CC BY 4.0 UnportedZhang, X.Li, W.Feng, L.Chen, X.Hansen, A.Grimme, S.Fortier, S.Sergentu, D.-C.Duignan, T.J.Autschbach, J.Wang, S.Wang, Y.Velkos, G.Popov, A.A.Aghdassi, N.Duhm, S.Li, X.Li, J.Echegoyen, L.Schwarz, W.H.E.Chen, N.2020-07-202020-07-202018https://doi.org/10.34657/3664https://oa.tib.eu/renate/handle/123456789/5035Unsupported non-bridged uranium-carbon double bonds have long been sought after in actinide chemistry as fundamental synthetic targets in the study of actinide-ligand multiple bonding. Here we report that, utilizing I h(7)-C80 fullerenes as nanocontainers, a diuranium carbide cluster, U=C=U, has been encapsulated and stabilized in the form of UCU@I h(7)-C80. This endohedral fullerene was prepared utilizing the Krätschmer-Huffman arc discharge method, and was then co-crystallized with nickel(II) octaethylporphyrin (NiII-OEP) to produce UCU@I h(7)-C80·[NiII-OEP] as single crystals. X-ray diffraction analysis reveals a cage-stabilized, carbide-bridged, bent UCU cluster with unexpectedly short uranium-carbon distances (2.03 Å) indicative of covalent U=C double-bond character. The quantum-chemical results suggest that both U atoms in the UCU unit have formal oxidation state of +5. The structural features of UCU@I h(7)-C80 and the covalent nature of the U(f1)=C double bonds were further affirmed through various spectroscopic and theoretical analyses.enghttps://creativecommons.org/licenses/by/4.0/530carbondiuranium carbidefullereneunclassified druguraniumactinidechemical bondingchemistrydetection methodfullereneinorganic compoundligandoxidationstabilizationArticlecarbon nuclear magnetic resonancecovalent bondcrystal structureelectrochemical analysishigh temperaturelow temperaturemolecular stabilityoxidationoxidation reduction potentialphotoelectron spectroscopyphotoluminescencequantum chemistrysynthesistheoretical studyX ray diffractionArticle