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.