Understanding the Role of Solvents and Spin-Orbit Coupling in an Oxygen-Assisted SN 2-Type Oxidative Transmetalation Reaction.

The aerial oxidation of PdII to PdIV has emerged as an integral component of sustainable catalytic C-H functionalization processes. However, a proper understanding of the factors that control the viability of this oxidative process remains elusive. An investigation of the intricate mechanism of the transmetalation reaction of the aerial oxidative transformation of [(Me3 tacn)PdII Me2 ] (Me3 tacn=N,N',N''-trimethyl-1,4,7-triazacyclononane) to [(Me3 tacn)PdIV Me3 ]+ has been conducted by using DFT, along with multireference methods, such as second-order n-electron valence-state perturbation theory (NEVPT2) with complete active space self-consistent field theory (CASSCF). The present endeavor predicts that the thermodynamics and kinetics of the oxygen activation step are primarily dictated by the polarity of the solvents, which determine the amount of charge transfer to the oxygen molecule from the PdII center. Additionally, it is observed that the presence of a protic solvent has a significant effect on the spin-orbit coupling term at the minimum energy crossing point of the triplet and singlet surfaces. Moreover, it is shown that the intermetal ligand-transfer phenomenon is an important instance of an oxygen-assisted SN 2 reaction.