Abundant Metals Give Precious Hydrogenation Performance

Iron- or cobalt-based catalysts have outperformed traditional precious metal catalysts in several hydrogenation reactions. [Also see Reports by Jagadeesh et al. , Friedfeld et al. , and Zuo et al. ] Homogeneous catalysts based on precious metals have enabled highly selective synthesis of organic compounds. Precious metal catalysts including ruthenium (Ru), rhodium (Rh), and platinum (Pt) have been superstars of both homogeneous and heterogeneous catalysis. In recent years, increasing efforts have been devoted to the design and discovery of homogeneous catalysts that incorporate base metals, such as iron (Fe) and cobalt (Co) ( 1 – 3 ) (see the figure). Catalytic hydrogenations are one of the extraordinary success stories of homogeneous catalysis, and three reports in this issue describe remarkable progress in the use of Earth-abundant metals as catalysts for hydrogenations. Hydrogenations are conceptually simple—H 2 is added across a C=C or C=O double bond—but mechanistic studies have revealed considerable complexity with respect to how the metal catalyzes hydrogenations ( 4 ). On page 1080, Zuo et al. ( 5 ) report iron catalysts for asymmetric hydrogenation of C=O bonds. On page 1076, cobalt catalysts for asymmetric hydrogenation of C=C bonds are described by Friedfeld et al. ( 6 ). On page 1073, Jagadeesh et al. ( 7 ) report on nanoscale iron catalysts for synthesis of functionalized anilines through hydrogenation of nitroarenes.