Understanding the mechanisms to activate and functionalize dinitrogen (N 2 ) is of great importance for the rational design of nitrogen-fixation catalysts. Reactions of gas-phase species with N 2 are being actively studied to understand the bond activation and formation processes at a strictly molecular level. This Perspective provides an overview of the recent progress in combined experimental and theoretical studies on the activation and functionalization of N 2 by gas-phase metal species. New mechanistic insights into N 2 molecular adsorption, NN cleavage, and N−X (X = C, B, and H) formation have been introduced, in which the new reaction channels of ejecting neutral metal fragments and the coupling reactions of N 2 with other molecules are highlighted. Finally, the current challenges and outlooks of N 2 activation in the gas phase are discussed as well.

Alkali atoms are usually used as promoters to significantly increase the catalytic activity of transition-metal catalysts in a wide range of reactions such as dinitrogen conversion reactions. However, the role of alkali metal atoms remains controversial. Herein, a series of quaternary cluster anions containing lithium atoms Nb 2 LiNO 1−4 − have been synthesized and reacted with N 2 at room temperature. The detailed experimental and theoretical investigations indicate that Nb 2 LiNO − is capable to cleave the NN bond and the Li atoms in Nb 2 LiNO 1,2 − act as electron donors in the N 2 reduction reaction. With the increase in the number of oxygen atoms, the reactivity toward N 2 is reduced from adsorption via a side-on end-on mode in Nb 2 LiNO 2 − to the inertness of Nb 2 LiNO 4 − . In Nb 2 LiNO 3,4 − anions, the Li atoms are bonded with oxygen atoms, acting as structural units to stabilize structures. Therefore, the roles of alkali atoms are able to change with different chemical environments of active sites. For the first time, we reveal how the number of ligands (oxygen atoms herein) can be used to finely regulate the reactivity toward N 2 .