Simulating the effect of a triple bond to achieve the shortest main group metal-metal distance in diberyllium complexes: A computational study

The subject of metal-metal bonding interactions in molecular systems continues to attract research interest. Chromium heretofore has been the only element known to afford metal-metal distances shorter than 1.700 Å in the form of Cr-Cr multiple bonds. In this computational study, the effect of a triple bond on reducing interatomic distances is simulated through forming three non-classical bonding orbitals between two beryllium atoms, thereby realizing the remarkably short Be-Be distances (1.692-1.735 Å) in kinetically stable global minimum species [L → Be₂H₃ ← L]⁺ (L = NH₃, PH₃, and noble gases Ne-Xe). Such diberyllium complexes make promising candidates for experimental realization. In particular, the Be-Be distance of 1.692 Å in [Ne → Be₂H₃ ← Ne]⁺ represents the first example of global minimum having a main group metal-metal distance under 1.700 Å. [TEA → Be₂H₃ ← TEA]⁺, which contains the bulky triethylamine (TEA) ligands, is designed as a more promising target for synthesis and isolation in condensed states.