Coordination and Activation of N₂ at Low-Valent Magnesium using a Heterobimetallic Approach: Synthesis and Reactivity of a Masked Dimagnesium Diradical**

The 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.