Endohedral metallofullerenes (EMFs) with a composition of M₂C_2n may exist as di-EMFs, M₂@C_2n, or as carbide cluster metallofullerenes (CCMFs), M₂C₂@C_2n-2. EMFs containing such metal atoms with a small ionic radius as scandium were found to prefer the CCMF form some of which had been incorrectly assigned as di-EMFs.^[1] Lu-containing EMFs remain largely unexplored in spite that lutecium also takes small ionic radius so that . In this work, we report the single-crystal X-ray crystallographic results of a series of Lu-containing EMFs to show that all of them are di-EMFs, namely Lu₂@C_2n (2n=76-86). Theoretical results confirm the formation of direct Lu-Lu bonding between the two encapsulated metal atoms.^[2]

References：

[1] X. Lu, T. Akasaka, S. Nagase, Acc. Chem. Res. 2013, 46, 1627-1635.

[2] W. Shen, L. Bao, Y. Wu, C. Pan, S. Zhao, H. Fang, Y. Xie, P. Jin, P. Peng, F.-F. Li, X. Lu, J. Am. Chem. Soc. 2017, 139, 9979−9984.