Ligand nature of coordinated NO2− in the oxidation reaction of Ru(II) complexes, [Ru(NO2)(OH2)(py)4−2n(bpy)n]+(n=0, 1, 2), and their related complexes

Abstract Under the chemical conditions using NaClO, the title complexes undergo an oxidation which gives different products: [Ru IV (ONO)(O)(py) 4 ] + (for n =0), [Ru IV (NO 2 )(O)(py) 2 (bpy)] + (for n =1) and [Ru 2 III,III O(NO 2 ) 2 (bpy) 4 ] 2+ (for n =2). All these complexes retain the original nitro nitrogen. However, the electrochemical oxidation proceeds along basically the same mechanistic pathway; each of the title complexes undergoes a one-electron oxidation to give the corresponding Ru(III) complexes; then the formation of a dimeric intermediate consisting of both nitro and nitrito complexes of Ru(III) results in the generation of a nitrosyl complex of Ru(II). This pathway suggests that a metal-nitrite bond breaking process is involved in the electrochemical oxidation. We also investigated the oxidation of the μ-oxo complex of Ru(III,III) with nitro ligand, [Ru 2 O(NO 2 ) 2 (bpy) 4 ] 2+ , which was isolated as the product species in the chemical oxidation of the complex with n =2. In this oxidation, an intramolecular electron transfer process is operating; a one-electron oxidized (NO 2 − Ru III ORu IV NO 2 − ) 3+ moiety first changes to (NO 2 − Ru III ORu III NO 2 0 ) 3+ ; this change brings about the liberation of the non-charged NO 2 , along with the formation of solvation species containing the (NO 2 − Ru III ORu III CH 3 CN) 3+ moiety.