Synthesis and Characterization of Ruthenium(II) Complexes Bearing Benzimidazole Ligands: For Transfer Hydrogenation Catalysis

Ru(H) complexes with the general formula [RuCl2(p-cymene)(L1-3)], K1-3, (L1-3: monodentate benzimidazole ligands), [RuCl2(L5-6)(S)], K4-7, (L5-6: tridentate benzimidazole ligands, S: Solvents [methanol or acetonitrile]), and [RuCl2(L5)(L1-2)], K8-9, were synthesized from [RuCl2(p-cymenel dimer and mono- and tridentate benzimidazole ligands. The compounds were characterized by elemental analysis, IR, UV-Vis, and NMR. The synthesized Ru(II) complexes (K1-9) were tested as catalysts for the transfer hydrogenation (TH) of acetophenone to secondary alcohols in the presence of KOH using 2-propanol as a hydrogen source at 82 degrees C. All complexes were active catalysts for TH of acetophenone with good yields under mild conditions (after 60 minutes, yields of up to 97%).