Can Dithiolate Ligands Report Electronic Communication in Transuranium Complexes?

The actinide elements and, in particular, the transuranic elements are some of the least studied elements on the periodic table. As a consequence, there is not currently a consensus on the impact of covalency in actinide complexes. Dithiolene/dithiolate ligands provided a revolution in understanding the bonding in transition metals through the geometric differences the ligands exhibit when interacting with electron-deficient or -abundant metal centers. To test if dithiolene/dithiolate ligands can be utilized to provide an analogous understanding of transuranic element bonding, density functional theory calculations have been performed on U, Np, and Pu complexes of the formula Cp2AnS2C2H2. These calculations show that the dithiolate maintains its non-innocent redox-active nature when bonding with actinides. In stark contrast with the transition metals, the direction of electron donation is reversed; in the actinide series, the direction of electron flow in high-fold cases is from the metal center to the ligand. This suggests that the communication is between the π* system of the ligand interacting with the f orbitals of the metal center.