Nitrogen adsorption on Nb 2 C 6 H 4 + cations: the important role of benzyne ( ortho -C 6 H 4 ).

N 2 adsorption is a prerequisite for activation and transformation. Time-of-flight mass spectrometry experiments show that the Nb 2 C 6 H 4 + cation, resulting from the gas-phase reaction of Nb 2 + with C 6 H 6 , is more favorable for N 2 adsorption than Nb + and Nb 2 + cations. Density functional theory calculations reveal the effect of the ortho -C 6 H 4 ligand on N 2 adsorption. In Nb 2 C 6 H 4 + , interactions between the Nb-4d and C-2p orbitals enable the Nb 2 + cation to form coordination bonds with the ortho -C 6 H 4 ligand. Although the ortho -C 6 H 4 ligand in Nb 2 C 6 H 4 + is not directly involved in the reaction, its presence increases the polarity of the cluster and brings the highest occupied molecular orbital (HOMO) closer to the lowest occupied molecular orbital (LUMO) of N 2 , thereby increasing the N 2 adsorption energy, which effectively facilitates N 2 adsorption and activation. This study provides fundamental insights into the mechanisms of N 2 adsorption in "transition metal-organic ligand" systems.