Ammonia formation by a thiolate-bridged diiron amide complex as a nitrogenase mimic

Abstract

Although nitrogenase enzymes routinely convert molecular nitrogen into ammonia under ambient temperature and pressure, this reaction is currently carried out industrially using the Haber–Bosch process, which requires extreme temperatures and pressures to activate dinitrogen. Biological fixation occurs through dinitrogen and reduced NxHy species at multi-iron centres of compounds bearing sulfur ligands, but it is difficult to elucidate the mechanistic details and to obtain stable model intermediate complexes for further investigation. Metal-based synthetic models have been applied to reveal partial details, although most models involve a mononuclear system. Here, we report a diiron complex bridged by a bidentate thiolate ligand that can accommodate HN=NH. Following reductions and protonations, HN=NH is converted to NH3 through pivotal intermediate complexes bridged by N2H3– and NH2– species. Notably, the final ammonia release was effected with water as the proton source. Density functional theory calculations were carried out, and a pathway of biological nitrogen fixation is proposed. Although it is achieved routinely by nitrogenases, the conversion of molecular dinitrogen into ammonia under ambient conditions is proving difficult with synthetic systems. A thiolate-bridged diiron complex has now been developed that produces ammonia from coordinated N2H2 through a sequence of reduction and protonation reactions that may well mimic the biological nitrogen fixation.

Cite this article

Li, Y., Li, Y., Wang, B. et al. Ammonia formation by a thiolate-bridged diiron amide complex as a nitrogenase mimic. Nature Chem 5, 320–326 (2013). https://doi.org/10.1038/nchem.1594

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