Reduction of coordinated nitrosyls. Preparation, characterization, and reduction of nitrosylpentaaquochromium(2+)

Armor, John N.; Buchbinder, M.

doi:10.1021/ic50123a021

Cited by 19 publications

(6 citation statements)

References 4 publications

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“…Solutions of [Cr aq NO] 2 + were prepared from [Cr aq ] 2 + and NO by a literature procedure, [47] and purified by ion exchange on Sephadex C-25. The concentration of [Cr aq NO] 2 + was determined spectrophotometrically (l max 449 nm, e = 121 m À1 cm À1 ).…”

Section: Methodsmentioning

confidence: 99%

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Oxidative Homolysis of a Nitrosylchromium Complex

Song

Bakač

2008

Chemistry A European J

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Metal(III)-polypyridine complexes [M(NN)(3)](3+) (M = Ru or Fe; NN = bipyridine (bpy), phenanthroline (phen), or 4,7-dimethylphenanthroline (Me(2)-phen)) oxidize the nitrosylpentaaquachromium(III) ion, [Cr(aq)NO](2+), with an overall 4:1 stoichiometry, 4 [Ru(bpy)(3)](3+) + [Cr(aq)NO](2+) + 2 H(2)O --> 4 [Ru(bpy)(3)](2+) + [Cr(aq)](3+) + NO(3)(-) + 4 H(+). The kinetics follow a mixed second-order rate law, -d[[M(NN)(3)](3+)]/dt = nk[[M(NN)(3)](3+)][[Cr(aq)NO](2+)], in which k represents the rate constant for the initial one-electron transfer step, and n = 2-4 depending on reaction conditions and relative rates of the first and subsequent steps. With [Cr(aq)NO](2+) in excess, the values of nk are 283 M(-1) s(-1) ([Ru(bpy)(3)](3+)), 7.4 ([Ru(Me(2)-phen)(3)](3+)), and 5.8 ([Fe(phen)(3)](3+)). In the proposed mechanism, the one-electron oxidation of [Cr(aq)NO](2+) releases NO, which is further oxidized to nitrite, k = 1.04x10(6) M(-1) s(-1), 6.17x10(4), and 1.12x10(4) with the three respective oxidants. Further oxidation yields the observed nitrate. The kinetics of the first step show a strong correlation with thermodynamic driving force. Parallels were drawn with oxidative homolysis of a superoxochromium(III) ion, [Cr(aq)OO](2+), to gain insight into relative oxidizability of coordinated NO and O(2), and to address the question of the "oxidation state" of coordinated NO in [Cr(aq)NO](2+).

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Section: Methodsmentioning

confidence: 99%

“…The concentration of [Cr aq NO] 2 + was determined spectrophotometrically (l max 449 nm, e = 121 m À1 cm À1 ). [47] Gaseous NO (Matheson) was purified by passage through Ascarite, sodium hydroxide and water. [48] Stock solutions of NO were prepared by bubbling the purified gas through argonsaturated 0.10 m or 1.0 m HClO 4 for 30 min.…”

Section: Methodsmentioning

confidence: 99%

Oxidative Homolysis of a Nitrosylchromium Complex

Song

Bakač

2008

Chemistry A European J

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“…Solutions of Cr aq NO 2+ were prepared from Cr aq 2+ and NO and purified by ion exchange on a column of Sephadex C-25. From the UV spectral data and the reported 27 molar absorptivities at 449 nm (ε = 121 M -1 cm -1 ) and 238 nm (ε = 1170 M -1 cm -1 ), we obtained the molar absorptivity at the irradiation wavelength, ε 266 = 700 M -1 cm -1 .…”

Section: Methodsmentioning

confidence: 99%

Reaction of a Superoxochromium(III) Ion with Nitrogen Monoxide: Kinetics and Mechanism

2001

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The kinetics of the rapid reaction between Cr(aq)OO(2+) and NO were determined by laser flash photolysis of Cr(aq)NO(2+) in O(2)-saturated acidic aqueous solutions, k = 7 x 10(8) M(-1) s(-1) at 25 degrees C. The reaction produces an intermediate, believed to be NO(2), which was scavenged with ([14]aneN(4))Ni(2+). With limiting NO, the Cr(aq)OO(2+)/NO reaction has a 1:1 stoichiometry and produces both free NO(3)(-) and a chromium nitrato complex, Cr(aq)ONO(2)(2+). In the presence of excess NO, the stoichiometry changes to [NO]/[Cr(aq)OO(2+)] = 3:1, and the reaction produces close to 3 mol of nitrite/mol of Cr(aq)OO(2+). An intermediate, identified as a nitritochromium(III) ion, Cr(aq)ONO(2+), is a precursor to a portion of free NO(2)(-). In the proposed mechanism, the initially produced peroxynitrito complex, Cr(aq)OONO(2+), undergoes O-O bond homolysis followed by some known and some novel chemistry of Cr(aq)O(2+) and NO(2). The reaction between Cr(aq)O(2+) and NO generates Cr(aq)ONO(2+), k > 10(4) M(-1) s(-1). Cr(aq)OO(2+) reacts with NO(2) with k = 2.3 x 10(8) M(-1) s(-1).

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“…The reaction of the nitrosylbis(ethylenediamine)cobalt(III) ion with hydrogen ions produces a species which shall be referred to by the formula Co(en)2(H20)NOH3+. This species has a dissociation constant, for the reaction shown in eq 8, of 1.81 X Co(en)2(H20)NOH33 -2H3 + Co(en)2(OH)N03 (8) 10-3 M2. This value is qualitatively verified by the backtitration experiment.…”

Section: Discussionmentioning

confidence: 99%

“…The solutions containing the aquation reaction products were checked for the presence of hydroxylamine as described by Armor and Buchbinder. 8 No hydroxylamine was detected.…”

Section: Methodsmentioning

confidence: 96%