Dinitrogen Activation by Heteronuclear Metal Carbide Cluster Anions Y_1‐3CoC_1,2⁻: An Experimental and DFT Study

Abstract

Mass spectrometry was used to observe the reactions between Y‐Co heteronuclear metal carbide cluster anions Y1‐3CoC1,2– and N2 at room temperature. Y2CoC1,2– can produce Co ejection products, in which Y2CoC– also has N2 association products; YCoC2– and Y3CoC– only generate N2 association products, while YCoC– and Y3CoC2– are inert to N2. Detailed reaction pathways were obtained through density functional theory calculations, which reasonably explain the experimental phenomena. Co is superior to Y as the electrophilic reaction site in the clusters and is the preferential initial adsorption site for N2. Some crucial steps were identified, including N–N dissociation, CC–N formation, C−CN dissociation, and C−N formation. The energy barriers of these steps are closely related to the coordination mode of N/N2 and C/C2 in clusters. Two indicators, the N–N bond length and the Mayer bond order, were utilized to describe the activation degree of the N–N bond. Analyses on the density of states and the frontier molecular orbitals reveal the electronic structures of key intermediates for N–N dissociation. The reaction mechanisms of N2 activation on Y‐Co carbide clusters obtained may lay a preliminary foundation for the further development of catalysts for nitrogen reduction reaction (NRR).

Toward Designing Reactive Metal Clusters for Dinitrogen Activation: A Guideline Based on N2 Initial Adsorption

“…In this regard, the study of gas-phase reactions under isolated conditions with well-characterized chemical and molecular structures − constitutes an alternative way to probe the intrinsic structure–reactivity relationship of N 2 activation by metal clusters. With continuous efforts from many research groups, to date, a variety of homo/heteronuclear metal clusters have been successfully identified to be capable of fully cleaving the NN triple bond, − the metal centers of which include Ti 2 , Gd 2 , Ta 2 , − , Ta 3 , Ta 4 , Ta 6 , FeTa, V 3 , , FeV 2 , Sc 2 , Nb, ,, etc., as summarized in Figure . Considering the high NN bond strength, the mechanistic focus of these studies was often to elucidate the NN cleavage pathway.…”