Nucleophilic Addition Reactions of the Nitroprusside Ion – The Case of O‐Methylhydroxylamine

Abstract

The kinetics of the reaction between aqueous solutions of [Fe(CN)5NO]2– and NH2OCH3 has been studied by means of UV/Vis spectroscopy and complementary solution techniques, FTIR/ATR spectroscopy, mass spectrometry, and isotopic labeling ([Fe(CN)515NO]2–), in the pH range 6.0–9.3, I = 1 M (NaCl). The main products were nitrous oxide (N15NO), CH3OH, and [FeII(CN)5H2O]3–, characterized as the [FeII(CN)5(pyCONH2)]3– complex (pyCONH2 = isonicotinamide). In excess NH2OCH3, the kinetic runs indicated pseudo‐first‐order behavior, with corresponding rate constants, kobs [s–1], that correlated linearly with the concentration of NH2OCH3. The rate law is: R = kexp[Fe(CN)5NO2–][NH2OCH3], with kexp = (4.1 ± 0.4) × 10–4 M–1 s–1 at 25 ± 0.2 °C, ΔH# = 27 ± 1 kJ mol–1, and ΔS# = –220 ± 5 J K–1 mol–1, at pH 7.1. The value of kexp is much lower than that for similar addition reactions of NH2OH and of the N‐substituted methyl derivative. In addition, the latter reactions exhibit a third‐order rate law with a linear dependence of R on the concentration of OH–. The reaction profile has been modeled by density functional theoretical methodologies, providing mechanistic evidence on the different reaction steps, namely, the adduct formation and subsequent decomposition processes, with valuable comparisons with the reactivity of other nucleophiles with [Fe(CN)5NO]2–.

New perspectives on the reactions of metal nitrosyls with thiolates as nucleophiles

“…These studies were extended for a diverse class of bases that includes N-(ammines, hydrazine, hydroxylamine, and azide) [4][5][6][7][8] and S-binding species (hydrogen sulfide, sulfites, and thiols). Table 3 summarizes some constants calculated in the reaction of metal nitrosyls with thiols and OH − nucleophiles (see Section 2.3) [4,[7][8][9][10][11][12][13][14][15][16].…”

“…(1) with different nucleophiles were treated in a similar manner for many years, subsequent studies performed with several techniques described multiple and complex steps following the simple addition shown in Eq. (1) [5,6,10,11]. Recently, these reactions have received additional interest due to the biological implications of some species, such as hydroxylamine, H 2 S/HS − , cysteine, and glutathione [17][18][19][20].…”

Reatividade de acetatos trinucleares de rutênio com ligantes nitrito e óxido nítrico em meio aquoso

“…Além da presença de água, há a presença de outras espécies que podem reagir com os complexos, gerando espécies que interferem nos resultados observados. No caso, diversas espécies como NH2R, NH2OH, N2H4, OH -, HS -, e tiolatos podem encadear reações de ataque nucleofílico à molécula de NO + (DÓZSA; KORMOS; BECK, 1984;GUTIÉRREZ et al, 2002;GUTIÉRREZ;OLABE;AMOREBIETA, 2012;OLABE et al, 1984;REED;ROPER, 1972).…”