Triamidoamine uranium(IV)-arsenic complexes containing one-, two- and threefold U-As bonding interactions

To further our fundamental understanding of the nature and extent of covalency in uranium-ligand bonding, and the benefits that this may have for the design of new ligands for nuclear waste separation, there is burgeoning interest in the nature of uranium complexes with soft- and multiple-bond-donor ligands. Despite this, there have so far been no examples of structurally authenticated molecular uranium-arsenic bonds under ambient conditions. Here, we report molecular uranium(IV)-arsenic complexes featuring formal single, double and triple U-As bonding interactions. Compound formulations are supported by a range of characterization techniques, and theoretical calculations suggest the presence of polarized covalent one-, two- and threefold bonding interactions between uranium and arsenic in parent arsenide [U-AsH2], terminal arsinidene [U=AsH] and arsenido [U≡AsK2] complexes, respectively. These studies inform our understanding of the bonding of actinides with soft donor ligands and may be of use in future ligand design in this area.