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130th General Meeting of Korean Chemical Society NOx Conversion with Nickel

Submission Date :
8 / 2 / 2022 , 11 : 41 : 31
Abstract Number :
Presenting Type:
Presenting Area :
Inorganic Chemistry - Evolution of Inorganic Chemistry
Authors :
Yunho Lee
Department of Chemistry, Seoul National University, Korea
Assigned Code :
Presenting Time :
Denitrification is biological NOx conversion, which occurs via a multi-step process to reduce nitrate to dinitrogen (NO3– → NO2– → NO → N2O → N2) as a part of biological nitrogen cycle. Although the efficient enzymatic reactions attractively operate under mild conditions, four different metalloenzymes are needed to convert a series of intermediate NOx species. Due to the complications of such a reaction pathway, a biological method is, unfortunately, difficult to apply in an industrial NOx conversion process. Distinct from the biological NOx transformation, we have developed a synthetic approach to this issue by utilizing a bifunctional metal catalyst for producing value-added products from NOx. Based on the theoretical evaluation on the free energy change of the nitrate reduction series, the sequential reductions of NO3– to N2 is downhill, when CO is utilized. Thus, bioinspired deoxygenation of NOx coupled with organometallic reactions has been explored. In this presentation, a novel catalysis based on a Ni pincer system will be presented. The catalysis starts with converting Ni–NOx to Ni–NO via deoxygenation with CO(g), which is followed by transfer of the in-situ generated nitroso group to organic substrates. The transfer favorably occurs at the flattened Ni(I)–NO site via its nucleophilic reaction. Successful catalytic production of oximes from benzyl halides using NaNO2 is presented with a turnover number of >200 under mild conditions. In a key step of the catalysis, a nickel(I)–•NO species activates alkyl halides, which is carefully evaluated by both experimental and theoretical methods. Our nickel catalyst effectively fulfils a dual-purpose, namely deoxygenating NOx anions and catalyzing C–N coupling.