Del Castillo Trevor J, Thompson Niklas B, Suess Daniel L M, Ung Gaël, Peters Jonas C
Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.
Inorg Chem. 2015 Oct 5;54(19):9256-62. doi: 10.1021/acs.inorgchem.5b00645. Epub 2015 May 22.
Well-defined molecular catalysts for the reduction of N2 to NH3 with protons and electrons remain very rare despite decades of interest and are currently limited to systems featuring molybdenum or iron. This report details the synthesis of a molecular cobalt complex that generates superstoichiometric yields of NH3 (>200% NH3 per Co-N2 precursor) via the direct reduction of N2 with protons and electrons. While the NH3 yields reported herein are modest by comparison to those of previously described iron and molybdenum systems, they intimate that other metals are likely to be viable as molecular N2 reduction catalysts. Additionally, a comparison of the featured tris(phosphine)borane Co-N2 complex with structurally related Co-N2 and Fe-N2 species shows how remarkably sensitive the N2 reduction performance of potential precatalysts is. These studies enable consideration of the structural and electronic effects that are likely relevant to N2 conversion activity, including the π basicity, charge state, and geometric flexibility.
尽管数十年来人们一直对此感兴趣，但用于将N₂与质子和电子还原为NH₃的明确定义的分子催化剂仍然非常罕见，目前仅限于以钼或铁为特征的体系。本报告详细介绍了一种分子钴配合物的合成，该配合物通过用质子和电子直接还原N₂产生超化学计量产率的NH₃（每Co-N₂前体>200%的NH₃）。虽然本文报道的NH₃产率与先前描述的铁和钼体系相比并不高，但它们表明其他金属很可能作为分子N₂还原催化剂是可行的。此外，将特色的三（膦）硼烷Co-N₂配合物与结构相关的Co-N₂和Fe-N₂物种进行比较，显示了潜在预催化剂的N₂还原性能是多么显著地敏感。这些研究使得能够考虑可能与N₂转化活性相关的结构和电子效应，包括π碱性、电荷状态和几何灵活性。
