Students work in groups to derive the ligand-field diagram for a square-pyramidal vanadium(III) oxo complex using octahedral V(III) as a starting point. The activity helps students to correlate changes in orbital energies as a function of changing ligands and geometry as well as rationalizing why certain geometries can be particularly good (or bad) for particular complexes. The activity also helps students see why oxo complexes of early metals are frequently best described as triple bonds.
- Students shoud be able to apply symmetry and group theory to understand frontier molecular orbital splittings and degeneracies
- Students will be able to use correlation to predict the ordering of frontier molecular orbitals for an unknown complex from a known starting point
- Students will be able to distinguish among σ and π effects and predict their importance in determining frontier MO structure for metal complexes
- Students will be able to rationalize the preference of metal complexes for particular geometries based on number and type of bonding ligand as well as d-electron count
I use this activity in a class where we first discuss the effect of changing geometry or ligands on the ligand field splittings for metal complexes using octahedral as a starting point. Thus, the students have already seen tetrahedral, square-planar, and trigonal bipyramidal ligand field diagrams.
Then I break up the students into groups of 3-4 to work on the activity. After about 30 minutes of work as I move among the groups to answer questions or correct misconceptions, we circle up to go over the answers, which I write out on the document camera (this part usually spills over into the next class).