Reactivity of reduced nitroprusside, [Fe(CN)5NO .]3-, toward oxygen
In the reaction of [Fe(CN)5NO•]3- with O2 (4:1 stoichiometry), the nitroprusside ion [Fe(CN)5NO]2- (NP) was quantitatively produced. The rate law was -1/4d[Fe(CN)5NO•3-]/dt = k2[Fe(CN)5NO•3-][O2], with k2 = (3.5 ± 0.2) × 105 M-1 s-1 at 25.0 °C. The rate was insensitive to pH (range 9-11) and ionic s...
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2007
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00027863_v129_n2_p278_Videla http://hdl.handle.net/20.500.12110/paper_00027863_v129_n2_p278_Videla |
| Aporte de: |
| Sumario: | In the reaction of [Fe(CN)5NO•]3- with O2 (4:1 stoichiometry), the nitroprusside ion [Fe(CN)5NO]2- (NP) was quantitatively produced. The rate law was -1/4d[Fe(CN)5NO•3-]/dt = k2[Fe(CN)5NO•3-][O2], with k2 = (3.5 ± 0.2) × 105 M-1 s-1 at 25.0 °C. The rate was insensitive to pH (range 9-11) and ionic strength (I = 0.1-1 M). Excess cyanide was used for minimizing the production of [Fe(CN)4NO]2-, which appeared to be much less reactive. Addition of O2 to the NO• group is proposed to generate peroxynitrite bound to Fe(III), which reacts rapidly with [Fe(CN)5NO•]3- to yield [Fe(CN)5NO2•]3-. Reaction between the latter radical ions leads to the final product, NP. Comparison with the autoxidation rates for other NO• complexes reveals that the rate constants decrease with an increase in ENO+/NO, the redox potentials of the bound NO+/NO• couples. Six-coordination appears to be necessary for attaining reasonable electrophilic rates for the NO• ligand, as with other heme and non-heme complexes. Copyright © 2006 American Chemical Society. |
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