Anionic α‐diimine cobalt complexes, such as [K(thf)1.5{(DippBIAN)Co(η4‐cod)}] (1; Dipp=2,6‐diisopropylphenyl, cod=1,5‐cyclooctadiene), catalyze the dehydrogenation of several amine‐boranes. Based on the excellent catalytic properties, an especially effective transfer hydrogenation protocol for challenging olefins, imines, and N‐heteroarenes was developed. NH3BH3 was used as a dihydrogen surrogate, which transferred up to two equivalents of H2 per NH3BH3. Detailed spectroscopic and mechanistic studies are presented, which document the rate determination by acidic protons in the amine‐borane.

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 [(Dipp BIAN)CoBr 2 ] and the cocatalyst LiEt 3 BH. 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.

Iron group catalysts constitute a promising alternative to well-established noble metal catalysts in reduction reactions. This review advocates the use of kinetic poisoning experiments to distinguish between homotopic and heterotopic mechanisms.