Amine-Borane Dehydrogenation and Transfer Hydrogenation Catalyzed by α-Diimine Cobaltates

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.