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A thiolate-bridged FeIVFeIV μ-nitrido complex and its hydrogenation reactivity toward ammonia formation

Abstract

Iron nitrides are key intermediates in biological nitrogen fixation and the industrial Haber–Bosch process, used to form ammonia from dinitrogen. However, the proposed successive conversion of nitride to ammonia remains elusive. In this regard, the search for well-described multi-iron nitrido model complexes and investigations on controlling their reactivity towards ammonia formation have long been of great challenge and importance. Here we report a well-defined thiolate-bridged FeIVFeIV μ-nitrido complex featuring an uncommon bent Fe–N–Fe moiety. Remarkably, this complex shows excellent reactivity toward hydrogenation with H2 at ambient conditions, forming ammonia in high yield. Combined experimental and computational studies demonstrate that a thiolate-bridged FeIIIFeIII μ-amido complex is a key intermediate, which is generated through an unusual two-electron oxidation of H2. Moreover, ammonia production was also realized by treating this diiron μ-nitride with electrons and water as a proton source.

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Fig. 1: Iron nitrides proposed as key intermediates in N2 reduction to NH3.
Fig. 2: Synthesis and characterization of thiolate-bridged diiron μ-nitrido complex.
Fig. 3: MO diagram of complex 3+ obtained by PBE/def2-TZVP calculations.
Fig. 4: Ammonia formation from diiron μ-nitride complex 3[BPh4].
Fig. 5: Computed reaction profile for hydrogenation of 3+ to liberate ammonia, obtained by PBE/def2-TZVP calculations.

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Data availability

All data resulting from the experimental and computational studies of this work are included within this Article and the Supplementary Information. Crystallographic data for the structures reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 1400911 (2[PF6]·THF), 1435241 (3[BPh4] at 100 K), 2108184 (3[BPh4] at 298 K), 1402944 (4[BPh4]·0.5THF), 1402945 (5[BPh4]) and 2089536 (6). Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/.

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (grants nos. 21690064, 22001031 and 21231003), Key Laboratory of Bio-based Chemicals of Liaoning Province of China and the ‘111’ project of the Ministry of Education of China. J.Q. would like to especially thank M. Hidai from the University of Tokyo for his continuous guidance and valuable support. We would also like to express our gratitude to E. Bill and B. Mienert of the Max-Planck Institute for Chemical Energy Conversion (MPI-CEC) for help with the acquisition of the Mössbauer data, as well as for fruitful discussions.

Author information

Authors and Affiliations

Authors

Contributions

J.Q. and B.W. supervised the project. J.Q. and J.Z. conceived and designed the experiments. Y. Zhang, J.Z., D.Y. and T.M. performed the experiments. J.W. and S.Y. performed the Mössbauer measurements. S.Y. and H.C. carried out quantum chemical calculations. J.Q., S.Y., B.W., D.Y. and Y. Zhang co-wrote the paper. S.Y., Y. Zhou, J.Z., D.Y. and Y. Zhang analysed the data. All authors discussed the results in detail and commented on the manuscript.

Corresponding authors

Correspondence to Shengfa Ye or Jingping Qu.

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Nature Chemistry thanks the anonymous reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–46, Tables 1–19 and Discussion.

Supplementary Data 1

Crystallographic data for compound 2[PF6]·THF. CCDC reference 1400911.

Supplementary Data 2

Crystallographic data for compound 3[BPh4] at 100 K. CCDC reference 1435241.

Supplementary Data 3

Crystallographic data for compound 3[BPh4] at 298 K. CCDC reference 2108184.

Supplementary Data 4

Crystallographic data for compound 4[BPh4]·0.5THF. CCDC reference 1402944.

Supplementary Data 5

Crystallographic data for compound 5[BPh4]. CCDC reference 1402945.

Supplementary Data 6

Crystallographic data for compound 6. CCDC reference 2089536.

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Zhang, Y., Zhao, J., Yang, D. et al. A thiolate-bridged FeIVFeIV μ-nitrido complex and its hydrogenation reactivity toward ammonia formation. Nat. Chem. 14, 46–52 (2022). https://doi.org/10.1038/s41557-021-00852-6

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