Synthesis and Catalytic Activity of Water-Soluble Ruthenium(II) Complexes Bearing a Naphthyridine–Carboxylate Ligand

The synthesis of water-soluble (η6-arene)­ruthenium­(II) complexes based on pyrazolyl–naphthyridine ligands modified with a carboxylate group is reported. The complexes are easily accessible in good yields via complexation of [(arene)­RuCl2]2 with 7-pyrazolyl-1,8-naphthyridine-2-carboxylic acid (1). All complexes have been characterized by spectroscopic and elemental analyses. The complexes {[Ru­(η6-arene)­(N,N′-1)­Cl]­Cl} (arene = benzene (5), p-cymene (6)) were further confirmed by X-ray diffraction studies. These complexes are soluble in water (ca. 10 mg/mL) and are catalytically active in hydrogen-transfer reduction of carbonyl compounds in aqueous medium with the use of HCOOH/HCOONa as the hydrogen source.