Figure 2.

A) Various protonation states for His195 adjacent to the FeMoco cluster have been proposed, resulting in marked changes in the preference between N₂‐coordination sites in QM/MM calculations reported by Bjornsson et al.^{[ 16 ]} B) Both a one‐ and two‐side structure have been characterized for the reduced FeMoco unit.^{[ 2 ]} C) In a recent study, Head–Gordon and coworkers proposed that upon (end‐on) coordination, N₂ forms a bridge between Fe2 and Fe6 (i.e., Fe2(m₂:h²–N₂)Fe6) prior to reduction. D) N₂‐activation by a Frustrated Lewis Pair. As recently suggested by Jain et al.,^{[ 37 ]} application of an external electric field aligned with the dipole moment of the transition state can significantly modulate the barrier associated with the breaking of the triple bond.