Coordination and Activation of N2 at Low-Valent Magnesium using a Cooperative 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, heterogenous 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(-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.