TY - JOUR
T1 - Reductive Coupling of Nitric Oxide by Cu(I)
T2 - Stepwise Formation of Mono- and Dinitrosyl Species En Route to a Cupric Hyponitrite Intermediate
AU - Bhadra, Mayukh
AU - Albert, Therese
AU - Franke, Alicja
AU - Josef, Verena
AU - Ivanović-Burmazović, Ivana
AU - Swart, Marcel
AU - Moënne-Loccoz, Pierre
AU - Karlin, Kenneth D.
N1 - Funding Information:
The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of NIH or the aforesaid scientific bodies. The authors acknowledge the usage of the EPR instrument housed in the Instrumentation Facility (DCIF) of the Department of Chemistry at MIT for experiments during the revision of the manuscript.
Funding Information:
This research was supported by the National Institutes of Health and the Spanish Ministry of Science, the Bayerisches Staatsministerium für Wissenschaft und Kunst, and the appropriate grants are gracefully acknowledged (GM28962 to K.D.K.; GM74785 to P.M.L., and CTQ2017-87392-P/PID2020-114548GB-I00 to M.S.)
Publisher Copyright:
© 2023 American Chemical Society.
PY - 2023/2/1
Y1 - 2023/2/1
N2 - 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)CuI(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)CuII}2(μ-N2O22-)]2+ (2), exhibiting temperature-dependent irreversible isomerization to the previously characterized κ2-O,O′-trans-[(tmpa)2Cu2II(μ-N2O22-)]2+ (OOXray) 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)CuII(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)CuII(NO)2] (1-(NO)2) prior to its disproportionation-mediated transformation to the nitrite product [(tmpa)CuII(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.
AB - 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)CuI(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)CuII}2(μ-N2O22-)]2+ (2), exhibiting temperature-dependent irreversible isomerization to the previously characterized κ2-O,O′-trans-[(tmpa)2Cu2II(μ-N2O22-)]2+ (OOXray) 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)CuII(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)CuII(NO)2] (1-(NO)2) prior to its disproportionation-mediated transformation to the nitrite product [(tmpa)CuII(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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U2 - 10.1021/jacs.2c09874
DO - 10.1021/jacs.2c09874
M3 - Article
C2 - 36652374
AN - SCOPUS:85146546506
SN - 0002-7863
VL - 145
SP - 2230
EP - 2242
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 4
ER -