Synthesis and characterization of trans-[Ru(NO)Cl(L)4](PF6)2 (L = isonicotinamide; 4-acetylpyridine) and related species

The trans-[RuCl2(L)4], trans-[Ru(NO)Cl (L)4](PF6)2 (L = isonicotinamide and 4-acetylpyridine) and trans-[Ru(NO)(OH)(py)4]Cl2 (py = pyridine) complexes have been prepared and characterized by elemental analysis, UV–visible, infrared, and 1H NMR spectroscopies, and cyclic voltammetry. The MLCT band energies of trans-[RuCl2(L)4] increase in the order 4-acpy < isn < py. The reduction potentials of trans-[RuCl2(L)4] and trans-[Ru(NO)Cl(L)4]2+ increase in the order py < isn < 4-acpy. The stretching band frequency, νNO, of the nitrosyl complexes ranges from 1913 to 1852 cm−1 indicating a nitrosonium character for the NO ligand. Due to the large π-acceptor ability of the equatorial ligands, the coordinated water is much more acidic in the water soluble trans-[Ru(NO)(H2O)(py)4]3+ than in trans-[Ru(NO)(H2O)(NH3)4]3+.