Inverse Bonding – Backbonding: Metal to Ligand σ and Ligand to Metal π Dative Interactions between Bismuth and Boron

There are many types of coordinating bond types, but an inverse bonding-backbonding (IBBB) with a metal to ligand σ donation and a ligand to metal π backdonation (a “σZ-πL” interaction) is unheard of. Herein we computationally describe one such case based on a borabenzene ligand and a bismuth pincer complex. We believe that IBBB involving d orbitals in transition metals is impossible, but a π charge transfer to a post-transition metal empty p orbital can do the trick.