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Nitrogen reduction and functionalization by a multimetallic uranium nitride complex

机译：多金属氮化铀络合物的氮还原和功能化

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Molecular nitrogen (N-2) is cheap and widely available, but its unreactive nature is a challenge when attempting to functionalize it under mild conditions with other widely available substrates (such as carbon monoxide, CO) to produce value-added compounds. Biological N-2 fixation can do this, but the industrial Haber-Bosch process for ammonia production operates under harsh conditions (450 degrees Celsius and 300 bar), even though both processes are thought to involve multimetallic catalytic sites(1,2). And although molecular complexes capable of binding and even reducing N-2 under mild conditions are known, with co-operativity between metal centres considered crucial for the N-2 reduction step(1-14), the multimetallic species involved are usually not well defined, and further transformation of N-2-binding complexes to achieve N-H or N-C bond formation is rare(2,6,8,10,15,16). Haber noted(17), before an iron-based catalyst was adopted for the industrial Haber-Bosch process, that uranium and uranium nitride materials are very effective heterogeneous catalysts for ammonia production from N-2. However, few examples of uranium complexes binding N-2 are known(18-22), and soluble uranium complexes capable of transforming N-2 into ammonia or organonitrogen compounds have not yet been identified. Here we report the four-electron reduction of N-2 under ambient conditions by a fully characterized complex with two U-iii ions and three K+ centres held together by a nitride group and a flexible metalloligand framework. The addition of H-2 and/or protons, or CO to the resulting N-2(4-) complex results in the complete cleavage of N-2 with concomitant N-2 functionalization through N-H or N-C bond-forming reactions. These observations establish that a molecular uranium complex can promote the stoichiometric transformation of N-2 into NH3 or cyanate, and that a flexible, electron-rich, multimetallic, nitride-bridged core unit is a promising starting point for the design of molecular complexes capable of cleaving and functionalizing N-2 under mild conditions.
机译：分子氮（N-2）便宜且可广泛获得，但是当试图在温和条件下将其与其他广泛可获得的底物（例如一氧化碳，CO）进行功能化以生产增值化合物时，其非反应性是一个挑战。生物固氮N-2可以做到这一点，但是工业上用于氨气生产的Haber-Bosch工艺在苛刻的条件下（450摄氏度和300 bar）运行，即使两种工艺都涉及多金属催化位点（1,2）。并且尽管已知能够在温和条件下结合甚至还原N-2的分子复合物，但金属中心之间的协同作用被认为对N-2还原步骤至关重要（1-14），但涉及的多金属物种通常没有很好的定义以及进一步转化N-2-结合复合物以实现NH或NC键形成的现象很少（2,6,8,10,15,16）。 Haber指出（17），在将铁基催化剂用于工业Haber-Bosch工艺之前，铀和氮化铀材料是用于从N-2生产氨的非常有效的非均相催化剂。然而，很少有结合N-2的铀络合物的例子[18-22]，并且尚未发现能够将N-2转化为氨或有机氮化合物的可溶性铀络合物。在这里，我们报告了在环境条件下N-2的四电子还原，该复合物具有完全特征化的配合物，其中两个U-iii离子和三个K +中心由氮化物基团和柔性金属配体骨架结合在一起。将H-2和/或质子或CO添加到所得的N-2（4-）络合物中会导致N-2完全裂解，并伴随通过N-H或N-C键形成反应进行的N-2官能化。这些观察结果表明，分子铀络合物可以促进N-2的化学计量转化为NH3或氰酸盐，并且灵活的，富电子，多金属，氮化物桥联的核心单元是设计具有能力的分子络合物的有希望的起点温和条件下裂解和功能化N-2的过程。

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  • 来源
    《Nature》 |2017年第7663期|332-335|共4页
  • 作者

    Falcone Marta; Chatelain Lucile; Scopelliti Rosario; Zivkovic Ivica; Mazzanti Marinella;

  • 作者单位

    Ecole Polytech Fed Lausanne, Inst Sci & Ingn Chim, CH-1015 Lausanne, Switzerland;

    Ecole Polytech Fed Lausanne, Inst Sci & Ingn Chim, CH-1015 Lausanne, Switzerland;

    Ecole Polytech Fed Lausanne, Inst Sci & Ingn Chim, CH-1015 Lausanne, Switzerland;

    Ecole Polytech Fed Lausanne, Inst Phys, Lab Quantum Magnetism, CH-1015 Lausanne, Switzerland;

    Ecole Polytech Fed Lausanne, Inst Sci & Ingn Chim, CH-1015 Lausanne, Switzerland;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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