Smallest Möbius Aromatic Metallaborocycle and MB2: B-B Bond Strengthening Versus Weakening

Abstract

Dewar–Chatt–Duncanson (DCD) model has been the celebrated model in describing metal–ligand donation and backdonation. However, this runs counter in the case of M-diborene and M-diboron complexes with early transition metals where B-B bond strengthening has been observed. However, the present study reveals that with late transition metals, the usual DCD model is preserved and the weakening of B-B bond in MB2 complexes (M = Ni, Pd, Pt) is observed. Electronic structure analysis has rationalized the opposite bonding scenario. Interestingly, all these MB2 (M = late transition metals) species are found to possess Möbius aromaticity while the early transition metal MB2 complexes are Hückel aromatic.