Organometallic chemistry

6 Apr 2020

Migratory Insertion Guided inquiry

Submitted by Adam R. Johnson, Harvey Mudd College
Evaluation Methods: 

I look to see if students are able to 

1) determine the correct number of IR stretches for the compounds,

2) calculate the labeled IR stretches from the unlabeled ones,

3) correctly predict the product distributions expected for the 3 mechanistic pathways

4) understand/explain the importance of experiment 2, negative evidence, and microscopic reversibility

Evaluation Results: 

Awaiting assessment data at time of submission; will add ASAP.

based on 3 complete submissions (43% response rate, due to COVID)

students generally had no problems with questions 1 and 2, and were able to determine the number/symmetry of IR stretches using group theory, and to predict a vibrational frequency from a areduced mass calculation.

question 3 gave them a lot of trouble. I would normally do this as an in-class exercise and be able to talk them thorugh problems. students were able to draw some of the correct products for the various mechanisms but did not understand the fact that there would be a statistical distribution of products based on the 13C label. However, I spoke with all 3 students and they said that after priming their brains with the exercise, the reading in the textbook made a lot of sense and they understood what they had missed. Perfect!

Students did not generally understand the concept of negative evidence as hoped.

For future years, if I were unable to do this exercise in class, I would want to provide more guidance to get students to think about product distribution. However, if done in class, I think that watching them struggle a bit before helping them over the hurdle would be good.

Description: 

The migratory insertion reaction is one of the "four" main reactions in organometallic chemistry. It involves the formation of an acyl group by insertion of a CO molecule into a metal alkyl bond. The reaction is sometimes called the carbonyl insertion reaction because the product appears to be a result of direct insertion of the CO into the metal alkyl, but that name implies a mechanistic pathway that may not be in operation.

The reaction of methyl pentacarbonyl manganese(I), MeMn(CO)5, was studied extensively by Calderazzo in the mid 1960s. The use of C13 labeled CO and IR spectroscopy allowed for the identification of the mechanism for the reaction among the likely possibilities of direct insertion, alkyl migration, or carbonyl migration. This guided inquiry exercise presents some of the data from the Calderazzo paper and has students interpret it to determine the mechanism of the reaction in this system.

It should be noted that there are examples of all three mechanisms operating in different chemical systems, so this exercise is specific to the manganese substrate, though it is usually more generally applied.

Learning Goals: 

Students will interpret and analyze IR data of metal carbonyls

Students will calculate IR bands for 13C labeled peaks in the IR

Students will predict product distributions for the three likely mechanisms (direct insertion, carbonyl migration, alkyl migration).

Students will compare expected and observed product distributions and identify the mechanism operating

Students will discover and discuss the concept of "negative evidence."

Equipment needs: 

none

Prerequisites: 
Corequisites: 
Subdiscipline: 
Course Level: 
Implementation Notes: 

In my course, we usually cover isotopic labeling and its application to IR spectroscopy. We also use group theoretical methods to predict and assign M-CO stretches the correct symmetry labels and whether they are IR active or not. These two factors could be removed from the guided inquiry and presented as additional data to the students if you don't cover these topics. The rest of the activity is self contained. Access to the paper is not required, as the IR bands are in the document but a reference is provided.

Time Required: 
30-50 minutes
26 Mar 2020
Evaluation Methods: 

Student learning is assessed by answers to simple scenario based questions accompanying this resouce.

Description: 

One of the features of the laboratory associated with my Inorganic chemistry course is learning to do some air sensitive chemistry using Schlenk lines (and sometimes gloveboxes).  Of course, COVID19 is keeping us out of the lab this year!  This is a collection of short web based resources (text and video) detailing begining use of a Schlenk line, something about drying and degassing solvents, and transferring liquids to a reaction flask.  It is accompanied by questions I am having students answer as part of the alternate lab I am creating in place of our usual organometallic lab experiemnt.  If you have a favorite resource that might be better/supplement the ones I found, please add to the comments!

Prerequisites: 
Corequisites: 
Course Level: 
Learning Goals: 

A student will be able to explain the basic operation of a Shlenk line and how to add reagents and solvents to a flask under inert atmosphere.

Time Required: 
2 hours, if all videos are watched and resources read.
21 Mar 2020

chromium and molybdenum arene complexes (COVID-19 version)

Submitted by Adam R. Johnson, Harvey Mudd College
Evaluation Methods: 

i have no idea.... yet! (growth mindset!)

Evaluation Results: 

I will report this later this spring.

Description: 

The synthesis of (arene)Cr(CO)3 and (arene)Mo(CO)3 complexes are fairly standard experiments in the organometallic curriculum. I present here some student data and experimental descriptions of real procedures carried out at Harvey Mudd College over the previous two to three years. The word document has the answers in it so it is posted under "faculty resources" but the raw data (pdf or png form) is presented for those who need data to support their distance learning classrooms in the Spring of 2020. I also include an input file for Mo(benzene)(CO)3 should you desire to use WebMO or Gaussian to carry out some calculations. 

 

there was a minor mistake in the reported integrations for one of the complexes in the original faculty only file; it has been fixed in the v2 version.

Course Level: 
Prerequisites: 
Corequisites: 
Learning Goals: 

Students will interpret provided data to write their own experimental sections for molecules they were unable to prepare in the lab. The guided inquiry part allows students to use data to predict the outcome of a chemical reaction.

Equipment needs: 

be able to view PDF/PNG files

Implementation Notes: 

I have not used this yet but will be using it spring 2020.

Time Required: 
unknown
21 Mar 2020

Ferrocene acylation - The Covid-19 Version

Submitted by Chip Nataro, Lafayette College
Description: 

This is the classic Chromatography of Ferrocene Derivatives experiment from "Synthesis and Technique in Inorganic Chemistry" 3rd Ed. (1986 pp 157-168) by R. J. Angelici. There are no significant changes from the experiment published in the book so details will not be provided. What is provided are links to some excellent videos showing the experiment and characterization data for students to work with. For the time being this will be a living document. Currently it has 1H, 13C{1H}, COSY, DEPT, HMBC, HSQC IR, UV-Vis, GC-MS and Cyclic Voltammetry raw data files for all compounds for students to work with. It also includes processed 1H, 13C{1H}, COSY, DEPT, HMBC, HSQC, IR, GC-MS and Cyclic Voltammetry data for all compounds. If anyone has any additional means of characterization they would like to include (say Mossbauer) please feel free to contact the author.

Corequisites: 
Learning Goals: 

A student should get an appreciation for what doing this lab would be like by watching videos. In addition, the student will analyze the data provided and learn about the characterization of ferrocene, acetylferrocene and 1,1'-diacetylferrocene.

Equipment needs: 

Nothing.

The NMR data comes from a Bruker instrument and can be opened with TopSpin, MestReNova and perhaps other programs.

Implementation Notes: 

Like most everyone at this time this is going to be a trial by fire.

20 Mar 2020

setting up an air-sensitive reaction (video)

Submitted by Adam R. Johnson, Harvey Mudd College
Evaluation Methods: 

have not done

Evaluation Results: 

n/a

Description: 

This is a video I made to demonstrate the basics of air-sensitive reaction setup under nitrogen flush. It is the simplest, most basic method for setting up a reaction with air/water sensitive reagents.

The link goes to my channel on YouTube.

Corequisites: 
Subdiscipline: 
Learning Goals: 

After watching this video, a student will be able to set up a reaction under nitrogen. Or, if there is a global pandemic and the students are at home, they will at least see how it is done.

Course Level: 
Implementation Notes: 

I made this and am sharing it with my students because they did not get an opportunity to set up an air sensitive reaction this year.

Time Required: 
5 minutes to watch video
20 Mar 2020

virtual inorganic lab experiments with data

Submitted by Adam R. Johnson, Harvey Mudd College

This collection includes new and/or updated lab experiments useful for online/distance learning. To be included in this collection, data should be provided for others to use in their new virtual laboratory courses. This collection was prepared as part of my response to the COVID-19 pandemic.

Prerequisites: 
Corequisites: 
Course Level: 
19 Mar 2020

Online Seminar Talks

Submitted by Amanda Reig, Ursinus College
Evaluation Methods: 

Student summaries are simply graded as complete/incomplete and are checked to see that they did in fact watch the video. If student summaries are felt to be lacking substance or incomplete, we will indicate areas they can improve on future summary reports.

Description: 

In an attempt to find a substitute for our chemistry seminar program, I have found a number of YouTube videos of chemists giving seminar lectures, mostly between 2017-2020. The topics span a range of chemistry disciplines, and are all around 1 hour in length (typical seminar length).  I have not watched them, so I cannot vouch for video quality. Feel free to add additional links in the comments below if you know of or find any great talks.

We will ask students to select and watch a certain number of lectures from the list and then write and submit a one-page summary of the talk.

Prerequisites: 
Course Level: 
Learning Goals: 

A student should be able to summarize the key points of a lecture presented by a seminar speaker.

Corequisites: 
Time Required: 
1 hour
25 Jul 2019

1FLO: One Figure Learning Objects

Submitted by Chip Nataro, Lafayette College
Corequisites: 

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