Bonding, Aromaticity, and Possible Bond-Stretch Isomerism in an “All-Metal” Cluster—[Be6Zn2]2−

Aromaticity is one of the most fascinating concepts toward understanding conceptual chemistry. Since its inception,1 this unique idea of aromaticity was by and large a property monopolized chiey by the organic chemists where benzene and later on a galaxy of its derivatives and other similar ring compounds were studied. However, this concept was further extended in leaps and bounds into the diverse elds of inorganic and cluster chemistry where similar properties were exhibited by borazines, boranes, fullerenes, and metallocenes. The seminal idea of “all-metal” aromaticity invoked by Boldyrev et al.2 in an all-aluminum [Al4]2− system added a new dimension to chemical thinking. The Al4

2− system exhibits π-aromaticity over a σ-framework. Since then the idea of “all-metal” aromaticity has made a deep impact in understanding the structure, bonding, and reactivity trends of a plethora of metal clusters.3-19 The stability of metal clusters primarily rest upon the formation of a strong metal-metal (M-M) bond. Such an example with the Zn-atom was rst reported by Resa et al.20