Palladium(0)–olefin complexes with potentially terdentate nitrogen–sulfur ligands. The role of the chelate in the olefin exchange path

The synthesis and the reactivity of Pd(0) olefin complexes [Pd(η2-olefin)(SNS)] and [Pd(η2-olefin)(NSN)] containing potentially terdentate nitrogen–sulfur ligands were studied. The presence of a potentially coordinating atom in the environment of the metal, influences strongly the fluxional behavior in solution but not the overall reactivity with respect to olefin exchange and thermodynamic stability which is very close to that of the corresponding bidentate nitrogen–sulfur complexes. The intimate mechanism of olefin exchange also involves a path promoted by the third dangling coordinating atom which induces olefin dissociation and stabilizes the ensuing Pd(0) three-coordinated species.