UNCLE: Uranium in Non-Conventional Ligand Environments

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The periodic table is composed mainly of metals, thus the investigation of metal-metal bonds is fundamental to generating step-changes in our understanding of chemical bonding, catalysis, metal surface chemistry, and magnetism. This is exemplified by the discovery of zinc-zinc and magnesium-magnesium single bonds and quadruple rhenium-rhenium and quintuple chromium-chromium bonds. Indeed, transition metal-transition metal bonds are now ubiquitous. However, uranium complexes containing covalent uranium-metal bonds are limited to a 'heavy alkyl' uranium-tin bond even though theory predicts highly novel bonding manifolds. This innovative project will build on our preliminary result of the first uranium-gallium bond to deliver a significant and rapid expansion of covalent uranium-M bonds (M = transition metal or uranium). In these complexes the metal is acting as a 'non-conventional' ligand to uranium, which is novel because uranium chemistry is dominated by more traditional carbon-, nitrogen-, oxygen-, or halide-based ligands. The new uranium-metal complexes will be subjected to detailed structural, spectroscopic and theoretical interrogations in order to comprehensively establish their stability, structure, bonding, and reactivities. This nexus of early- and late-metal chemistry will give us: i) a greater understanding of chemical bonding at the foot of the periodic table; ii) the synergic utility of cooperating hard and soft metals in small molecule activation chemistry; iii) a rapid and significant contribution to actinide chemistry, which lags behind the rest of the periodic table. Studying how uranium bonds, and how it contrasts to lanthanide elements, is key to modelling the behaviour and extraction of highly radioactive plutonium and neptunium, which are too radioactive to handle in conventional laboratories, but which are present in nuclear waste. Additionally, by bonding uranium, which may shuttle between hard and soft oxidation states, directly to transition metals which can activate carbon-hydrogen, carbon-oxygen, or hydrogen-hydrogen bonds we aim to produce synergic complexes which can elaborate industrial C1 feedstocks in selective and atom/energy efficient ways. This project is adventurous and highly likely to generate results of international significance to lanthanide and actinide chemistry.