Synthesis, characterisation, and reactivity of new mononitrosyl complexes of ruthenium containing 2-(arylazo)pyridines: examples of strongly electrophilic nitrosyls

Abstract

A high-yield synthetic route to ruthenium mononitrosyls of type [Ru(NO)(NO₂)L₂]²⁺(3)[L = 2-(arylazo)pyridine] from the dinitro precursor, [Ru(NO₂)₂L₂](2) is described. Complexes (3) were isolated as crystalline perchlorate salts. In an alkaline medium, (3) regenerates (2). The electronic spectra of complexes (2) and (3) exhibit allowed metal-to-ligand charge-transfer transitions in the visible region, 400–550 nm. The nitrosyls absorb at high wavenumbers[ν(NO)ca. 1 950 cm^–1] in the i.r. spectra. All the complexes are electroactive. Secondary oxidation of co-ordinated nitrite in (2) occurs after electrochemical metal oxidation. In the case of complexes (3), two successive one-electron reductions have been observed at relatively high positive potentials.