Evidence for single metal two electron oxidative addition and reductive elimination at uranium

Abstract

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.

Facile Dinitrogen and Dioxygen Cleavage by a Uranium(III) Complex: Cooperativity Between the Non‐Innocent Ligand and the Uranium Center

“…Complex D can then react with another O 2 molecule in a four‐electron reduction process to yield complex 4 in a highly exothermal process (−148.6 kcal mol −1 from intermediate D ). In this reaction, each U III center acts as a two‐electron reductant, which is quite unusual but has been reported by Liddle and co‐workers [67] . The driving force of the second reduction is the formation of very strong U−O bonds.…”

“…[54] Angewandte Chemie Forschungsartikel observed in the reduction of N 2 .H owever, since the formal oxidation state of uranium ions in complex 4 is + V, the implication is that the uranium centers act as atwo electrons reductant, which is rather rare. [67] Although the bis(m-oxo) bridged dinuclear uranium species was previously reported, [66] the formation of complex 4 with [U(m-O) 2 U] moiety represents the first example of controlled O 2 cleavage by aU III complex under ambient conditions.…”

Facile Dinitrogen and Dioxygen Cleavage by a Uranium(III) Complex: Cooperativity Between the Non‐Innocent Ligand and the Uranium Center

“…Research Articles observed in the reduction of N 2 .H owever, since the formal oxidation state of uranium ions in complex 4 is + V, the implication is that the uranium centers act as atwo electrons reductant, which is rather rare. [67] Although the bis(m-oxo) bridged dinuclear uranium species was previously reported, [66] the formation of complex 4 with [U(m-O) 2 U] moiety represents the first example of controlled O 2 cleavage by aU III complex under ambient conditions.…”

Uranyl dication mediated photoswitching of a calix[4]pyrrole-based metal coordination cage

“…1–5 Uranium in particular has emerged as a viable tool in the design of chemical transformations showing promise in the activation of CO, CO 2 , N 2 , alkenes, and alkanes. 1,6,7–9 A number of elegant studies have also explored the inherent photochemical activity of the uranyl dication (UO 2 2+ ), which to date has been exploited for the activation of simple alkanes, 10 water, 11 and molecular oxygen. 12…”