Nitrogen reduction by the Fe sites of synthetic [MoSFe] cubes.

Nitrogen (N) 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)MoFeSC], FeMoco), and the sulfur-surrounded iron (Fe) atoms have been postulated to capture and reduce N (refs. ). Although there are a few examples of synthetic counterparts of the FeMoco, metal-sulfur cluster, which have shown binding of N (refs. ), the reduction of N by any synthetic metal-sulfur cluster or by the extracted form of FeMoco has remained elusive, despite nearly 50 years of research. Here we show that the Fe atoms in our synthetic [MoSFe] cubes can capture a N molecule and catalyse N silylation to form N(SiMe) under treatment with excess sodium and trimethylsilyl chloride. These results exemplify the catalytic silylation of N by a synthetic metal-sulfur cluster and demonstrate the N-reduction capability of Fe atoms in a sulfur-rich environment, which is reminiscent of the ability of FeMoco to bind and activate N.