-class portion based on the questions students asked. 

The formal peer review homework was evaluated based on completion, level of thought and thoroughness.

Evaluation Results: 

Overall, students were very interested in this topic and had not formally learned about the process before. There was a very lively discussion and a lot of questions were asked. All students received full credit for participation. 

Similarly, once students received their classmate's paper for peer review, they took the process very seriously and carefully went through the paper and answered the worksheet questions. 

I was very impressed by the high quality of the formal peer reviews that were turned in as homework. Students clearly spent a lot of time to carefully think about the paper and craft a reasonable response. Most students received full-credit. 

Description: 

This activity includes questions for students to answer to help guide them through the process of peer review. It was designed to assist students in writing peer reviews for research reports written by their classmates, but could be applied to literature articles as well.

Corequisites: 
Prerequisites: 
Learning Goals: 

A student will be able to:

-Explain how the peer-review process works

-Critically read through a research article

-Carefully review a research article

-Write a professional peer review

Implementation Notes: 

An overview of peer review was given with three powerpoint slides. Students then worked through a modified Q&A of the peer review module "Peer Review - How does it work?" posted by Michael Norris on VIPEr. This provided students with an example of real reviews, along with the resulting article revisions. 

The current worksheet was then passed out to students along with a research report written by one of their classmates (I assigned these and removed names). In class, students answered the questions on the worksheet and were able to ask questions of the editor (the instructor in this case). Following the in-class peer review, students had to write a formal peer review, which was turned in as homework. 

The peer review was a final component of a research report that students had been working on throughout the course. The final report was turned in after students had received the review comments back from their peers. The grade of the final report took into consideration whether or not students had made modifications based on comments by their peer reviewer.

 
Time Required: 
60 min
1 Mar 2017

Reactivity and Bonding of Complexes with Metal-Metal Bonds

Submitted by S. Chantal E. Stieber, Cal Poly Pomona
Evaluation Methods: 

Evaluation was conducted by the instructor walking around the classroom and addressing individual problems students had.

Evaluation Results: 

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. 

Description: 

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.

Corequisites: 
Course Level: 
Learning Goals: 

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

Implementation Notes: 

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.

Time Required: 
65 min
21 Feb 2017
Evaluation Methods: 

Graded problems students turned in.

Informal evaluation during discussion.

Evaluation Results: 

Graded assignments: mean of 84, std dev of 12, so a fairly broad range of understandings

Informal: Students really enjoyed getting to evaluate published work critically and were quite engaged in discussions, which helped to bring some of the students who didn't understand the paper as well up to speed.  After the paper, students have felt much more comfortable questioning what is stated in papers, particularly if little or no support is given.

I will definitely use this again!  Unfortunate to find a paper with several important oversights in the literature, but it is a good learning opportunity.

Description: 

This LO is a problem-set-style literature discussion that leads students through a critical analysis of an interesting but flawed paper from the recent chemical literature.  Students use the questions to help them work through the paper prior to class, providing plenty of raw material for an in-class discussion about various aspects of the work from a mechanistic organometallic perspective.  The questions help students critically analyze substrate tables, spectroscopic data, and computational results from DFT.

Corequisites: 
Course Level: 
Learning Goals: 
  • Students will be able to pull out important mechanistic information from substrate tables in an organometallic paper
  • Students will be able to use knowledge of organometallic mechanisms and organic chemistry to rationalize findings in a catalysis paper
  • Students will be able to use knowledge of spectroscopy, particularly NMR, to understand structure and bonding arguments in an organometallic paper
  • Students will critically analyze a paper and learn to feel comfortable questioning assertions by authors, including the major findings of a paper
Implementation Notes: 

I had students prepare answers to these questions ahead of class and bring the answers with them.  To add incentive, I collected them as a homework assignment (though I graded some of the harder ones fairly leniently).  The questions helped prepare them for a class discussion of the paper, which I led with a few slides containing information from the paper and some other useful tidbits (I am happy to send those to you if you like, just contact me).

Time Required: 
1-2 hours student prep (reading paper); 45 minutes in class discussion
3 Feb 2017

Six-coordinate Carbon In-class Activity

Submitted by Kyle Grice, DePaul University
Evaluation Methods: 

Dr. Grice will evaluate this LO later this year. 

Description: 

This is an in-class exercise developed based on a recent paper in Angewandte Chemie International Edition that reported a crystal structure of "six-coordinate" carbon. We normally think of carbon being four-coordinate at most, but this case has definitive evidence otherwise. However, we can use our inorganic chemistry knowledge to understand the structure and bonding of this molecule and rationalize its stability. Students do a pre-class exercise and then construct the MO of fhe molecule in class together. 

Learning Goals: 

After completion of this Learning Object, students will be able to:

-Assign point groups to organic molecules

-Analyze and discuss chemistry primary literature

-Identify the properties and charges of ligands

-Use Wade's rules to describe clusters

-Construct qualitative MO diagrams using symmetry as a guide

Prerequisites: 
Equipment needs: 

None

Corequisites: 
Course Level: 
Implementation Notes: 

Dr. Grice will be implementing this later this year. 

We have included an instructor guide file under Faculty files. 

Time Required: 
50 min
27 Jan 2017

Iron Catalysts for Lactide Polymerization

Submitted by Anthony L. Fernandez, Merrimack College
Evaluation Methods: 

This LO will be used to facilitate an in-class discussion of polymers and polymerization catalysts (in general) within the context of the article. Student responses will not be graded, but this LO will be evaluated by the quality of the discussion and how well it guides the students to the main points of the article.

Evaluation Results: 

This LO has not been used yet, but will be used in the Fall 2017 semester. Evaluation results will be posted after it has been used in class.

Description: 

This set of questions is intended to guide students through an excellent article by Jeff Byers and co-workers that describes the use of bis(imino)pyridine iron bis(alkoxide) complexes as catalysts for the polymerization of lactide. This set of questions is appropriate for a second-semester sophomore/first-semester junior level course in inorganic chemistry. The research described in the article ties together concepts of organometallic synthesis and characterization, catalysis, mechanistic studies, and polymer chemistry.

Given the recently revised ACS certification guidelines, this LO might be useful to faculty looking to incorporate polymer chemistry concepts into the inorganic curriculum.

 

Corequisites: 
Learning Goals: 

After completing this exercise, students should be able to:

  • Define basic terms used to describe polymerization reactions;

  • Differentiate between living polymerizations and other types of polymerization reactions;

  • Describe why the polymerization of lactic acid is important;

  • Explain how the bis(imino)pyridyl iron complex catalyzes the polymerization reaction;

  • Contrast characteristics of NMR spectra for paramagnetic complexes to those of typical diamagnetic complexes;

  • Explain how the evidence presented in the article supports the suggested mechanism;

  • Describe how the oxidation state of the iron center is critical for catalytic activity.

Implementation Notes: 

This set of questions is intended to help students extract important and useful material from this excellent article. About a week before class, students will be provided with the article and this set of questions so that they have sufficient time to read the article and answer the questions. When the students arrive in class on the designated day, the instructor should lead the discussion of the paper and have the students share and discuss their answers to ensure that each answer is correct and complete.

Time Required: 
1 hour or more

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