Living systems carry out the reduction of N₂ to ammonia (NH₃) through a series of protonation and electron transfer steps under ambient conditions using the enzyme nitrogenase. In the chemical industry, the Haber–Bosch process hydrogenates N₂ but requires high temperatures and pressures. Both processes rely on iron-based catalysts, but molecular iron complexes that promote the formation of NH₃ on addition of H₂ to N₂ have remained difficult to devise. Here, we isolate the tri(iron)bis(nitrido) complex [(Cp′Fe)₃(μ₃-N)₂] (in which Cp′ = η⁵-1,2,4-(Me₃C)₃C₅H₂), which is prepared by reduction of [Cp′Fe(μ-I)]₂ under an N₂ atmosphere and comprises three iron centres bridged by two μ₃-nitrido ligands. In solution, this complex reacts with H₂ at ambient temperature (22 °C) and low pressure (1 or 4 bar) to form NH₃. In the solid state, it is converted into the tri(iron)bis(imido) species, [(Cp′Fe)₃(μ₃-NH)₂], by addition of H₂ (10 bar) through an unusual solid–gas, single-crystal-to-single-crystal transformation. In solution, [(Cp′Fe)₃(μ₃-NH)₂] further reacts with H₂ or H⁺ to form NH₃.

生命系统在环境条件下使用酶氮酶通过一系列质子化和电子转移步骤将N ₂还原为氨（NH ₃）。在化学工业中，Haber–Bosch工艺将N ₂氢化，但需要高温和高压。这两种方法都依赖于铁基催化剂，但促进NH的形成分子铁络合物₃上添加H ₂到N ₂仍然很难设计。在这里，我们分离出三（铁）二（次氮）配合物[（Cp'Fe）₃（μ ₃ -N）₂ ]（其中的Cp'=η ⁵ -1,2,4-（ME ₃ C）₃ c ^ ₅ ħ ₂），这是由减少的[Cp'Fe（μ-I）]制备₂的N下₂气氛和包括三个铁中心桥接由两个μ _3个-nitrido配体。在溶液中，该络合物在环境温度（22°C）和低压（1或4 bar）下与H ₂反应形成NH ₃。在固体状态，它被转换成三（铁）双（亚氨基）物种，[（Cp'Fe）₃（μ ₃ -NH）₂ ]，由添加H ₂通过一个不寻常的固（10巴）气体，单晶至单晶转变。在溶液中，[（Cp'Fe）₃（μ ₃ -NH）₂ ]进一步与H ₂或H ⁺反应形成NH ₃。