Insertion of Isocyanides across the Pd−C Bond in Alkyl or Aryl Palladium(II) Complexes Bearing Mixed Nitrogen−Sulfur and Nitrogen−Phosphorus Ancillary Ligands. The Mechanism of Reaction

An exhaustive study dealing with the kinetic and mechanistic behavior of alkyl- and arylpalladium complexes bearing pyridyl−thioethers (NS−R) and quinoline−phosphines (NP) as ancillary ligands when reacting with 2,6-dimethyl isocyanide (DIC) and tosylmethyl isocyanide (TosMIC) was undertaken. In these reactions some differently substituted isocyanides insert into the palladium−carbon bond of alkyl and aryl complexes bearing mixed (NS or NP) ligands. The reactions were carried out under equimolecular conditions since such a restrictive approach allows the determination of the rate constants related to the isocyanide insertion attack. Reactions carried out under nonstoichiometric conditions were also taken into account and the reaction products characterized. Usually the formation of an inserted bis-substituted isocyanide halide derivative of palladium(II) was observed. In a particular case the formation of an imidoyl dimer was detected. The structures of the monoinserted [Pd(NSt-Bu)(C(Tol)NR²)I] (NSt-Bu = 2-(tert-butylthiomethyl)pyridine) and of the dimer [Pd(CNR²)(C(NR²)Me)Cl]₂ (R² = 2,6-Me₂C₆H₃) were reported.