Oxidation of the ligand in nitro complexes of ruthenium(III)

Keene, F. Richard, Salmon, Dennis J., Walsh, Jerry L., Abruna, Hector D., and Meyer, Thomas J. (1980) Oxidation of the ligand in nitro complexes of ruthenium(III). Inorganic Chemistry, 19 (7). pp. 1896-1903.

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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.

Item ID: 22788
Item Type: Article (Research - C1)
ISSN: 1520-510X
Date Deposited: 29 Aug 2012 01:14
FoR Codes: 03 CHEMICAL SCIENCES > 0302 Inorganic Chemistry > 030207 Transition Metal Chemistry @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970103 Expanding Knowledge in the Chemical Sciences @ 100%
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