Cationic (η1-Allyl)-palladium Complexes as Feasible Intermediates in Catalyzed Reactions

Abstract

A computational study on the structure and reactivity of (η1-allyl)-Pd complexes has been performed on model systems containing different neutral and cyclometalating ligands. A comparison of the reactivity of these compounds with the usually proposed (η3-allyl)-Pd derivatives has been performed to investigate the feasibility of the participation of the former as intermediates in Pd-catalyzed reactions. These complexes are more stable than (η3-allyl)-Pd derivatives with a cyclometalated PCP tridentate ligand. Intermediates, transition states, and activation and reaction energies have been calculated for several reactions of cationic and neutral complexes: (a) nucleophilic attack of NH3 on the allyl system, (b) nucleophilic attack of the γ-allyl carbon on formaldehyde, (c) pallada-ene reactions of σ-allyl complexes with ethylene, and (d) pallada-ene type reactions of σ-allyl complexes with acetylene. Our results show that (η1-allyl)-Pd complexes are probably not involved as intermediates in the Tsuji−Trost...