Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States.
J Am Chem Soc. 2019 Jun 12;141(23):9106-9123. doi: 10.1021/jacs.9b03337. Epub 2019 May 28.
Homogeneous catalysis with Earth-abundant, first-row transition metals, including iron and cobalt, has gained considerable recent attention as a potentially cost-effective and sustainable alternative to more commonly and historically used precious metals. Because fundamental organometallic transformations, such as oxidative addition and reductive elimination, are two-electron processes and essential steps in many important catalytic cycles, controlling redox chemistry-in particular overcoming one-electron chemistry-has been as a central challenge with Earth-abundant metals. This Perspective focuses on approaches to impart sufficiently strong ligand fields to generate electron-rich metal complexes able to promote oxidative addition reactions where the redox changes are exclusively metal-based. Emphasis is placed on how ligand design and exploration of fundamental organometallic chemistry coupled with mechanistic understanding have been used to discover iron catalysts for the hydrogen isotope exchange in pharmaceuticals and cobalt catalysts for C(sp)-H borylation reactions. A pervasive theme is that first-row metal complexes often promote unique chemistry from their precious-metal counterparts, demonstrating that these elements offer a host of new opportunities for reaction discovery and for more sustainable catalysis.
富含地球元素的第一过渡金属（包括铁和钴）的均相催化，因其作为更常用和历史上更常用的贵金属的潜在成本效益和可持续替代品而受到相当大的关注。由于基本的有机金属转化，如氧化加成和还原消除，是两电子过程，并且是许多重要催化循环中的关键步骤，因此控制氧化还原化学 - 特别是克服单电子化学 - 一直是富含地球元素金属的核心挑战。本观点侧重于采用足够强的配体场来生成富电子金属配合物的方法，这些配合物能够促进氧化加成反应，其中氧化还原变化完全基于金属。重点介绍了如何通过配体设计和基础有机金属化学的探索以及对反应机理的理解，发现了用于药物中氢同位素交换的铁催化剂和用于 C(sp)-H 硼化反应的钴催化剂。一个普遍的主题是，第一过渡金属配合物通常会从贵金属配合物中促进独特的化学，这表明这些元素为反应发现和更可持续的催化提供了许多新机会。
