Nature of the interaction between β-substituents and the allyl moiety in (η3-allyl)palladium complexes

Abstract

β-Substituted (η3-allyl)palladium complexes are key-intermediates in synthetically important highly selective palladium-catalyzed transformations. Recently, several studies have appeared on the investigation of the electronic interactions occurring between β-substituents and the allyl moiety in these complexes. The nature of these electronic interactions was explored by MP2 and DFT calculations, and it has been studied by X-ray crystallography, kinetic experiments and stoichiometric nucleophilic substitution of the β-substituted (η3-allyl)palladium complexes. These studies revealed a new type of σ–π electronic interaction between the β-substituents (Cl, OR, OAc and SiR3) and the allyl–metal moiety. It was found that these electronic interactions influence: (i) the structure of (η3-allyl)palladium complexes; (ii) the kinetic and thermodynamic stability of these species; and (iii) the regiochemistry of the nucleophilic attack on the allyl moiety.