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^t₂bpy) to form PdCl(CF₃)(bi)(Bu^t₂bpy) (bi = biphenylenediyl) indicates that this reaction occurs via an S_EAr 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 C_ipso proton from the arenonium complex as HCl. Key findings of this study include the occurrence of facile ligand dissociation and isomerization at this Pd^IVcenter as well as the participation of a classical S_EAr mechanistic pathway in this transformation.