Synthesis and characterization of trivalent lanthanide and actinide complexes with benzamidinate ligand

The recent flourishing of research on non-aqueous actinide coordination chemistry has facilitated a deeper understanding of actinide metal-ligand interactions. In particular, studies utilizing ligands with soft donor atoms (N, S) have highlighted the subtle chemical differences between trivalent actinide (An) and lanthanide (Ln) ions. They provide not only theoretical and experimental insights but also the foundation for practical applications e.g. minor actinides separation. As part of our efforts to elucidate these differences, typically attributed to an increased covalency in the actinide compounds, we conducted research using N,N’-diisopropylbenzamidinate (iPr2BA) as a model N-donor ligand.

In this work, a series of trivalent lanthanide (La, Nd, Sm, Eu) and actinide (U, Np) tris-iPr2BA complexes [M(iPr2BA)3] were successfully synthesized and characterized in solid state to gain a comprehensive understanding of the bonding situation between f-block elements and N-donor ligands. Intensive paramagnetic NMR studies in solution have been carried out and the Bleaney method was applied to separate hyperfine shift contributions (Fermi contact and Pseudocontact contributions). Furthermore, quantum chemical calculations have been performed in order to evaluate the intramolecular bonding trends and electronic structures.

ACKNOWLEDGEMENT
This study was supported by the German Federal Ministry of Education and Research (BMBF) under the project No. 02NUK059B (f-Char).