Reductive Eliminations from Diarylpalladium(II) Complexes: A Combined Experimental and Computational Investigation.

Abstract

The diverse mechanisms for the reductive elimination of biaryl compounds from diarylpalladium(II) complexes with a tetradentate ligand were investigated through a combined experimental and computational study. At least four distinct chemical triggers with specific regioselectivity exist for this elimination. Heating of the complexes in inert solvents (e.g., para-xylene) reveals their relatively high thermal stability as reflected by a very high barrier for a unimolecular reductive elimination. In contrast, electron-donor ligands like triphenylphosphine induce a facile reductive elimination via twofold associative ligand exchange as confirmed by kinetic experiments, which are in good agreement with the computational results. Oxidants, such as H2 O2 , can trigger an oxidation-induced reductive elimination via palladium(IV) intermediates at room temperature. Rearrangement of the diarylpalladium(II) complexes can occur in organic acids, facilitating a reductive elimination with distinct regiochemical outcome.