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

<div><p>Ru(II) complexes with the general formula [RuCl₂(<i>p</i>-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(<i>p</i>–cymene)]₂ 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°C. All complexes were active catalysts for TH of acetophenone with good yields under mild conditions (after 60 minutes, yields of up to 97%).</p>