Organopalladium(II) Complexes Containing Carbon-Bonded Heterocycles as a Ligand

Oxidative addition reactions of 2-chloropyridine, 2,6-dichloropyridine, 2-chloropyrazine, and 2-chlorobenzothiazole with tetrakis(triphenylphosphine)palladium(0) gave [{PdCl(R)(PPh3)}2] or trans-[PdCl(R)(PPh3)2] depending on the nature of the carbon-bonded heterocycles R. They are all stable and the chloride ligand is readily replaced by other halides and pseudohalides. These novel organopalladium(II) complexes were characterized by the analytical and molecular-weight data together with IR, 1H NMR and 13C NMR spectra, and the 2-pyridyl-bridged dinuclear structure of [{PdBr(C5H4N-C2)(PPh3)}2] was previously revealed by X-ray analysis. Both of the dinuclear and mononuclear 6-chloro-2-pyridylpalladium(II) complexes catalyze the cross coupling reaction between 2,6-dichloropyridine and methylmagnesium bromide to afford 2-methyl-6-chloropyridine selectively. The mononuclear 6-chloro-2-pyridylpalladium(II) complexes react with carbon monoxide to form the acyl complexes.