Stabilizing a three-center single-electron metal-metal bond in a fullerene cage

Trimetallic carbide clusterfullerenes (TCCFs) encapsulating a quinary M 3 C 2 cluster represent a special family of endohedral fullerenes with an open-shell electronic configuration. Herein, a novel TCCF based on a medium-sized rare earth metal, dysprosium (Dy), is synthesized for the first time. The molecular structure of Dy 3 C 2 @ I h (7)-C 80 determined by single crystal X-ray diffraction shows that the encapsulated Dy 3 C 2 cluster adopts a bat ray configuration, in which the acetylide unit C 2 is elevated above the Dy 3 plane by ∼1.66 Å, while Dy-Dy distances are ∼3.4 Å. DFT computational analysis of the electronic structure reveals that the endohedral cluster has an unusual formal charge distribution of (Dy 3 ) 8+ (C 2 ) 2− @C 80 6− and features an unprecedented three-center single-electron Dy-Dy-Dy bond, which has never been reported for lanthanide compounds. Moreover, this electronic structure is different from that of the analogous Sc 3 C 2 @ I h (7)-C 80 with a (Sc 3 ) 9+ (C 2 ) 3− @C 80 6− charge distribution and no metal-metal bonding. A novel trimetallic carbide clusterfullerene, Dy 3 C 2 @ I h (7)-C 80 , was successfully synthesized and isolated, and the encapsulated Dy 3 C 2 cluster adopts a bat ray configuration featuring an unprecedented three-center single-electron Dy-Dy-Dy bond.