Insights Into the Uranium Phosphine Bonds in [UCp₃(PR₃)]: A Combined Molecular Orbital, QTAIM and EDA‐NOCV Study

Abstract A series of ten uranium(III) complexes with cyclopentadienyl and monodentate phosphine ligands [UCp 3 (PR 3 )] with R=Me, Et, n Pr, i Pr, t Bu, Ph, Cy, F and CF 3 was investigated using density functional theory calculations. The ligand dissociation energies were calculated, as well as bonding analysis of the uranium‐phosphorus bond performed, using molecular orbitals, bond orders, quantum theory of atom in molecules (QTAIM) analysis and energy decomposition analysis with natural orbitals for chemical valence (EDA‐NOCV). It was found that the bond orders correlate well with the U−P bond lengths and phosphine cone angles, indicating a large influence of phosphine sterics on the bond properties. All bonding analyses show partial covalent character of the U−P bond, which is most pronounced for PF 3 and least for P t Bu 3 . π‐Backbonding was found for the most π‐acidic phosphine ligands. No good correlation was found between the ligand dissociation energies and bond metrics.