Strong-field ligands

Definition

Strong-field ligands are ligands that create a significant splitting of the d-orbitals in a metal complex, leading to low-spin configurations when possible. They typically have high ligand field strength and can greatly affect the spectroscopic and magnetic properties of coordination compounds.

5 Must Know Facts For Your Next Test

1. Strong-field ligands cause a large crystal field splitting energy ($\Delta$), which often results in low-spin complexes.
2. Common examples of strong-field ligands include CN$^-$, CO, and NH$_3$.
3. The presence of strong-field ligands can lead to diamagnetic behavior in coordination compounds due to paired electrons.
4. In an octahedral field, strong-field ligands can lead to electron pairing in the lower-energy t$_{2g}$ orbitals before filling the higher-energy e$_g$ orbitals.
5. The spectrochemical series ranks ligands based on their ability to split d-orbital energies, with strong-field ligands appearing at the high end of this series.

Review Questions

• What effect do strong-field ligands have on the spin state of a coordination complex?
• Name three common strong-field ligands and describe their impact on d-orbital splitting.
• How do strong-field ligands influence the magnetic properties of a metal complex?

Related terms

Crystal Field Theory: A model that describes the breaking of degeneracies of electronic orbital states, typically d or f orbitals, due to a static electric field produced by surrounding charge distributions (ligands).

Low-Spin Complex: A coordination compound where electrons pair up in lower-energy orbitals first due to large crystal field splitting energy ($\Delta$), usually associated with strong-field ligands.

Spectrochemical Series: An empirically derived list that ranks ligands based on their ability to split d-orbital energies in transition metal complexes from weak-field to strong-field.