The metal-metal (M-M) bonding in dimetallofullerenes presents the peculiar electronic structures as well as the chemical and physical properties.^[1-2] For Y and medium-size lanthanides (Gd, Tb, Dy), computations by Shinohara et al. showed that M₂@C₈₀ has one unpaired electron occupying the M–M bonding molecular orbitals, and the other electron is delocalized over the carbon cage (Figure 1a).^[3] Such molecules are unstable radicals. Recently, we have succeeded in the capture of the elusive M₂@C₈₀ (M=Y, Dy) as benzyl derivatives (Figure 1b). The structure was unambiguously determined (Figure 1c, d).^[4] In this contribution, the synthesis, separation, and structural characterizations of the elusive M₂@C₈₀ will be presented and discussed.

[1] A. A. Popov, S. Yang, L. Dunsch, Chem. Rev. 2013, 113, 5989-6113.

[2] A. A. Popov, S. M. Avdoshenko, A. M. Pendas, L. Dunsch, Chem. Commun. 2012, 48, 8031-8050.

[3] Z. Wang, R. Kitaura, H. Shinohara, J. Phys. Chem. C 2014, 118, 13953-13958.

[4] F. Liu, D. S. Krylov, L. Spree, S. M. Avdoshenko, N. A. Samoylova, M. Rosenkranz, A. Kostanyan, T. Greber, A. U. B. Wolter, B. Büchner, A. A. Popov, Nat. Commun. 2017, 8, 16098.