Liang Liu, Samantha I Johnson, Aaron M Appel, R Morris Bullock
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引用次数: 0
摘要
在寻求可持续清洁能源的过程中,氨是一种前景广阔的候选物质。由于氨具有作为能量载体的能力,氨的氧化为以碳中性方法解决全球日益增长的能源需求开辟了道路。我们报告了一种地球上丰富的过渡金属复合物--反式[LFeII(MeCN)2][PF6]2--对氨的催化化学氧化作用,其中 L 是一种大环配体,带有四个 N-杂环碳烯(NHC)供体。利用 MeCN 中的三芳基铵自由基阳离子,在铁催化剂负载量极低(0.043 mM,0.004 mol % 催化剂)的情况下,通过化学催化获得了每铁 182 次的 N2 转化。这种化学催化成功过渡到了氨氧化的介导电催化。铁催化剂和介质 (p-MeOC6H4)3N 的分子电催化在 MeCN 中的催化半波电位(Ecat/2)为 0.18 V vs [Cp2Fe]+/0,在 -20 °C 的受控电位电解中,应用 0.20 V vs [Cp2Fe]+/0的电位实现了 9.3 次 N2 转化,法拉第效率为 75%。根据计算结果,该催化剂依次经过氧化和去质子化步骤形成 [LFeIV(NH2)2]2+,然后经过双金属耦合形成 N-N 键。
Oxidation of Ammonia Catalyzed by a Molecular Iron Complex: Translating Chemical Catalysis to Mediated Electrocatalysis.
Ammonia is a promising candidate in the quest for sustainable, clean energy. With its capacity to serve as an energy carrier, the oxidation of ammonia opens avenues for carbon-neutral approaches to address worldwide growing energy needs. We report the catalytic chemical oxidation of ammonia by an Earth-abundant transition metal complex, trans-[LFeII(MeCN)2][PF6]2, where L is a macrocyclic ligand bearing four N-heterocyclic carbene (NHC) donors. Using triarylaminium radical cations in MeCN, up to 182 turnovers of N2 per Fe were obtained from chemical catalysis with an extremely low loading of the Fe catalyst (0.043 mM, 0.004 mol % catalyst). This chemical catalysis was successfully transitioned to mediated electrocatalysis for the oxidation of ammonia. Molecular electrocatalysis by the Fe catalyst and the mediator (p-MeOC6H4)3N exhibited a catalytic half-wave potential (Ecat/2) of 0.18 V vs [Cp2Fe]+/0 in MeCN, and achieved 9.3 turnovers of N2 at an applied potential of 0.20 V vs [Cp2Fe]+/0 at -20 °C in controlled-potential electrolysis, with a Faradaic efficiency of 75 %. Based on computational results, the catalyst undergoes sequential oxidation and deprotonation steps to form [LFeIV(NH2)2]2+, and thereafter bimetallic coupling to form an N-N bond.
期刊介绍:
Angewandte Chemie, a journal of the German Chemical Society (GDCh), maintains a leading position among scholarly journals in general chemistry with an impressive Impact Factor of 16.6 (2022 Journal Citation Reports, Clarivate, 2023). Published weekly in a reader-friendly format, it features new articles almost every day. Established in 1887, Angewandte Chemie is a prominent chemistry journal, offering a dynamic blend of Review-type articles, Highlights, Communications, and Research Articles on a weekly basis, making it unique in the field.