Synthesis, Structural Characterization of Schiff Base Ligands and Their Ru-II-p-Cymene Complexes, and Catalytic Activity in the Transfer Hydrogenation of Ketones

Abstract

In this study, two new Schiff base ligands, (E)-ethyl 2-(2-hydroxybenzylideneamino)-5,5,7,7-tetramethyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate (L-1) and (E)-ethyl 2-(2-hydroxy-3-methoxybenzylideneamino)-5,5,7,7-tetramethyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate (L-2), and their corresponding RuII complexes, [(LRu)-Ru-1(p-cymene)]Cl center dot 2.5H(2)O (1) and [(LRuCl)-Ru-2(p-cymene)]1.5H(2)O (2), were synthesized. The structures of Schiff bases and their Ru-II-p-cymene complexes were elucidated using microanalysis, magnetic susceptibility, molar conductivity, H-1-NMR, C-13-NMR, FT-IR, UV-Vis, LC-MS, and thermogravimetric analysis techniques. Octahedral structures for the obtained Ru-II-p-cymene complexes were proposed. The catalytic activities of the Ru-II-p-cymene complexes obtained after the characterization processes were investigated by using acetophenone derivatives in the transfer hydrogen reactions. The product conversions obtained as a result of catalytic studies were determined using GC-MS. When 4-bromoacetophenone was used as a substrate in the transfer hydrogen reactions, catalysts 1 and 2 showed good catalytic activity of 93% and 96%. [GRAPHICS] .