Synthesis and reactivity

12 Jan 2015

Cobalt-Ammine complexes and theories of bonding in metals

Submitted by Erica Gunn, Simmons College
Evaluation Methods: 

Lab notebooks were collected and graded for all students. In addition to a condensed introduction and thorough lab procedure/observations section, students wrote a short conclusion and discussion of experimental error and answered the postlab questions. Experimental data was compared to literature and classmates' data (where possible), as well as to computational results. 

Evaluation Results: 

See instructor notes document. 

Almost all students were able to synthesize their complexes with little or no difficulty. One student heated too much during the evaporation stage and did not obtain product. Several students obtained low yields for synthesis A, likely due to formation of the cis- instead of the trans product. Reheating the solutions to a higher temperature produced the green trans isomer instead. 

Students were able to obtain UV/VIS and IR data for their complexes, and were interested to compare these experimental results with the computational spectra (Spartan was especially helpful to visualize the vibrational modes to understand how they are connected to symmetry). Our ability to interpret the IR spectra was somewhat limited due to the wavelength range for our instrument and poor preparation of the KBr pellets. We were able to identify some differences in the spectra, but the real identifying peaks fall below 400 cm-1 and were not measurable with our instrument. 

For my iteration of this lab, students also measured the rates of aquation of the three complexes synthesized. This experiment highlighted the dramatic differences in reactivity for the complexes. 

In general, students found this lab straightforward and easy to follow, and these examples served as an anchor for several class discussions (symmetry of vibrational modes, trans effect in kinetics of ligand substitution, isomerism in coordination complexes, etc.). 

Description: 

This is a two-week lab in which students synthesize and then characterize three Werner cobalt complexes using IR, UV/VIS and computer calculations using Spartan. Syntheses are based on procedures from:

Angelici, R. J. Synthesis and Technique in Inorganic Chemistry. University Science Books, 1996, pp 13-17.

Borer, L.L.; Erdman, H.W.; Norris, C.; Williams, J.; Worrell, J. Synthesis of trans-Tetraamminedichlorocobalt (III) chloride, Inorganic Syntheses, Vol 31, 1997, pp 270-271.

Slowinski, E.; Wolsey, W.; Rossi, R. Chemical Principles in the Laboratory 11th ed. Cengage Learning, 2016. 

Students were randomly assigned to synthesize one of the three Co complexes in week 1, and then worked in groups to characterize their complexes in week 2.* They were also required to compare the results for their complex with students in other groups. This latter process was partially completed in lab, and then student data was collected in a shared folder on Google Drive to allow all students access to data that they did not personally collect while writing their lab reports. 

 

* In my iteration of this lab, students also measured the kinetics of aquation of the three complexes, with and without solid state catalysts. That portion of the lab still requires optimization, and was removed for simplicity. See instructor notes for a more thorough discussion.

Corequisites: 
Prerequisites: 
Course Level: 
Learning Goals: 

Students will be introduced to models of bonding in coordination complexes using Werner's cobalt ammine complexes.

Each student will synthesize one cobalt ammine complex, and analyze the product using UV/VIS and IR spectroscopy. 

Students will also carry out computations using Spartan to predict the spectra, view the molecular orbitals, and visualize IR vibrational modes for the molecule, and will compare this data to their experimental results. 

Equipment needs: 

A list of chemicals and equipment required is given in the prep notes (assuming a class of 12 students).

Implementation Notes: 

See Instructor notes document.

Time Required: 
2 4-hour lab periods
9 Jan 2015

Ligand Effects in Pd-Catalyzed Cross Coupling

Submitted by Matt Whited, Carleton College
Evaluation Methods: 

Student groups presented answers at the front of the room and were questioned by other groups who had worked on the same problems.

Evaluation Results: 

Generally the groups did well and arrived at some form of the correct answer, though the class discussion part was quite important, as some answers were incomplete or focused on less important aspects of the mechanism.

Having students draw competing reaction pathways with likely intermediates was VERY IMPORTANT.

Description: 

This set of questions was used to promote discussion within small groups (3 to 4 students) on how changing ligand properties can have dramatic effects on the product distributions in Pd-catalyzed cross coupling reactions.  The questions are pretty difficult and not always straightforward, partly because they are derived from the primary literature and thus inherently "messy".

Prior to working through these problems, students would be expected to understand the basic steps in cross couplings such as Suzuki, Stille, Negishi, Kumada, Heck, etc.  It will really help if they have seen some examples of how changes in ligand bulk, denticity, and/or electron richness can favor one reaction pathway over another.

NOTE: These could be used equally easily as problem set or exam questions!

Learning Goals: 

* Students should be able to recognize that catalytic chemical reactions often have many possible competitive pathways and come up with hypotheses about relevant mechanisms for a given set of reactions.

* Students should understand the effects that ligand properties (denticity, electron richness, steric bulk) have on cross coupling reactions and make predictions based on this understanding.

Corequisites: 
Subdiscipline: 
Course Level: 
Implementation Notes: 

This activity was for an upper-level undergraduate organometallic chemistry class with about 20 students.

As mentioned above, I split students up into groups of 3 or 4.  These questions sparked some nice discussions and really helped drive home some of the kinetics I was hoping for them to learn.  I had groups volunteer to present answers, and that worked pretty well, although in the future I may just assign groups to go up to the board to draw out answers after they have had time to work on all the problems.

I have used some of these before as problems on an exam or problem set, and they work well for that purpose, too.

Time Required: 
30 minutes
6 Jan 2015

Zeolite Synthesis

Submitted by Erica Gunn, Simmons College
Evaluation Methods: 

Lab notebooks were collected and graded for all students. In addition to a condensed introduction and thorough lab procedure/observations section, students discussed how well their x-ray data matched (or didn't match) the results of the instructor and other students in the lab. (Ideally, we would have compared to an inorganic structural database, but our campus does not subscribe to these sites, and I was unable to find a free one. If this resource were available, it would be interesting to have students assign peaks and calculate cage size based on diffraction angle.) Each student wrote a short conclusion and discussion of experimental error and answered the postlab questions. 

Description: 

This lab was part of the materials science portion of my second-year inorganic chemistry course. Students synthesize a zeolite structure and grow a chemical garden as examples of silicate chemistry.

I paired this lab with several prelab exercises that included visualizing the zeolite structure (see related activities), reading a current literature article related to an active research collaboration at the school, and writing a step-by-step procedure from the literature methods section to gain practice in planning out experiments (and to appreciate the differences between lab manul procedures and a formal methods section). For simplicity, these prelab components have been eliminated from the VIPEr version of the lab, but the experiment could easily be expanded to include prelab activities that match your own research and departmental interests.

We saved the students' zeolites and attempted to use them as catalysts for the aquation of hexammine cobalt (III) complexes in a later lab experiment, but the analysis was complicated by students using inconsistent quantities of material and by residual base from the zeolite synthesis, which affected the pH of the later reaction. Since zeolite surfaces are expected to be catalytic, this might be an interesting avenue to explore in a more advanced class or with stricter experimental controls.  

Course Level: 
Prerequisites: 
Learning Goals: 

Students will gain experience with silicate chemistry and will be introduced to the industrial applications of zeolites.

Powder x-ray diffraction will be used as an analytical tool for determining material structure. 

Corequisites: 
Equipment needs: 

See prep instructions for a full list of all chemicals and equipment required (quantities calculated for a 12-student lab, working individually). 

Implementation Notes: 

See instructor notes document. 

Time Required: 
4 hours, plus oven incubation and time to filter and run XRD (see instructor notes)
6 Jan 2015

Preparation of a Ferrofluid

Submitted by Erica Gunn, Simmons College
Evaluation Methods: 

Lab notebooks were collected and graded for all students. In addition to a condensed introduction and thorough lab procedure/observations section, students analyzed their x-ray data and submitted calculated particle sizes for their ferrofluids. They compared their measured particle size and rates of ammonia addition with the rest of the class via GoogleDrive. Each student wrote a short conclusion and discussion of experimental error and answered the postlab questions. 

Evaluation Results: 

Students calculated reasonable particle sizes based on their x-ray data (we had planned to verify their measurements by SEM, but had instrument difficulties and were unable to do so), and made clear observations of their lab procedure. Most students were very excited to play with the ferrofluids and to use a new laboratory technique (XRD) to measure their samples, and comparing their data with the class results added an extra level of interest to the experiment. 

Description: 

This lab handout and supplementary materials were developed based on a publication in the Journal of Chemical Education:

Berger, P.; Adelman, N.; Beckman, K.; Campbell, D.; Ellis, A.; Lisensky, G. Preparation and Properties of an Aqueous Ferrofluid. J. Chem. Educ. 1999, 76 (7), 943-48

Students synthesize an aqueous ferrofluid in the magnetite (spinel) structure by mixing solutions of Fe(III) and Fe(II) with ammonia. The magnetite nanoparticles are then coated with surfactant to prevent agglomeration, and students can observe spiking in their ferrofluid. This experiment is a fun way to start out the semester, as it doesn't require a lot of previous knowledge and students get very excited about watching their ferrofluids "dance" with the magnets. It also serves as a memorable example of magnetic properties that can be attributed to unpaired electron spins in a crystal structure, which leads nicely into a materials science component of an inorganic course.

Corequisites: 
Prerequisites: 
Learning Goals: 

Students will:

Practice wet lab skills, including: use of volumetric pipet, buret, vacuum trap apparatus, handling of acids and bases

Gain hands-on experience synthesizing magnetic nanoparticles

Play with a memorable example of magnetic properties determined by unpaired electrons and crystal structure

 

 

Course Level: 
Equipment needs: 

See prep instructions for a full list of all chemicals and equipment required (quantities calculated for a 12-student lab, working individually). 

Implementation Notes: 

See instructor notes document.

We had 4 hours for this lab experiment, but most students were done early. Could probably be done in a shorter period if necessary (easily in 3 hours, possibly in 2). 

Time Required: 
4 hours
5 Jan 2015

The Importance of the Trans Effect in the Synthesis of Novel Anti-Cancer Complexes

Submitted by Sheri Lense, University of Wisconsin Oshkosh
Evaluation Methods: 

A student volunteer from each group was asked to share their answer with the class.  Written answers could also be collected and graded.

Evaluation Results: 

Most students did very well in all parts of this activity, although some students initially had trouble explaining the relative trans-directing ability of the ligands.

Description: 

In this activity, students apply knowledge of the trans effect to the synthesis of planar Pt(II) complexes that contain cis-amine/ammine motifs.  These complexes are of interest as both potential novel chemotherapeutic Pt(II) complexes and as intermediates for promising chemotherapeutic drugs such as satraplatin.  The questions in this LO are based on recent research described in the paper “Improvements in the synthesis and understanding of the iodo-bridged intermediate en route to the Pt(IV) prodrug satraplatin,” by Timothy C. Johnstone and Stephen C. Lippard (Inorganica Chimica Acta, Volume 424, 1 January 2015, Pages 254–259).  Students can be given this paper either prior to class or during class.  Student then work in groups of 3-4 to determine whether the sterochemistry of the Pt(II) complexes synthesized in the paper and in previous work is predicted by the trans effect, as well as whether the bond lengths in a crystal structure of one of these Pt(II) complexes is predicted by the trans influence.

Learning Goals: 

After completing this activity, students should be able to:

  • define the trans effect and trans influence
  • explain what properties of a ligand cause it to have a strong trans effect, and be able to predict the relative trans-directing ability of ligands
  • explain how the trans effect can be utilized to develop synthetic methodologies that produce the desired isomer of a square planar complex
  • apply their knowledge of the trans effect to predict the stereochemistry of a product formed from substitution of a square planar complex
  • explain why the stereochemistry of a product formed substitution of a square-planar complex may differ from that predicted by the trans effect
  • explain the effect of the trans influence on metal-ligand bond lengths
Corequisites: 
Subdiscipline: 
Course Level: 
Equipment needs: 

None

Implementation Notes: 

This was done as an in-class activity in which students worked in groups of 3-4 to complete the assignment.  This LO could also be incorporated into a homework assignment instead.

Time Required: 
20-30 minutes
30 Oct 2014

Bio-Organic Reaction Animations (BioORA)

Submitted by Steven A. Fleming, Temple University
Evaluation Methods: 

Through interviews with faculty, focus group interviews, and student surveys, we have explored the following research questions: What are faculty perceptions of BioORA’s impact on student learning? What are student perceptions of BioORA’s impact on their own learning and understanding?

An inductive mode of analysis of qualitative data in which patterns and themes emerge let us discover the specific technical features of BioORA that the instructors and students found useful, as well as the ways in which BioORA increased student engagement and helped students with visualization skills, which both the instructors and students recognized as fundamentally difficult for novices in the fields of biology and chemistry. Additionally, analysis revealed similarities and differences between the perceptions of instructors and students. For example, the instructors emphasized BioORA’s function as a link between specific concepts or principles and the larger context of the class, as well as its function as a link between lectures and lab sections, organic chemistry and biochemistry, what students learn in class and their future work in science, and the individual steps within the reaction.

See: 

“Faculty and Student Perceptions of Student Learning and Experiences with a 3D Simulation Program” Gunersel, A. B.; Fleming, S. A.; J. Chem. Ed., 2013, 90, 988-994.

“Bio-Organic Reaction Animations (BioORA): Student Performance, Student Perceptions, and Instructor Feedback” Gunersel, A. B.; Fleming, S. A.; Biochem. Mol. Biol. Ed., 2014, 42, 190-202.

Evaluation Results: 

 

See:

“Faculty and Student Perceptions of Student Learning and Experiences with a 3D Simulation Program” Gunersel, A. B.; Fleming, S. A.; J. Chem. Ed.201390, 988-994.

“Bio-Organic Reaction Animations (BioORA): Student Performance, Student Perceptions, and Instructor Feedback” Gunersel, A. B.; Fleming, S. A.; Biochem. Mol. Biol. Ed.201442, 190-202.

Description: 

 

Bio-Organic Reaction Animations (BioORA) can be used as a teaching tool for bio-inorganic courses. BioORA illustrates large biomolecules obtained from crystal structures in the Protein Data Bank using Jmol. The student can manipulate this structure, which is shown on the right-hand side of the screen of BioORA. On the left-hand side of the screen a stripped-down view of the binding site is shown. This stripped down representation can also be manipulated and has three viewing options: ball and stick, tube, and space-filling. The software helps students visualize the three-dimensional aspects of enzyme chemistry. There are more than 25 animations and several of them have coordinating metals involved in the reaction mechanisms that are illustrated.

 

Subdiscipline: 
Prerequisites: 
Corequisites: 
Learning Goals: 

 

BioORA is a visualization program for biochemistry that will focus on molecular events.  The natural tendency has been to substitute acronyms for the biomacromolecules.  This is an understandable result in light of the size of the relevant structures.  However, we have shown that computer imaging technology is sufficiently advanced now to handle animations of the actual molecules involved in the biochemical pathways.  This type of multimedia presentation can provide students with three-dimensional representations of the biomolecules and three-dimensional animations of binding and enzyme catalyzed reactions. 

 

Our goal is to bring the molecular aspects of biochemistry to the forefront.  The chemistry for the bio-organic processes is documented and the 3D visualization software is now accessible.  There is a need for more accurate molecular representation and we are eager to provide it.  We expect that students, regardless of their major, will benefit from this teaching tool.  We hope that it will improve student appreciation of the organic chemistry that occurs in biological systems. 

Course Level: 
20 Sep 2014

Learning from UCLA

Submitted by Sheri Lense, University of Wisconsin Oshkosh
Evaluation Methods: 

I do not give students a formal grade for this activity.  While we do discuss proper technique for the handling of air-sensitive liquids in this learning object, as was mentioned in the "Pyrophorics Liquid Safety Video" L.O. by Dr. Adam R. Johnson, I still watch students very closely when they are working with air-sensitive reagents in subsequent experiments.

Description: 

This learning object is designed to spark discussion and educate students taking an inorganic chemistry course about laboratory safety.  It uses the article "Learning from UCLA" by Jyllian N. Kemsley (Chemical & Engineering News (2009), Vol. 87 Issue 31, pp. 29-31, 33-34), which describes the events that led up to the tragic death of a researcher at UCLA.  I do this learning object during the first laboratory meeting of the semester after checking the students into lab and going over the course syllabus and laboratory rules.  Students are given the article and a worksheet with discussion questions related to the article before class.  Since most students in my classes have not yet had experience with the air-sensitive techniques discussed in this article, we first do an activity called "Introduction to the Schlenk Line," which is designed to acquaint students with basic air-sensitive techniques such as syringe and cannula transfer using water and provide context for the procedures described in the article.  This activity also helps familiarize students with the Schlenk line, which they use in the next week's experiment.  After students complete the "Introduction to the Schlenk Line" activity, we have a class discussion about laboratory safety using "Learning from UCLA" and the worksheet as a jumping-off point.  Since many students go on to work in the chemical industry or in a laboratory in graduate school, I hope this activity will help remind them of the importance of laboratory safety throughout their career in addition to this class.

Prerequisites: 
Learning Goals: 

Students will be able to:

1) articulate the importance of observing safety rules and regulations in the laboratory.

2) describe correct techniques for handling air-sensitive liquids, especially pyrophoric liquids, and explain the rationale behind these techniques.

3) explain the procedures to follow if an accident in the laboratory occurs.

4) discuss laboratory and institutional policies to protect the safety of laboratory workers.

 

Corequisites: 
Equipment needs: 

Below is a list of equipment used in the "Introduction to the Schlenk Line" activity.  However, this LO could also be conducted without the equipment listed below if the "Introduction to the Schlenk Line" component is omitted.  In its place, the instructor could show a video on pyrophoric liquid safety.

two Schlenk flasks and septa per group

one syringe per group

one 12-24" needle per group

one cannula needle per group

Schlenk line set-up (I usually use one Schlenk line for every two groups of students.)

nitrogen source

vacuum

liquid nitrogen or other coolant for cold trap

 

Related activities: 
Implementation Notes: 

I do this learning object during the first laboratory meeting of the semester after checking the students into lab and going over the course syllabus and laboratory rules.  This activity could also be done without the "Introduction to the Schlenk Line" component.  In its place, the instructor could show a video on pyrophoric liquid safety.

Time Required: 
One hour for "Introduction to the Schlenk line activity" and twenty minutes for "Learning from UCLA" discussion
15 Sep 2014

Fe2GeS4 Nanocrystals for Photovoltaics

Submitted by Anne Bentley, Lewis & Clark College
Evaluation Methods: 

My student led a 20-minute class discussion of this article in the spring of 2014.  The other students in the class were asked to post two questions about the article to moodle before the class meeting, but they were not asked to complete the literature discussion questions due to assignment overload at the end of the semester.

Evaluation Results: 

The six students posted good questions about the article, some of which I have incorporated into the literature discussion. One student asked why Ge was used instead of Si.  (My guess is that Si is too prone to oxidation - it's consistent with redox potentials.)  Another student wanted to know if any articles had been published after this one describing further progress.  At least two asked how the authors could determine that the photocurrent was p-type.

Description: 

I asked the students in my junior/senior inorganic course to develop their own literature discussion learning objects and lead the rest of the class in a discussion of their article.  Student Johann Maradiaga chose this article describing the synthesis and characterization of Fe2GeS4 nanocrystals with potential applications in photovoltaic devices (Sarah J. Fredrick and Amy L. Prieto, “Solution Synthesis and Reactivity of Colloidal Fe2GeS4: A Potential Candidate for Earth Abundant, Nanostructured Photovoltaics” J. Am. Chem. Soc. 2013, 135, 18256-18259. DOI: 10.1021/ja408333y).  The article describes the synthesis in hexadecylamine/octadecene of Fe2GeS4 nanoparticles and their characterization using powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and photocurrent measurements.  Building on Johann’s original set of questions, I developed this literature discussion, which is suitable for use in inorganic chemistry courses. Many thanks to article author Sarah Fredrick for reviewing the assignment and adding some great questions.

Corequisites: 
Course Level: 
Learning Goals: 

After reading and discussing this paper, a student will be able to:

  • Understand how variable growth rates along different crystal planes result in specific shapes, and predict a resulting shape given a particular set of growth rates
  • Compare the oxidation behavior of Fe and Ge over time using XPS data
  • Describe a photocurrent measurement experiment and compare the photocurrent behavior of p-type and n-type semiconductors.
  • Explain the value of a communication as compared to a longer research article

 

Implementation Notes: 

Students do not need to be experts to understand this article, but previous exposure to solid state concepts including semiconductor electronic structure, solid state phases, nanoparticle synthesis, and capping agents will be helpful to them.  Alternatively, the article could be used to introduce these topics.

This JACS communication is fairly short and written clearly, so it could make a good first literature discussion for students without previous experience reading journal articles.

I have included a large number of possible questions in the literature assignment, but as always, users should feel free to pick and choose from the options and/or add their own.

Time Required: 
45 minutes (approximately)
12 Sep 2014

Maggie's LOs

Submitted by Chip Nataro, Lafayette College
Corequisites: 
Prerequisites: 
4 Aug 2014

A Living Syllabus for Sophomore Level Inorganic Chemistry

Submitted by Sheila Smith, University of Michigan- Dearborn
Description: 

In my sophomore level inorganic course, I have experimented with the idea of a living syllabus as a way to develop my own specific learning objectives and to help the students connect the material to the tasks that will be expected of them in assessing their learning. 

Learning Goals: 

The student will connect in class activities, lecture and discussion to the tasks that will be used to assess their learning.

Prerequisites: 
Course Level: 
Equipment needs: 

none

Corequisites: 
Implementation Notes: 

We took 2 minutes at the end of each lecture period to verbalize and record the specific learning objectives for the day.  (After this lecture, what exactly does the professor expect me to be able to DO…?)  On the few occasions when we ran over and did not get to this, we used the Course Management System (CMS) discussion feature to complete the task.  The syllabus was continually modified (added to) over the ourse of the entire semester.

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