Arora Vinay, Narjinari Himani, Nandi Pran Gobinda, Kumar Akshai
Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
Dalton Trans. 2021 Mar 16;50(10):3394-3428. doi: 10.1039/d0dt03593a.
Organometallic catalysts have played a key role in accomplishing numerous synthetically valuable organic transformations that are either otherwise not possible or inefficient. The use of precious, sparse and toxic 4d and 5d metals are an apparent downside of several such catalytic systems despite their immense success over the last several decades. The use of complexes containing Earth-abundant, inexpensive and less hazardous 3d metals, such as nickel, as catalysts for organic transformations has been an emerging field in recent times. In particular, the versatile nature of the corresponding pincer-metal complexes, which offers great control of their reactivity via countless variations, has garnered great interest among organometallic chemists who are looking for greener and cheaper alternatives. In this context, the current review attempts to provide a glimpse of recent developments in the chemistry of pincer-nickel catalyzed reactions. Notably, there have been examples of pincer-nickel catalyzed reactions involving two electron changes via purely organometallic mechanisms that are strikingly similar to those observed with heavier Pd and Pt analogues. On the other hand, there have been distinct differences where the pincer-nickel complexes catalyze single-electron radical reactions. The applicability of pincer-nickel complexes in catalyzing cross-coupling reactions, oxidation reactions, (de)hydrogenation reactions, dehydrogenative coupling, hydrosilylation, hydroboration, C-H activation and carbon dioxide functionalization has been reviewed here from synthesis and mechanistic points of view. The flurry of global pincer-nickel related activities offer promising avenues in catalyzing synthetically valuable organic transformations.
有机金属催化剂在实现众多具有合成价值的有机转化过程中发挥了关键作用，这些转化在其他情况下要么无法实现，要么效率低下。尽管在过去几十年中取得了巨大成功，但使用珍贵、稀缺且有毒的4d和5d金属是几种此类催化体系的一个明显缺点。近年来，使用含有地壳中丰富、廉价且危害较小的3d金属（如镍）的配合物作为有机转化的催化剂已成为一个新兴领域。特别是，相应的钳形金属配合物具有多功能性，通过无数种变化能很好地控制其反应活性，这引起了寻求更绿色、更廉价替代物的有机金属化学家的极大兴趣。在此背景下，本综述试图简要介绍钳形镍催化反应化学的最新进展。值得注意的是，有一些钳形镍催化反应的例子，它们通过纯有机金属机制涉及两个电子的变化，这与较重的钯和铂类似物所观察到的情况惊人地相似。另一方面，在钳形镍配合物催化单电子自由基反应方面存在明显差异。本文从合成和机理的角度综述了钳形镍配合物在催化交叉偶联反应、氧化反应、（脱）氢化反应、脱氢偶联、硅氢化反应、硼氢化反应、C-H活化和二氧化碳官能化反应中的适用性。全球范围内与钳形镍相关的一系列活动为催化具有合成价值的有机转化提供了有前景的途径。
