Elucidating electron-transfer events in polypyridine nickel complexes for reductive coupling reactions
Elucidating electron-transfer events in polypyridine nickel complexes for reductive coupling reactions
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DOI：
10.1038/s41929-023-00925-4
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发表时间：
2023-03-09
期刊：
影响因子：
37.8
通讯作者：
Martin, Ruben
中科院分区：
文献类型：
--
作者：
Day, Craig S. S.;Renteria-Gomez, Angel;Martin, Ruben
聚吡啶配位镍配合物广泛用作各种交叉偶联反应中的特殊催化剂。这些配合物的快速采用暂时归因于它们在不同氧化态之间穿梭并参与电子转移反应的能力。然而，人们对这些反应的机理了解甚少。在这里，我们研究了含有聚吡啶配体的拟卤化物和卤化物连接的 Ni(II) 配合物在电子转移反应中的反应性。具体而言，Ni(II) 卤化物配合物在生成 Ni(I)L-n 物质的过程中非常容易地触发与 Ni(0) 的歧化，而相应的 Ni(II) 拟卤化物同系物对电子转移具有抵抗力，而 Ni(I) 拟卤化物易于发生歧化事件。这些观察结果得到了电化学技术和详细量子力学计算的证实。我们还表明，催化失活的 Ni(II) 拟卤化物络合物可以在外源盐存在的情况下重新活化。从更广泛的角度来看，这项研究为镍催化交叉偶联领域中被忽视的基本步骤提供了合理化，从而为设计未来的镍催化反应提供了蓝图。
Polypyridine-ligated nickel complexes are widely used as privileged catalysts in a variety of cross-coupling reactions. The rapid adoption of these complexes is tentatively attributed to their ability to shuttle between different oxidation states and engage in electron-transfer reactions. However, these reactions are poorly understood in mechanistic terms. Here we investigate the reactivity of pseudohalide- and halide-ligated Ni(II) complexes, containing polypyridine ligands, in electron-transfer reactions. Specifically, Ni(II) halide complexes trigger comproportionation with Ni(0) with exceptional ease en route to Ni(I)L-n species, whereas the corresponding Ni(II) pseudohalide congeners are resistant to electron transfer, with Ni(I) pseudohalides being prone to disproportionation events. These observations are corroborated by electrochemical techniques and detailed quantum mechanical calculations. We also show that catalytically inactive Ni(II) pseudohalide complexes can be reactivated in the presence of exogeneous salts. From a broader perspective, this study provides rationalizations for overlooked and fundamental steps within the Ni-catalysed cross-coupling arena, thus offering blueprints for designing future Ni-catalysed reactions.