Cobalt-Catalyzed Hydrogenations via Olefin Cobaltate and Hydride Intermediates

Redox noninnocent ligands are a promising tool to moderate electron transfer processes within base-metal catalysts. This report introduces bis­(imino)­acenaphthene (BIAN) cobaltate complexes as hydrogenation catalysts. Sterically hindered trisubstituted alkenes, imines, and quinolines underwent clean hydrogenation under mild conditions (2–10 bar, 20–80 °C) by use of the stable catalyst precursor [(DippBIAN)­CoBr2] and the cocatalyst LiEt3BH. Mechanistic studies support a homogeneous catalysis pathway involving alkene and hydrido cobaltates as active catalyst species. Furthermore, considerable reaction acceleration by alkali cations and Lewis acids was observed. The dinuclear hydridocobaltate anion with bridging hydride ligands was isolated and fully characterized.

氧化还原非无辜配体（redox noninnocent ligands）是调控贱金属催化剂内电子转移过程的极具潜力的工具。本工作报道了双(亚胺)苊（bis(imino)acenaphthene，BIAN）钴酸根配合物作为氢化催化剂的应用。以稳定的催化剂前驱体[(DippBIAN)CoBr₂]与助催化剂三乙基硼氢化锂（LiEt3BH）为试剂，位阻型三取代烯烃、亚胺及喹啉类化合物可在温和条件（2~10巴、20~80℃）下顺利发生高选择性氢化反应。机理研究证实该反应遵循均相催化路径，其活性催化物种为烯烃配位钴酸根与氢合钴酸根配合物。此外，研究还观察到碱金属阳离子与路易斯酸可显著加速反应进程。研究人员分离得到了带有桥联氢配体的双核氢合钴酸根阴离子，并对其完成了全面表征。