Differential Reduction of CO2 by Molybdenum and Vanadium Nitrogenases

The molybdenum and vanadium nitrogenases are two homologous enzymes with distinct structural and catalytic features. Previously, it was demonstrated that the V nitrogenase was nearly 700 times more active than its Mo counterpart in reducing CO to hydrocarbons. Herein, a similar discrepancy between the two nitrogenases in the reduction of CO2 is reported, with the V nitrogenase being capable of reducing CO2 to CO, CD4, C2D4, and C2D6, and its Mo counterpart only capable of reducing CO2 to CO. Furthermore, it is shown that the V nitrogenase may direct the formation of CD4 in part via CO2‐derived CO, but that it does not catalyze the formation of C2D4 and C2D6 along this route. The exciting observation of a V nitrogenase‐catalyzed CC coupling with CO2 as the origin of the building blocks adds another interesting reaction to the catalytic repertoire of this unique enzyme system. The differential activities of the V and Mo nitrogenases in CO2 reduction provide an important framework for systematic investigations of this reaction in the future. Vanadium nitrogenase can reduce CO2 to CO, CD4, C2D4, and C2D6. Its ability to reduce CO2 to C2 hydrocarbons adds another important reaction to the catalytic spectrum of the vanadium nitrogenase, that is, a reaction that involves CC coupling from CO2.