2. Coordination chemistry and ligand fields

2.1 Ligand field concepts

A coordination complex is a structure consisting of one or more metal cations surrounded or bound by charged (anions) or neutral (Lewis bases) organic ligands. In a first view of the crystal field, the electron density carried by the ligands affects the orbitals of the metal cations. This lifts the degeneracy of their d-orbitals, and their energy distribution depends on the geometry of the complex. A more complete picture of this coordination bond is provided by ligand field theory. Interactions between the molecular orbitals of the ligands and the atomic d-orbitals of the cations give rise to a molecular orbital diagram for the complex. This description is used to determine the binding, non-binding or anti-binding nature of these molecular orbitals....