Erratum: USc2C2 and USc2NC Clusters with U-C Triple Bond Character Stabilized inside Fullerene Cages (Journal of the American Chemical Society (2023) 145: 10 (5645−5654) DOI: 10.1021/jacs.2c10231)

Analysis of the bonding in the studied endohedral metallofullerene systems necessitated some clarifications and a correction. We initially conceptualized the bonding in the USc2C2 cluster based on an assumed 4-electron transfer to the fullerene cage. Re-analysis of the calculations showed that, for the isomer of C80 that was found experimentally, the Kohn−Sham orbital energy level scheme shows three unoccupied orbitals above the highest occupied level that are close in energy, followed by a large energy gap. This suggest that up to 6 electrons may be transferred from the encapsulated cluster to the fullerene, and a 6-electron transfer is consistent with the results of the density functional calculations for the analyzed low-spin states. Transfer of 6 electrons instead of 4 goes along with the presence of a C−C bond in the endohedral cluster. In fact, the first multi-center orbital in Figure 5 in the article [bottom left] is most easily conceptualized as a relatively weak C−C bond donating electron density to uranium. This further explains why the C− C distance in the endohedral cluster is large, similar to [1.1.1] propellane, but not larger, supporting our suggestion that a free cluster (neutral or charged) might remain structurally intact. (In the free +4-charged cluster, the additional electron pair is localized in a non-bonding uranium 5f orbital.) An analogous analysis of the USc2NC system follows straightforwardly. The conclusions in the article regarding the U−C covalency generated by the delocalized bonding orbitals remain unaltered. We would like to thank Prof. W. H. Eugen Schwarz for asking penetrating questions about the bonding in the systems and for pointing out a potential similarity to the propellane C− C bond. © 2023 American Chemical Society