Catalytic hydrogenation using molecular hydrogen represents a green and practical approach for reductions of all kinds of organic chemicals. Traditionally, in the majority of these processes the presence of transition metal catalysts is required. In this regard, noble-metal-based catalysts have largely been implemented, such as the application of iridium, palladium, rhodium, ruthenium, and others. Recently, the employment of earth-abundant 3d metals has emerged to replace the utilization of scarce noble metals because of their availability, lower cost, and often reduced toxicity. In this respect, several cobalt complexes, in the form of either molecularly well-defined or in situ-formed complexes, are receiving increasing attention from the scientific community. Importantly, the stability and reactivity of the complexes have greatly been supported by multidentate ligands under steric and/or electronic influences. For instance, tridentate or tetradentate phosphine ligands indirectly tune the reactivity of the metal center to accelerate the overall process, whereas direct participation of the ligand in pincer-type complexes through ligand–metal cooperation regulates the elementary steps in the catalytic cycle.

中文翻译：

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钴配合物作为一类新兴的均相加氢催化剂

使用分子氢的催化加氢代表了一种绿色且实用的还原各种有机化学物质的方法。传统上，在这些方法的大多数中，需要过渡金属催化剂的存在。在这方面，已经大量实施了基于贵金属的催化剂，例如铱，钯，铑，钌等的应用。近来，由于它们的可用性，较低的成本以及通常降低的毒性，已经出现了使用富含地球的3d金属来替代稀有贵金属的利用。在这方面，以分子定义明确或原位形成的复合物形式存在的几种钴复合物受到了科学界的越来越多的关注。重要的，在空间和/或电子影响下，多齿配体极大地支持了配合物的稳定性和反应性。例如，三齿或四齿膦配体间接调节金属中心的反应性，从而加速整个过程，而配体通过配体-金属的配合直接参与钳型配合物，从而调节了催化循环中的基本步骤。