27 Jun 2016

Inquiry-Based Introduction to Carbonyl Ligands

In-Class Activity

Submitted by Emily Sylvester, Wheeling Jesuit University

This in-class worksheet introduces students to the different ways we describe organometallic ligands – bonding, properties, spectroscopy, etc. – using carbon monoxide as an example. It is structured as an inquiry-based activity, where students work together in small groups but check in with the entire class at appropriate intervals. I plan to use this activity with my advanced inorganic students next year.

File Carbonyl Ligand Activity389.47 KB
Learning Goals: 

Students will be able to:

  • Use the MO diagram, specifically frontier orbitals, of a ligand to predict the bonding (sigma, pi, donation, acceptance) interactions in an organometallic complex.
  • Describe and draw the molecular orbital interactions of a terminal CO ligand and a symmetric μ2-CO ligand with a metal.
  • Describe and explain the σ-donating and π-accepting nature of the CO ligand.
  • Understand and apply the terms backbonding and backdonation.
  • Articulate the relationship between the M-C and C-O bond strengths in a carbonyl complex.
  • Relate the CO stretching frequencies of two or more carbonyl complexes to the strength of the metal-ligand interaction and to the electron density on the metal fragment.
  • Describe various possible binding modes of a CO ligand.
Implementation Notes: 

I haven’t used this in class yet, but I plan to implement it in my advanced inorganic course. My class size ranges from 4-12 students. Students must have learned MO theory, and we will have already discussed electron counting. I anticipate that this worksheet will require one 50-minute class period. Though students will work on the activity on their own, we will convene as a class after each section to make sure all of the groups are on the right track. I anticipate that this activity will provide a solid framework for subsequent discussions of OM ligands (hydrides, dihydrogen, pi systems).

Time Required: 
I anticipate that this worksheet will require one 50-minute class period.
Evaluation Methods: 

I will assess this activity with a problem set question and/or exam question. I generally ask students to explain/predict bonding or properties of a similar or isoelectronic ligand (CN-, N2, etc.).

Creative Commons License: 
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