What is the relationship between metal-ligand bond distances and oxidation states?

The relationship between metal-ligand bond distances and oxidation states is observed such that higher oxidation states generally lead to shorter bond distances. In transition metals, as the oxidation state increases, the ability of the metal center to attract electron density from the ligands also increases due to a greater positive charge. This stronger electrostatic attraction pulls the ligands closer to the metal ion, resulting in shorter bond lengths.

In higher oxidation states, the metal ion tends to have a stronger effective nuclear charge, increasing the polarization of the metal-ligand bond. This can also enhance the covalent character of the bond, further contributing to the reduction in bond distance.

In contrast, a lower oxidation state would result in weaker attraction between the metal and the ligands due to a reduced positive charge, leading to longer bond distances. Hence, the trend demonstrates the inverse relationship, where higher oxidation states correlate with shorter bond distances.