B Be B : A Boron-Beryllium Sandwich Complex.

Planar boron clusters have often been regarded as "π-analogous" to aromatic arenes because of their similar delocalized π-bonding. However, unlike arenes such as C H and C H , boron clusters have not previously shown the ability to form sandwich complexes. In this study, we present the first sandwich complex involving beryllium and boron, B Be B . The global minimum of this combination adopts a unique architecture having a D geometry, featuring an unprecedented monocyclic Be ring sandwiched between two quasi-planar B motifs. The thermochemical and kinetic stability of B Be B can be attributed to strong electrostatic and covalent interactions between the fragments. Chemical bonding analysis shows that B Be B can be considered as a [B ] [Be ] [B ] complex. Moreover, there is a significant electron delocalization within this cluster, supported by the local diatropic contributions of the B and Be fragments.