Generation of the NCN Radical from Co-Conversion of N2 and CO2 Mediated by the Niobium Oxide Cluster Anion Nb2O3.

Cyanonitrene radical (NCN) is a valuable species involved in many subareas of chemistry including combustion, atmospheric, interstellar, and synthetic chemistry. However, the generation of NCN via C─N coupling from the abundantly available molecules N2 and CO2 remains a significant challenge due to the inertness of their chemical bonds and competing side reactions. In this study, by using state-of-the-art mass spectrometry and quantum chemistry calculations, the niobium oxide cluster anion Nb2O3 - is shown to enable the co-conversion of N2 and CO2 at room temperature, achieving the formation of two C─N bonds and the generation of a free NCN radical upon external energy input. The prior complete dissociation of N2 on Nb2O3 - was found to generate two bridgingly bonded nitrogen atoms (Nb), together with adjacent metal centers, which function as Lewis acid-base pairs (Nbδ+─Nδ-) to activate CO2, leading to the spontaneous formation of the first C─N bond. The nitrogen-centered radicals and dinuclear metal (Nb) centers play pivotal roles in promoting the formation of the second C─N bond and in facilitating the removal of two oxygen atoms from CO2, culminating in the generation of NCN. This study introduces a novel route for NCN radical generation through the unprecedented co-conversion of N2 and CO2.