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, 1 H and 13 C 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 (TOF up to 10 6 h −1 ) for the hydrogenation of olefins and imines under mild conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)