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

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. ^3-6). Although there are a few examples of synthetic counterparts of the FeMoco, metal-sulfur cluster, which have shown binding of N₂ (refs. ^7-9), 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] cubes^11,12 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.