Cooperative Metal + Ligand Oxidative Addition and σ‑Bond Metathesis: A DFT Study

A computational study of the experimentally proposed mechanism of alkyne diboration by a PDICo complex yielded two fundamental catalytic steps that undergo remarkable electronic changes (PDI = bis­(imino)­pyridine). The reactions are envisaged via DFT (density functional theory) and MCSCF (multiconfiguration self-consistent field) simulations as (i) a cooperative metal + ligand oxidative addition and (ii) a σ-bond metathesis induced ligand to metal charge transfer. Analysis of the bonding of pertinent intermediates/TSs also yielded important insight that may be illuminating with regard to the larger field of green catalysis that seeks to ennoble base metals through synergy with potentially redox noninnocent (RNI) ligands. For the present case, massive changes in electronic structure do not incur massive energetic penalties. In conjunction with previous research, one may postulate that structural and energetic “fluidity” among several electronic states of RNI-M3d along the reaction coordinate is an essential signature of redox cooperativity and thus ennoblement.