Ruthenium complex bearing pyrrolbipyridine and dimethyl sulfoxide ligands: syntheses, structures, substitution reactions, and catalytic 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 the ruthenium complex [Ru(pbp)(bipy)(dmso)]PF₆ (1). This complex demonstrates the S → O linkage isomerization of the dmso ligand upon Ru-center oxidation from +II to +III, as confirmed by thermodynamic and kinetic data obtained from cyclic voltammetry (CV) experiments. The photochemical S → O linkage isomerization of the dmso ligand in complex 1 is also observed. Taking advantage of the photoinduced linkage isomerization in complex 1, complexes [Ru(pbp)(bipy)(CH₃CN)]PF₆ (1-CH₃CN) and [Ru(pbp)(bipy)(NH₃)]PF₆ (1-NH₃) are synthesized with high yield upon irradiation of the DMSO ligand of complex 1 in the presence of CH₃CN and NH₃, respectively. These complexes are fully characterized via NMR, IR, EA, ESI-MS, and EA. X-ray diffraction analysis revealed that the CH₃CN and NH₃ ligands in 1-CH₃CN and 1-NH₃ in place of the dmso ligand in complex 1 coordinate with the Ru center at the axial position. Complex 1-NH₃ demonstrates good electrocatalytic performance for the selective oxidation of ammonia to hydrazine.