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Reductive Coupling of Nitric Oxide by Cu(I): Stepwise Formation of Mono- and Dinitrosyl Species En Route to a Cupric Hyponitrite Intermediate

Bhadra M, Albert T, Franke A, Josef V, Ivanovic-Burmazovic I, Swart M, Moënne-Loccoz P, Karlin KD (2023)

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Publication Type: Journal article

Publication year: 2023

Journal

Book Volume: 145

Pages Range: 2230-2242

Journal Issue: 4

DOI: 10.1021/jacs.2c09874

Abstract

Transition-metal-mediated reductive coupling of nitric oxide (NO(g)) to nitrous oxide (N2O(g)) has significance across the fields of industrial chemistry, biochemistry, medicine, and environmental health. Herein, we elucidate a density functional theory (DFT)-supplemented mechanism of NO(g) reductive coupling at a copper-ion center, [(tmpa)Cu^I(MeCN)]⁺ (1) {tmpa = tris(2-pyridylmethyl)amine}. At −110 °C in EtOH (<−90 °C in MeOH), exposing 1 to NO(g) leads to a new binuclear hyponitrite intermediate [{(tmpa)Cu^II}2(μ-N2O2^2-)]²⁺ (2), exhibiting temperature-dependent irreversible isomerization to the previously characterized κ²-O,O′-trans-[(tmpa)2Cu2^II(μ-N2O2^2-)]²⁺ (OO^Xray) complex. Complementary stopped-flow kinetic analysis of the reaction in MeOH reveals an initial mononitrosyl species [(tmpa)Cu(NO)]⁺ (1-(NO)) that binds a second NO molecule, forming a dinitrosyl species [(tmpa)Cu^II(NO)2] (1-(NO)2). The decay of 1-(NO)2 requires an available starting complex 1 to form a dicopper-dinitrosyl species hypothesized to be [{(tmpa)Cu}2(μ-NO)2]²⁺ (D) bearing a diamond-core motif, en route to the formation of hyponitrite intermediate 2. In contrast, exposing 1 to NO(g) in 2-MeTHF/THF (v/v 4:1) at <−80 °C leads to the newly observed transient metastable dinitrosyl species [(tmpa)Cu^II(NO)2] (1-(NO)2) prior to its disproportionation-mediated transformation to the nitrite product [(tmpa)Cu^II(NO2)]⁺. Our study furnishes a near-complete profile of NO(g) activation at a reduced Cu site with tripodal tetradentate ligation in two distinctly different solvents, aided by detailed spectroscopic characterization of metastable intermediates, including resonance Raman characterization of the new dinitrosyl and hyponitrite species detected.

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APA:

Bhadra, M., Albert, T., Franke, A., Josef, V., Ivanovic-Burmazovic, I., Swart, M.,... Karlin, K.D. (2023). Reductive Coupling of Nitric Oxide by Cu(I): Stepwise Formation of Mono- and Dinitrosyl Species En Route to a Cupric Hyponitrite Intermediate. Journal of the American Chemical Society, 145(4), 2230-2242. https://dx.doi.org/10.1021/jacs.2c09874

MLA:

Bhadra, Mayukh, et al. "Reductive Coupling of Nitric Oxide by Cu(I): Stepwise Formation of Mono- and Dinitrosyl Species En Route to a Cupric Hyponitrite Intermediate." Journal of the American Chemical Society 145.4 (2023): 2230-2242.

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