The biological reduction of N₂ to give NH₃ may occur by one of two predominant pathways in which nitrogenous N_xH_y intermediates, including hydrazine (N₂H₄), diazene (N₂H₂), nitride (N³⁻) and imide (NH²⁻), may be involved. To test the validity of hypotheses on iron's direct role in the stepwise reduction of N₂, model systems for iron are needed. Such systems can test the chemical compatibility of iron with various proposed N_xH_y intermediates and the reactivity patterns of such species. Here we describe a trigonal bipyramidal Si(o-C₆H₄PR₂)₃Fe–L scaffold (R = Ph or i-Pr) in which the apical site is occupied by nitrogenous ligands such as N₂, N₂H₄, NH₃ and N₂R. The system accommodates terminally bound N₂ in the three formal oxidation states (iron(0), +1 and +2). N₂ uptake is demonstrated by the displacement of its reduction partners NH₃ and N₂H₄, and N₂ functionalizaton is illustrated by electrophilic silylation.