Metal-ligand covalency in uranium, thorium, and cerium coordination chemistry: elucidating the nature of chemical bonding in f-element complexes using phosphorus ligands

Abstract

Herein the syntheses and characterization of model actinide and lanthanide complexes bearing phosphorus-based ligands are reported. High-symmetry molecular models featuring phosphorus-based ligands are very advantageous for experimental metal-ligand covalency studies because phosphorus-31 nuclear magnetic resonance spectroscopy and phosphorus-Kβ X-ray emission spectrometry can be used to study the electronic structure and orbital interactions of metal-phosphorus bonds. Furthermore, high-symmetry models simplify spectral interpretation, and reduce the complexity of computational studies of the actinides. The quantum chemistry of the actinides is very complex because relativistic effects and spin-orbit coupling are very important influences on the electronic structures of these elements. Low-symmetry and high coordination numbers are very common in actinide coordination chemistry, which further complicates actinide computational chemistry. The creation of molecular models with high-symmetry and low coordination numbers greatly reduces the complexity of empirical electronic structure studies. Using a combination of advanced spectroscopy and advanced computational methods, details about the metal-ligand orbital interactions in actinide and lanthanide complexes can be obtained. Herein reactions of advanced f-element amide complexes with phosphorus-based compounds are reported, with the intention of creating high-symmetry, low-coordinate f-metal complexes for empirical electronic structure investigations.