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Dinitrosyl Iron Complex [K‐18‐crown‐6‐ether][(NO)2Fe(MePyrCO2)]: Intermediate for Capture and Reduction of Carbon Dioxide
Ist Teil von
Angewandte Chemie (International ed.), 2020-07, Vol.59 (29), p.11819-11823
Auflage
International ed. in English
Ort / Verlag
Germany: Wiley Subscription Services, Inc
Erscheinungsjahr
2020
Link zum Volltext
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Continued efforts are made for the utilization of CO2 as a C1 feedstock for regeneration of valuable chemicals and fuels. Mechanistic study of molecular (electro‐/photo‐)catalysts disclosed that initial step for CO2 activation involves either nucleophilic insertion or direct reduction of CO2. In this study, nucleophilic activation of CO2 by complex [(NO)2Fe(μ‐MePyr)2Fe(NO)2]2− (2, MePyr=3‐methylpyrazolate) results in the formation of CO2‐captured complex [(NO)2Fe(MePyrCO2)]− (2‐CO2, MePyrCO2=3‐methyl‐pyrazole‐1‐carboxylate). Single‐crystal structure, spectroscopic, reactivity, and computational study unravels 2‐CO2 as a unique intermediate for reductive transformation of CO2 promoted by Ca2+. Moreover, sequential reaction of 2 with CO2, Ca(OTf)2, and KC8 established a synthetic cycle, 2 → 2‐CO2 → [(NO)2Fe(μ‐MePyr)2Fe(NO)2] (1) → 2, for selective conversion of CO2 into oxalate. Presumably, characterization of the unprecedented intermediate 2‐CO2 may open an avenue for systematic evaluation of the effects of alternative Lewis acids on reduction of CO2.
In anionic 2, a nucleophilic pyrazolate ligand, the neutral {Fe(NO)2}10 unit, and the [K‐18‐crown‐6‐ether]+ countercation work in concert to promote the capture and nucleophilic activation of CO2 through the assembly of stable 2‐CO2. Relying on the one‐electron reduction power of the {Fe(NO)2}10 core in the anionic complex [(NO)2Fe(MePyrCO2)]−, addition of dicationic Ca2+ further initiates the C−C coupling of activated/reduced CO2 and yields precipitated calcium oxalate.