Fluxional Bonds in Tubular Molecular Rotors B3-[Ta@B18] and B4-[Ta@B18]+ in 18-Electron Configurations

Abstract

Boron and metal-doped boron nanoclusters possess unique fluxional behaviors in dynamics. Detailed bonding analyses performed in this work indicate that, similar to the experimentally observed B2-[Ta@B18]− (1), the theoretically predicted tubular molecular rotors B3-[Ta@B18] (2) and B4-[Ta@B18]+ (3) possess typical fluxional 4c–2e and 3c–2e σ-bonds atop the Ta-centered [Ta@B18] double-ring tube between the Bn unit (n = 3, 4) and upper B9 ring, unveiling the fluxional bonding nature of the Bn-[Ta@B18]q complex series (n = 2–4, q = n − 3) which follow the 18-electron rule in different charge states. Chiral conversions via pseudo-rotations are observed in the fluxional processes between the Bn unit (n = 3, 4) and Ta-centered [Ta@B18] double-ring tube.