Cluster-Geometry-Associated Metal-Metal Bonding in Trimetallic Carbide Clusterfullerenes

Geometry configurations of the metallic clusters play a significant role in the involved bonding nature. Herein, we report the crystallographic characterization of unprecedented erbium-based trimetallic clusterfullerenes, namely, Er3C2@I-h(7)-C-80, in which the inner Er3C2 cluster presents a lifted bat ray configuration with the C2 unit elevated by similar to 1.62 angstrom above the Er-3 plane. Within the plane, the Er center dot center dot center dot Er distances for Er1 center dot center dot center dot Er2, Er1 center dot center dot center dot Er2A, and Er2 center dot center dot center dot Er2A are 3.4051( 15), 3.4051(15), and 3.3178(15) angstrom, respectively, falling into the range of the metal-metal bonding. Density functional theory calculations unveil the three-center-one-electron Er-Er-Er bond in Er3C2@I-h(7)-C-80 with one electron shared by three metals, and thus, its exceptional electronic structure can be expressed as (Er-3)(8+)(C-2)(2-)@C-80(6-). Interestingly, with the further observation on the geometry configurations of the encapsulated clusters in M3C2@C-2n (M = Sc, Y, and Lu) series, we find that the lifted bat ray configuration of the inner cluster is explicitly associated with the formation of the bonding interactions between the inner metals. This finding provides insights into the nature of metal-metal bonding and gives guidelines for the design of the single-molecule magnet.

Automated summary

In this study, the crystallographic characterization of unprecedented erbium-based trimetallic clusterfullerenes was reported, revealing their exceptional electronic structure. The lifted bat ray configuration of the inner cluster was found to be associated with the bonding interactions between the inner metals, providing insights into the nature of metal-metal bonding.