title: Stepwise N-H Bond Formation From N2-Derived Iron Nitride, Imide and Amide Intermediates to Ammonia.
abstract: Reduction of N2to ammonia in nature and in electrocatalysis takes place through 1-proton/1-electron steps, motivating efforts to experimentally study the steps during proton/electron transfer to well-characterized N2-derived species with bridging nitrides. We report here the protonation and reduction reactions of an N2-derived iron bis(nitride) complex (Rodriguezet al., Science, 2011,334, 780). We isolate and definitively characterize triiron imido and amido intermediates that lie along the path to ammonia formation, and Mössbauer spectroscopy shows the oxidation level of iron atoms in these mixed-valence clusters. The first two H atoms add to one of the two nitrides of the bis(nitride) complex, and the proton-coupled electron transfer in the second step can be concerted or stepwise depending on the sources of protons and electrons. The characterization of partially protonated nitrides and their mechanisms of formation are expected to guide efforts to convert N2to ammonia with mild acids.
authors.affiliation: Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States.
authors.forename: K Cory
authors.initials: KC
authors.lastname: MacLeod
authors.affiliation: Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States.
authors.forename: Sean F
authors.initials: SF
authors.lastname: McWilliams
authors.affiliation: Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States.
authors.forename: Brandon Q
authors.initials: BQ
authors.lastname: Mercado
authors.affiliation: Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States.
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Holland