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.