Theoretical description of metal–ligand bonding within f-element complexes: A successful and necessary interplay between theory and experiment

Abstract

The quantum chemical study presented here shows various aspects of the bonding of lanthanide (La 3+ , Gd 3+ ) and actinide (U 3+ , Am 3+ , Cm 3+ ) ions with N -heterocyclic ligands (polyazines, BTP: bis(1,2,4-triazinyl)-2,6-pyridine). Several families of complexes, differing by their coordination sphere, have been examined. Clearly, the lanthanide complexes always show a purely ionic bonding. The behaviour of U(III) is also well defined with a more or less strong backbonding interaction whatever the complex is. In contrast, the heavy actinides (Am 3+ and Cm 3+ ) are changeable, with a weak covalent character, going from donation to backdonation, depending on the coordination sphere of the complex.