The Fe–S clusters of nitrogenases carry out the life-sustaining conversion of N₂ to NH₃. Although progress continues to be made in modelling the structural features of nitrogenase cofactors, no synthetic Fe–S cluster has been shown to form a well-defined coordination complex with N₂. Here we report that embedding an [MoFe₃S₄] cluster in a protective ligand environment enables N₂ binding at Fe. The bridging [MoFe₃S₄]₂(μ-η¹:η¹-N₂) complex thus prepared features a substantially weakened N–N bond despite the relatively high formal oxidation states of the metal centres. Substitution of one of the [MoFe₃S₄] cubanes with an electropositive Ti metalloradical induces additional charge transfer to the N₂ ligand with generation of Fe–N multiple-bond character. Structural and spectroscopic analyses demonstrate that N₂ activation is accompanied by shortened Fe–S distances and charge transfer from each Fe site, including those not directly bound to N₂. These findings indicate that covalent interactions within the cluster play a critical role in N₂ binding and activation.

_{Fe–S 固氮酶簇负责将 N 2}转化为 NH ₃以维持生命。尽管在模拟固氮酶辅助因子的结构特征方面继续取得进展，但尚未证明合成的 Fe-S 簇与 N ₂形成明确定义的配位络合物。在这里，我们报告在保护性配体环境中嵌入 [MoFe ₃ S ₄ ] 簇可以使 N ₂与 Fe 结合。桥接 [MoFe ₃ S ₄ ] ₂ (μ-η ¹ :η ¹ -N ₂）尽管金属中心的形式氧化态相对较高，但如此制备的络合物具有显着减弱的 N-N 键。用正电性 Ti 金属自由基取代其中一种 [MoFe ₃ S ₄ ] 立方烷会诱导额外的电荷转移到 N ₂配体，并产生 Fe-N 多键特性。结构和光谱分析表明，N ₂活化伴随着缩短的 Fe-S 距离和来自每个 Fe 位点的电荷转移，包括那些不直接与 N ₂结合的位点。这些发现表明簇内的共价相互作用在 N ₂结合和激活中起着关键作用。