Synthesis and catalytic activity of ruthenium(II) complexes containing pyridine-based tridentate triamines () and pyridine carboxylate ligands ()

The reaction of [(p-cymene)RuCl2]2 with K[ NO ⌢ a - b ] ( NO ⌢ - = 2-picolinate, a or 2-quinaldinate, b) gave neutral [(p-cymene)RuCl( NO ⌢ a - b )] (1a–b), complexes which were treated with pyridine-based meridional triamine ligands ( ′ NNN ⌢ ⌢ ′ ) to create complexes of the type [RuCl( NO ⌢ a - b )( ′ NNN ⌢ ⌢ ′ )] (2a: ′N = Nd, NO ⌢ a - = 2-picolinato; 2b: ′N = Nd, NO ⌢ b - = 2-quinaldinato; 3a: ′N = Nb, NO ⌢ a - = 2-picolinato; 3b: ′N = Nb, NO ⌢ b - = 2-quinaldinato; 4a: ′N = Np, NO ⌢ a - = 2-picolinato; 4b: ′N = Np, NO ⌢ b - = 2-quinaldinato). The new compounds were characterized by elemental analysis, IR and NMR spectroscopy and, 1b was studied by single crystal X-ray diffraction. The complexes 1–4 have been employed as catalysts for the transfer hydrogenation (TH) of acetophenone derivatives to secondary alcohols in the presence of KOH using 2-propanol as a hydrogen source at 82 °C. The highest catalytic activity was obtained with 3a.