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Article Dans Une Revue Nature Chemistry Année : 2020

NH3 formation from N2 and H2 mediated by molecular tri-iron complexes

Yannick Coppel

Résumé

Living systems carry out the reduction of N2 to ammonia (NH3) through a series of protonation and electron transfer steps under ambient conditions using the enzyme nitrogenase. In the chemical industry, the Haber-Bosch process hydrogenates N2 but requires high temperatures and pressures. Both processes rely on iron-based catalysts, but molecular iron complexes that promote the formation of NH3 on addition of H2 to N2 have remained difficult to devise. Here, we isolate the tri(iron)bis(nitrido) complex [(Cp'Fe)3(μ3-N)2] (in which Cp' = η5-1,2,4-(Me3C)3C5H2), which is prepared by reduction of [Cp'Fe(μ-I)]2 under an N2 atmosphere and comprises three iron centres bridged by two μ3-nitrido ligands. In solution, this complex reacts with H2 at ambient temperature (22 °C) and low pressure (1 or 4 bar) to form NH3. In the solid state, it is converted into the tri(iron)bis(imido) species, [(Cp'Fe)3(μ3-NH)2], by addition of H2 (10 bar) through an unusual solid-gas, single-crystal-to-single-crystal transformation. In solution, [(Cp'Fe)3(μ3-NH)2] further reacts with H2 or H+ to form NH3.
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Dates et versions

hal-03150029 , version 1 (23-02-2021)

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Matthias Reiners, Dirk Baabe, Katharina Münster, Marc-Kevin Zaretzke, Matthias Freytag, et al.. NH3 formation from N2 and H2 mediated by molecular tri-iron complexes. Nature Chemistry, 2020, 12 (8), pp.740-746. ⟨10.1038/s41557-020-0483-7⟩. ⟨hal-03150029⟩
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