Easy synthesis of new chiral tridentate Schiff bases and their use as [N,N,O] ligands for Ni and Pd complexes -: Catalytic behaviour versus hydrogenation reactions

The chiral [N,N,O] tridentate unsymmetrical Schiff bases 3-5 (aryl = phenyl, 1-naphthyl, 2-naphthyl) were synthesised easily in high purity and good yields. All the organic compounds were characterised by elemental analysis, mass spectrometry, IR, H-1 and C-13 NMR spectroscopy. Palladium(II) and nickel(II) Schiff-base complexes were prepared as air-stable solids. Because the [N,N,O] ligand is tridentate after deprotonation of the -OH group, the coordination of the metal ion is completely stereospecific and gives rise to only one diastereoisomer. The X-ray crystal structures of the complexes [Ni(3)(OAc)] and [Pd(4)(OAc)] were determined. These complexes were shown to be very active catalysts (TOE up to 10(6) h-1) for the hydrogenation of olefins and imines under mild conditions. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).