Synthesis, Characterization, and Nitrogenase-Relevant Reactions of an Iron Sulfide Complex with a Bridging Hydride

The FeMoco of nitrogenase is an iron–sulfur cluster with exceptional bond-reducing abilities. ENDOR studies have suggested that E₄, the state that binds and reduces N₂, contains bridging hydrides as part of the active-site iron-sulfide cluster. However, there are no examples of any isolable iron-sulfide cluster with a hydride, which would test the feasibility of such a species. Here, we describe a diiron sulfide hydride complex that is prepared using a mild method involving C–S cleavage of added thiolate. Its reactions with nitrogenase substrates show that the hydride can act as a base or nucleophile and that reduction can cause the iron atoms to bind N₂. These results add experimental support to hydride-based pathways for nitrogenase