Addition and redox reactivity of hydrogen sulfides (H2S/HS -) with nitroprusside: New chemistry of nitrososulfide ligands

The nitroprusside ion [Fe(CN)5NO]2- (NP) reacts with excess HS- in the pH range 8.5-12.5, in anaerobic medium ("Gmelin" reaction). The progress of the addition process of HS - into the bound NO+ ligand was monitored by stopped-flow UV/Vis/EPR and FTIR spectroscopy, mass spectrometry, and c...

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Detalles Bibliográficos
Autores principales: Quiroga, S.L., Almaraz, A.E., Amorebieta, V.T., Perissinotti, L.L., Olabe, J.A.
Formato: JOUR
Materias:
addition reaction
iron
N ligands
nitrososulfide ligands
nitrosyl
sulfur
Absorbance-time curves
Concentration ratio
FTIR spectroscopy
NO release
Nucleophilic attack
pH range
Reactive intermediate
Redox reactivity
Reversible process
Stopped flow
Theoretical calculations
Addition reactions
Chemical analysis
Cyanides
Fourier transform infrared spectroscopy
Hydraulic structures
Hydrogen
Mass spectrometry
pH
Reaction intermediates
Reaction kinetics
Sulfur
Ligands
ferrous ion
hydrogen sulfide
ligand
nitrogen oxide
nitroprusside sodium
article
chemical structure
chemistry
kinetics
oxidation reduction reaction
stereoisomerism
ultraviolet spectrophotometry
Ferrous Compounds
Hydrogen Sulfide
Hydrogen-Ion Concentration
Kinetics
Molecular Structure
Nitrogen Oxides
Nitroprusside
Oxidation-Reduction
Spectrophotometry, Ultraviolet
Stereoisomerism
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_09476539_v17_n15_p4145_Quiroga
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
Descripción
Sumario:The nitroprusside ion [Fe(CN)5NO]2- (NP) reacts with excess HS- in the pH range 8.5-12.5, in anaerobic medium ("Gmelin" reaction). The progress of the addition process of HS - into the bound NO+ ligand was monitored by stopped-flow UV/Vis/EPR and FTIR spectroscopy, mass spectrometry, and chemical analysis. Theoretical calculations were employed for the characterization of the initial adducts and reaction intermediates. The shapes of the absorbance-time curves at 535-575 nm depend on the pH and concentration ratio of the reactants, R=[HS -]/[NP]. The initial adduct [Fe(CN)5N(O)SH]3- (AH, Î max≈570 nm) forms in the course of a reversible process, with kad=190±20 M-1 s-1, k -ad=0.3±0.05 s-1. Deprotonation of AH (pK a=10.5±0.1, at 25.0 °C, I=1 M), leads to [Fe(CN) 5N(O)S]4- (A, Î max=535 nm, ε=6000±300 M-1 cm-1). [Fe(CN) 5NO].3- and HS2. 2- radicals form through the spontaneous decomposition of AH and A. The minor formation of the [Fe(CN)5NO]3- ion equilibrates with [Fe(CN)4NO]2- through cyanide labilization, and generates the "g=2.03" iron-dinitrosyl, [Fe(NO)2(SH) 2]-, which is labile toward NO release. Alternative nucleophilic attack of HS- on AH and A generates the reactive intermediates [Fe(CN)5N(OH)(SH)2]3- and [Fe(CN)5N(OH)(S)(SH)]4-, respectively, which decompose through multielectronic nitrosyl reductions, leading to NH3 and hydrogen disulfide, HS2-. N2O is also produced at pH≥11. Biological relevance relates to the role of NO, NO-, and other bound intermediates, eventually able to be released to the medium and rapidly trapped by substrates. Structure and reactivity comparisons of the new nitrososulfide ligands with free and bound nitrosothiolates are provided. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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