AbstractThe activation of dinitrogen (N₂) by transition metals is central to the highly energy intensive, heterogeneous Haber–Bosch process. Considerable progress has been made towards more sustainable homogeneous activations of N₂ with d‐ and f‐block metals, though little success has been had with main group metals. Here we report that the reduction of a bulky magnesium(II) amide [(^TCHPNON)Mg] (^TCHPNON=4,5‐bis(2,4,6‐tricyclohexylanilido)‐2,7‐diethyl‐9,9‐dimethyl‐xanthene) with 5 % w/w K/KI yields the magnesium‐N₂ complex [{K(^TCHPNON)Mg}₂(μ‐N₂)]. DFT calculations and experimental data show that the dinitrogen unit in the complex has been reduced to the N₂²⁻ dianion, via a transient anionic magnesium(I) radical. The compound readily reductively activates CO, H₂ and C₂H₄, in reactions in which it acts as a masked dimagnesium(I) diradical.