Triggering N_2 uptake via redox-induced expulsion of coordinated NH_3 and N_2 silylation at trigonal bipyramidal iron

Abstract

The biological reduction of N_2 to give NH_3 may occur by one of two predominant pathways in which nitrogenous N_xH_y intermediates, including hydrazine (N_2H_4), diazene (N_2H_2), nitride (N^(3-)) and imide (NH^(2-)), may be involved. To test the validity of hypotheses on iron's direct role in the stepwise reduction of N_2, 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-C_6H_4PR_2)_3Fe–L scaffold (R=Ph or i-Pr) in which the apical site is occupied by nitrogenous ligands such as N_2, N_2H_4, NH_3 and N_2R. The system accommodates terminally bound N_2 in the three formal oxidation states (iron(0), +1 and +2). N_2 uptake is demonstrated by the displacement of its reduction partners NH_3 and N_2H_4, and N_2 functionalizaton is illustrated by electrophilic silylation.

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