Palladacyclic complexes bearing CNN-type ligands as catalysts in the Heck reaction

Abstract

Preparations of novel unsymmetrical, tridentate nitrogen ligand precursors, PhN=C(CMe2)(NPh)C=N(CH2)(2)NMe2 (1) and PhN=C(CMe2)(NPh)C=N(CH2)Py(2), are described. Treatment of 1 with 1 molar equiv. (COD)PdCl2 in the presence of NEt3 or with 1 molar equiv. Pd(OAc)(2) affords orthometallated palladium(II) complexes, [PhN=C(CMe2)-(N-eta(1)-Ph)C=N(CH2)(2)NMe2] PdX (X=Cl (3); X=OAc (4)), respectively. Compound 3 can be yielded via the reaction of 4 with an excess of LiCl in methanol. Treatment of 2 with 1 molar equiv. of (COD)PdCl2, Pd(OAc)(2) or Pd(TFA)(2) affords orthometallated palladium(II) complexes, [PhN=C(CMe2)(N-eta(1)-Ph)C=NCH2Py]PdX (X=Cl (5); X=OAc (6); X=TFA (7)), respectively. The crystal and molecular structures are reported for compounds 2, 3, 5 and 6. The application of these novel palladacyclic complexes to the Heck reaction with aryl halide substrates was examined.