Sustainable metal catalysis with iron: From rust to a rising star?
Sustainable metal catalysis with iron: From rust to a rising star?
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DOI：
10.1002/anie.200800012
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Beller, Matthias
中科院分区：
文献类型：
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作者：
Enthaler, Stephan;Junge, Kathrin;Beller, Matthias
发展可持续的、更有效的和选择性的有机合成是化学的基本研究目标之一。在这方面，催化是一项关键技术，因为在工业规模上，大约80%的所有化学和制药产品都是由催化剂制成的，在现代工艺中甚至更多。90%）。特别是，有机金属化合物已成为精细和散装化学品的既定合成工具，并且数百种分子，定义的前催化剂可供世界各地的化学家购买。活性催化剂的反应性和选择性受到中心金属的选择和周围配体的设计的广泛影响。在过去的几十年中，多种过渡金属催化剂，特别是基于贵金属如钯、铑、铱和钌的催化剂，已被证明对于大量应用是有效的。然而，这些金属的有限可用性以及它们的高价格（图1）和显著的毒性使得人们希望寻找更经济和环境友好的替代品。该问题的一个可能的解决方案是增加使用基于第一行过渡金属如铁、铜、锌和锰的催化剂。与贵金属相比，铁尤其具有显著的优势，因为它是地壳中第二丰富的金属（4.7重量%）。各种铁盐和铁络合物可大规模商购获得或易于合成。此外，铁化合物相对无毒。与人造贵金属催化剂不同，铁作为重要的关键元素参与各种生物系统，例如，在金属蛋白中用于运输或代谢小分子（氧，氮，甲烷等）。和电子转移反应（图2）。由于氧化态的容易变化和独特的刘易斯酸特性，铁催化剂原则上允许广泛的合成转化，例如加成、取代、环加成、氢化、还原、氧化、偶联反应、异构化、重排和聚合。然而，大多数已知的与铁的催化反应要么范围有限，要么不符合实际应用。在这方面，铁作为催化剂的使用迄今为止还不发达。2004年，Bolm埃塔尔发表了一篇精彩的评论文章。他总结了当时铁催化的成就。[1]从那时起，许多令人印象深刻的例子证明了铁催化剂在还原，氧化和偶联化学领域的潜力增加，这是工业用途最有前途的反应。在此，我们希望强调选定的结果，并提出一个问题，铁是否会成为催化工具箱中的一颗新的星星？
The development of sustainable, more efficient, and selective organic synthesis is one of the fundamental research goals in chemistry. In this respect, catalysis is a key technology, since approximately 80% of all chemical and pharmaceutical products on an industrial scale are made by catalysts—even more in the case of modern processes (ca. 90%). In particular, organometallic compounds have become an established synthetic tool for both fine and bulk chemicals and several hundreds of molecular, defined pre-catalysts are commercially available for chemists around the world. The reactivity and selectivity of the active catalyst are widely influenced by the choice of the central metal and by the design of surrounded ligands. During the last decades, manifold transition-metal catalysts especially based on precious metals such as palladium, rhodium, iridium, and ruthenium have been proven to be efficient for a large number of applications. However, the limited availability of these metals as well as their high price (Figure 1) and significant toxicity makes it desirable to search for more economical and environmentally friendly alternatives. A possible solution of this problem could be the increased use of catalysts based on first row transition metals, such as iron, copper, zinc, and manganese. Especially iron offers significant advantages compared with precious metals, since it is the second most abundant metal in the earth crust (4.7 wt%). Various iron salts and iron complexes are commercially accessible on a large scale or easy to synthesize. Furthermore, iron compounds are relatively nontoxic. In contrast to man-made precious-metal catalysts, iron takes part in various biological systems as essential key element, for example, in metalloproteins for the transport or metabolism of small molecules (oxygen, nitrogen, methane, etc.) and electron-transfer reactions (Figure 2). Thanks to the facile change of oxidation state and the distinct Lewis acid character, iron catalysts allow in principle a broad range of synthetic transformations, for example, additions, substitutions, cycloadditions, hydrogenations, reductions, oxidations, coupling reactions, isomerizations, rearrangements, and polymerizations. However, most of the known catalytic reactions with iron are either limited in scope or do not qualify for practical applications. In this respect the use of iron as catalyst is so far underdeveloped.In 2004, an excellent review article by Bolm etal. summarized the achievements in iron catalysis until that time.[1] Since then, a number of impressive examples demonstrated the increased potential of iron catalysts in the field of reduction, oxidation, and coupling chemistry, which are the most promising reactions for industrial purposes. Herein, we wish to emphasize selected results and raise the question whether iron will be a new star in the catalysis tool box?