Dinitrosyl Iron Complex [K‐18‐crown‐6‐ether][(NO)2Fe(MePyrCO2)]: Intermediate for Capture and Reduction of Carbon Dioxide

Continued efforts are made on utilization of CO 2 as a C 1 feedstock for regeneration of valuable chemicals and fuels. Mechanistic study of molecular (electro-/photo-)catalysts disclosed that initial step for CO 2 activation involves either nucleophilic insertion or direct reduction of CO 2 . In this study, nucleophilic activation of CO 2 by complex [(NO) 2 Fe(mu- Me Pyr) 2 Fe(NO) 2 ] 2- ( 2 , Me Pyr = 3-methylpyrazolate) results in the formation of CO 2 -captured complex [(NO) 2 Fe( Me PyrCO 2 )] - ( 2-CO 2 , Me PyrCO 2 = 3-methyl-pyrazole-1-carboxylate). Single-crystal structure, spectroscopic, reactivity, and computational study unravels 2-CO 2 as a unique intermediate for reductive transformation of CO 2 promoted by Ca 2+ . Moreover, sequential reaction of 2 with CO 2 , Ca(OTf) 2 , and KC 8 established a synthetic cycle, 2 --> 2-CO 2 --> [(NO) 2 Fe(mu- Me Pyr) 2 Fe(NO) 2 ] ( 1 ) --> 2 , for selective conversion of CO 2 into oxalate. Presumably, characterization of the unprecedented intermediate 2-CO 2 may open an avenue for systematic evaluation of the effects of alternative Lewis acids on reduction of CO 2 .