Computational Study of Intramolecular Arene Palladation at a Palladium(IV) Center

A computational study of the palladation of a pendant phenyl group in the Pd-IV complex PdCl2(CF3)(biH)(Bu(2)(t)bpy) to form PdCl(CF3)(bi)(Bu(2)(t)bpy) (bi = biphenylenediyl) indicates that this reaction occurs via an SEAr mechanism after dissociation of a chloride ion from the Pd center. Chloride dissociation occurs trans to the Pd-C(biH) bond. This dissociation is followed by rate-limiting isomerization of the square-pyramidal five-coordinate cation to place the remaining chloride ligand trans to the pendant phenyl group, with concomitant formation of a Pd-arenonium species. The free chloride ion then assists the departure of the Cipso proton from the arenonium complex as HCl. Key findings of this study include the occurrence of facile ligand dissociation and isomerization at this PdIVcenter as well as the participation of a classical SEAr mechanistic pathway in this transformation.