F. Keene, D. Salmon, J. L. Walsh
Jul 1, 1980
Citations
1
Influential Citations
46
Citations
Journal
Inorganic Chemistry
Abstract
Nitro complexes of bis(bipyridyl)ruthenium(III) are unstable with respect to oxidation of the coordinated nitro ligand. For the complexes Ru(bpy),(L)NOz' (L = NH,, py (pyridine), pyr (pyrazine), CH3CN, PPh,) and Ru(bpy),(CI)N02, electrochemical oxidation to the ruthenium(II1) state results in production of the corresponding nitrosyl and nitrato complexes in a 1:l ratio. A two-electron oxidation of the nitro ligand to nitrate occurs, and the corresponding reduction is delocalized over two sites, one at the metal (Ru"' - Ru") and one at the ligand (RuNO' - Ru&O). For the chloro complex the rate of disappearance of Ru"'(bpy),(C1)NOz+ is first order in Ru(II1) and the rate constant, determined by monitoring the reaction by cyclic voltammetry, is 1.8 X sd in acetonitrile at room temperature. For the pyridyl complex, variable scan-rate cyclic voltammetry experiments show the intervention of an intermediate past the initial oxidation step. A mechanism is suggested for the oxidation of coordinated nitrite which consists of an initial rearrangement of the nitro ligand from N bound to 0 bound. The 0-bound isomer is a reactive intermediate which undergoes a bimolecular oxygen atom transfer reaction probably with the corresponding Ru"-N02 complex to give the observed products. The acid-base properties of the R~(bpy)~(py)NO~~-Ru(bpy)~(pya)cNidO-~ba's e pair and formal reduction potentials for the chloro and pyridyl complexes as two-electron-acceptor, oxide ion donor oxidants have been determined. In basic solutions, oxidation of the nitro group becomes catalytic and the nitrato complex is the sole product of the oxidation.