Examining the relationship between coordination mode and reactivity of dinitrogen

Molecular nitrogen (N-2) is the most abundant gas in Earth's atmosphere, but its low reactivity has hampered its use as a precursor to higher value nitrogen-containing compounds. Coordination of N-2 to metal centres offers a way to overcome this intrinsic inertness and allows the discovery of new transformations. The expanding family of isolable N-2 coordination complexes exhibits various bonding modes that, in particular cases, facilitate catalytic or stoichiometric transformations of the N-2 unit. In this Review, we survey metal complexes of N-2 in order to correlate bonding mode with functionalization propensity. Although many factors influence the functionalization of N-2, we propose that coordination mode could be more important than previously recognized.