Anionic α-diimine cobalt complexes, such as [K(thf) 1.5 {( Dipp BIAN)Co(η 4 -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. NH 3 BH 3 was used as a dihydrogen surrogate, which transferred up to two equivalents of H 2 per NH 3 BH 3 . Detailed spectroscopic and mechanistic studies are presented, which document the rate determination by acidic protons in the amine-borane.