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Nitrogen reduction by the Fe sites of synthetic [Mo3S4Fe] cubes

Abstract

Nitrogen (N2) fixation by nature, which is a crucial process for the supply of bio-available forms of nitrogen, is performed by nitrogenase. This enzyme uses a unique transition-metal–sulfur–carbon cluster as its active-site co-factor ([(R-homocitrate)MoFe7S9C], FeMoco)1,2, and the sulfur-surrounded iron (Fe) atoms have been postulated to capture and reduce N2 (refs. 3,4,5,6). Although there are a few examples of synthetic counterparts of the FeMoco, metal–sulfur cluster, which have shown binding of N2 (refs. 7,8,9), the reduction of N2 by any synthetic metal–sulfur cluster or by the extracted form of FeMoco10 has remained elusive, despite nearly 50 years of research. Here we show that the Fe atoms in our synthetic [Mo3S4Fe] cubes11,12 can capture a N2 molecule and catalyse N2 silylation to form N(SiMe3)3 under treatment with excess sodium and trimethylsilyl chloride. These results exemplify the catalytic silylation of N2 by a synthetic metal–sulfur cluster and demonstrate the N2-reduction capability of Fe atoms in a sulfur-rich environment, which is reminiscent of the ability of FeMoco to bind and activate N2.

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Fig. 1: A proposed N2-binding state for FeMoco and a N2-bound Mo–Fe–S cluster in this work.
Fig. 2: Synthesis and chemical modification of N2-bound [Mo3S4Fe] clusters.
Fig. 3: Structural models of N2-bound [Mo3S4Fe] clusters.

Data availability

X-ray data are available free of charge from the Cambridge Crystallographic Data Centre under reference numbers CCDC 20791742079176 and 2141451. All other experimental, spectroscopic, crystallographic and computational data are included in the Supplementary Information.

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Acknowledgements

We thank T. Ohta (Sanyo-Onoda City University) for attempted resonance-Raman measurements of 2a and 15N-labelled 2a. We acknowledge supercomputing resources at the Research Center for Computational Science at Okazaki and the Institute for Chemical Research at Kyoto University (Japan). This work was financially supported by Grant-in-Aids for Scientific Research (19H02733, 20K21207, 21H00021 for Y.O., 20H05671 and 20K21203 for Y.N., 20K15295 for S.K. and 21K20557 for K.T.) from the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), CREST grant (JPMJCR21B1 for Y.O. and JPMJCR1541 for Y.N.) from JST, the Takeda Science Foundation, the Tatematsu Foundation, and the Yazaki Memorial Foundation (for Y.O.), International Collaborative Research Program of ICR, Kyoto University (for Y.O. and W.M.C.S.), and The Kyoto University Research Fund for Young Scientist (Start-Up) (for K.T.).

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Y.O. designed the study. K.M., Y.M., R.H., M.K., K.U. and K.T. conducted the experiments. M.T. participated in the discussion. Y.O. and K.T. interpreted the data. R.E.C. analysed the single-crystal XRD data. W.M.C.S. collected and analysed the computational data. T.T. and Y.S. collected and analysed the Mössbauer spectra. S.K. and Y.N. conducted experiments for ammonia synthesis. Y.O. and K.T. wrote the manuscript with input from all authors.

Corresponding author

Correspondence to Yasuhiro Ohki.

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Supplementary Information

This file describes materials and methods, characterizations of the reported compounds, full results of catalytic evaluations, details of theoretical calculations, and additional discussions that cannot be included in the main text due to the length limit.

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Ohki, Y., Munakata, K., Matsuoka, Y. et al. Nitrogen reduction by the Fe sites of synthetic [Mo3S4Fe] cubes. Nature 607, 86–90 (2022). https://doi.org/10.1038/s41586-022-04848-1

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