The degree of actinide 5f and 6d orbital contributions to bonding represents one of the most long-standing and important problems in f-element chemistry. However, quantitating f-orbital covalency is challenging to evaluate both experimentally and computationally. Chlorine K-edge X-ray absorption spectroscopy (XAS) allows for Cl-p and metal orbital mixing to be quantified, but spectral interpretation can be challenging. We have examined a series of hexachlorides with d0, d1 and f1 orbital occupancies using Chlorine K-edge XAS, TD-DFT and multiplet methods. TD-DFT of the d0 and f1 systems is in good agreement with experiment, but for the d1 systems, TD-DFT and multiplet theory offer slightly different explanations of spectral features. Evidence for Cl-3p and U-5f orbital mixing was confirmed by observed transitions into the 5f orbitals of [UCl6]1-. Together, these results confirm 5f- and 6d-contributions to bonding in [UCl6]1- and offer methods for interpreting bonding in transition metal and actinide systems with unpaired valence electrons.

d- and f-Orbital mixing in open-shell systems

249th National Meeting (2015)

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