A Uranium(II) Arene Complex That Acts as a Uranium(I) Synthon.

Two-electron reduction of the amidate-supported U(III) mono(arene) complex U(TDA) () with KC yields the anionic bis(arene) complex [K[2.2.2]cryptand][U(TDA)] () (TDA = -(2,6-di-isopropylphenyl)pivalamido). EPR spectroscopy, magnetic susceptibility measurements, and calculations using DFT as well as multireference CASSCF methods all provide strong evidence that the electronic structure of is best represented as a 5f U(II) metal center bound to a monoreduced arene ligand. Reactivity studies show reacts as a U(I) synthon by behaving as a two-electron reductant toward I to form the dinuclear U(III)-U(III) triiodide species [K[2.2.2]cryptand][(UI(TDA))(μ-I)] () and as a three-electron reductant toward cycloheptatriene (CHT) to form the U(IV) complex [K[2.2.2]cryptand][U(η-CH)(TDA)(THF)] (). The reaction of with cyclooctatetraene (COT) generates a mixture of the U(III) anion [K[2.2.2]cryptand][U(TDA)] () and U(COT), while the addition of COT to complex instead yields the dinuclear U(IV)-U(IV) inverse sandwich complex U(TDA) (). Two-electron reduction of the homoleptic Th(IV) amidate complex Th(TDA) () with KC gives the mono(arene) complex [K[2.2.2]cryptand][Th(TDA)(THF)] (). The C-C bond lengths and torsion angles in the bound arene of suggest a direduced arene bound to a Th(IV) metal center; this conclusion is supported by DFT calculations.