Bingel–Hirsch reaction on actinidofullerene U@<i>C</i>2v(9)-C82: Improved regioselectivity compared to lanthanide counterpart

Actinidofullerenes constitute a family of fullerenes that exhibit different metal-cage interactions, electronic structures, and properties compared to lanthanidofullerenes. In this study, we investigate the reactivity of mono-uranofullerene U@C2v(9)-C82 under the Bingel-Hirsch reaction and observe significantly higher regioselectivity, along with other differences in the reaction products, compared to La@C2v(9)-C82. Two products are obtained: a cycloadduct, which is the most abundant and has been characterized by x-ray crystallography, and a minor regioisomer that is most likely a single-bond product. Density functional theory calculations can explain the experimental structure and the formation of the two products and indicate that uranium is formally U(III) in both of them. The most abundant cycloadduct is formed under kinetic control, as found for other Bingel-Hirsch adducts, whereas the single-bond product is formed after oxidation of the anionic intermediate of the conventional Bingel-Hirsch reaction. This work is a new example of the unique reactivity and chemical properties of actinidofullerenes, which arise from their distinctive actinide-fullerene interactions.