Uranium can perform reactions that previously no one thought possible, which could transform the way industry makes bulk chemicals, polymers, and the precursors to new drugs and plastics, according to new findings from The University of Manchester.
Writing in the journal Nature Communications, the chemists have discovered that uranium can perform reactions that used to be the preserve of transition metals such as rhodium and palladium. And because uranium sits between different types of reactivity of lanthanides and transition metals it might be able to combine the best of both to give new ways of producing materials and chemicals.
Could Uranium chemistry lead to a cure for cancer? A solution to the problem of hard plastics in our oceans? This fundamental science is possibly one of the greatest discoveries of recent years with far reaching implications.
Reversible chemistry for uranium
Reversible single-metal two-electron oxidative addition and reductive elimination are common fundamental reactions for transition metals that underpin major catalytic transformations. However, these reactions have never been observed together in the f-block because these metals exhibit irreversible one- or multi-electron oxidation or reduction reactions. Here we report that azobenzene oxidises sterically and electronically unsaturated uranium(III) complexes to afford a uranium(V)-imido complex in a reaction that satisfies all criteria of a single-metal two-electron oxidative addition. Thermolysis of this complex promotes extrusion of azobenzene, where H-/D-isotopic labelling finds no isotopomer cross-over and the non-reactivity of a nitrene-trap suggests that nitrenes are not generated and thus a reductive elimination has occurred. Though not optimally balanced in this case, this work presents evidence that classical d-block redox chemistry can be performed reversibly by f-block metals, and that uranium can thus mimic elementary transition metal reactivity, which may lead to the discovery of new f-block catalysis.
The system reported here is clearly not optimised. However, the fact our combined experimental and computational evidence suggest that it can execute oxidative addition and be coerced into reductive elimination, with a substrate with a thermolytic disruption enthalpy of 93 kcal mol−176, validates the notion that with suitable ancillary ligands uranium catalysis that exploits elementary oxidative addition and reductive elimination pathways centred on a uranium(III/V)-redox couple may well be achievable. With optimised supporting ligands that better-balance the redox couple the prospect that this could therefore form the basis of new catalytic cycles in f-block chemistry, for example the production of aniline derivatives.