4.01 | MO-Diagrams of Metal Complexes

Friday May 19th 2023 | In this online lesson, we start be discovering the 18-electron rule. We establish the geometry of metal complexes as a function on how many ligands are bound, followed by the empirical observation of the spectrochemical series that lead to different high- or low-spin complexes. Later we discover that the spectochemical series can be explain by MO-theory. First we look at an octahedral complex by establishing σ-interactions only. We realize that that the ordering of the d-orbitals is similar to that predicted by crystal field theory. When we analyze the same MO-diagram, but we now include π* interactions, we realize the the energy difference between the T2g and Eg orbitals increased resulting in low-spin complexes. Conversely, when including π-interaction, we realize that the energy difference between the T2g and Eg orbitals decreases resulting in high-spin complexes. With this knowledge in mind, we completed the MO-diagram of an octahedral complex in tetragonal field. By using a simple analogy of sequently removing one-ligand, the MO-diagram of square pyramidal and square planar metal complexes could be derived. The same technique was use to generate the MO-diagram of trigonal bipyramidal, trigonal pyramidal, and trigonal planar metal complexes.

The link to the video can be found below: