The Softer Side of Actinide Chemistry

Compared to transition metals, the chemistry of the actinides is understudied. For example, while transition metals have crystal field theory to make predictions about their structure and reactivity, no such convenience is available with the f elements. The structure and bonding of the actinides is necessary to provide insight into how to selectively separate these elements from complex matrices, for example, spent nuclear fuel, as well as our curiosity as chemists to better understand the periodic table. One of the major questions is that looms in actinide chemistry is the role of valence orbitals (6d and 5f) in actinide-ligand bonding. This is one of the grand challenges that the U.S. Department of Energy has deemed, “The f Electron Problem.” Our group has taken a unique approach to this problem. Actinides are large, radioactive, electropositive metals that need and want electron density, hence they prefer hard Lewis bases such as oxygen and nitrogen. Our group has been developing the chemistry of the actinides with soft Lewis bases, such as phosphorus and arsenic, thus depriving the metal center of electron density. This dramatically increases the reactivity of these complexes leading to unusual reactivity, which will be the focus of this seminar.