New features on the redox chemistry of metal nitrosyls {(M-NO+; M-NO; M-NO-/HNO)}.

RONCAROLI, F.; VIDELA, M.; SLEP, L. D.; OLABE, J. A.

COORDINATION CHEMISTRY REVIEWS

Elsevier

Año: 2007 vol. 251 p. 1903 - 1930

0010-8545

Abstract             We describe new developments in the coordination chemistry of bound nitrosyl, considering its three formal redox states: NO+, NO• and NO-/HNO. We emphasize on the correlation between well disclosed structural and spectroscopic aspects and different reactivity properties associated with the total electron content, according to the {MNO}n description (n = 6, 7, 8 for the above mentioned nitrosyls, respectively). The selected systems contain mainly 6-coordinated nitrosyl-complexes with different MLx fragments (M = Fe, Ru, Os; L = cyanides, polypyridines, amines, EDTA, porphyrins, etc). We focus heavily on the pentacyanonitrosylferrate systems, though with an eye toward a generalized description. For the NO+-complexes (n = 6), the electrophilic reactivity toward selected nucleophiles: OH-, N2H4, NO2– and cysteine is analyzed. We provide a mechanistic analysis, including DFT calculations for describing the reactants, transition states, intermediates and products. The crucial role of the redox potential associated to the NO+/NO• couples, ENO+/NO, in determining the electrophilic addition reactivities is highlighted. We employ a similar approach for studying the nucleophilic reactivity of NO•-complexes (n = 7) toward O2, a reaction that has great biological significance. Finally, some recent results covering structural, spectroscopic and reactivity aspects of NO– and HNO-complexes (n = 8) are reviewed.