Ruthenium Complex Bearing Pyrrolbipyridine and Dimethyl Sulfoxide ligands: Syntheses, Structures, Substitution Reactions, and Catalysis Ammonia Oxidation Behavior

Abstract

Treatment of cis-[Ru(dmso)₄Cl₂], bipy and Hpbp (dmso = dimethyl sulfoxide, bipy = 2,2'-bipyridine, Hpbp = 6-(1H-pyrrol-2-yl)-2,2'-bipyridine) in the presence of Et₃N affords ruthenium complex [Ru(pbp)(bipy)(dmso)]·PF₆ (1). This complex shows the S→O linkage isomerization of the dmso ligand upon oxidation of Ru center from +II to +III, as confirmed by the thermodynamic and kinetic data obtained from cyclic voltammetry (CV) experiments. The photochemical S→O linkage isomerization of the dmso ligand in 1 is found. Taking advantages of the photoinduced linkage isomerization in 1, complexes [Ru(pbp)(bipy)(CH₃CN)]·PF₆ (1-CH₃CN) and [Ru(pbp)(bipy)(NH₃)]·PF₆ (1-NH₃) are synthesized with high yield via upon irradiation the DMSO ligand of 1 in the presence of CH₃CN and NH₃, respectively. These complexes are fully characterized by NMR, IR, EA, ESI-MS, EA. The X-ray diffraction analysis displays that CH₃CN and NH₃ ligand in 1-CH₃CN and 1-NH₃ in place of dmso ligand in 1 coordinate to Ru center at axial position. Complex 1-NH₃ has good electrocatalytic performance for selective oxidation of ammonia to hydrazine. The proposed mechanism is also described.