Amine–borane dehydrogenation chemistry: Metal-free hydrogen transfer, new catalysts and mechanisms, and the synthesis of polyaminoboranes

Over the past decade it has been shown that amine–boranes RR′R″N·BH3 (R, R′, R″ = H, alkyl, aryl) undergo efficient catalytic dehydrocoupling/dehydrogenation using transition metal or main group precatalysts to produce various classes of products including aminoboranes, borazanes, borazines, and, most recently, the first examples of soluble high molecular weight polyaminoboranes. Furthermore, related studies have also demonstrated that amine–boranes can act as hydrogen sources in metal-catalyzed or metal-free transfer hydrogenation reactions of unsaturated organic species, including imines and polar olefins. Our group has shown that metal-free hydrogen exchange reactions are also possible between amine–boranes and aminoboranes under mild conditions. This review provides an overview of our recent work in each of these areas.

Graphical abstractRecent contributions to the area of amine–borane chemistry from our group as well as others are described. Hydrogen transfer between amine–boranes and aminoboranes, catalytic mechanisms for the dehydrocoupling/dehydrogenation of amine–boranes and preparation of the first soluble polyaminoboranes are discussed.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Hydrogen transfer between amine–boranes and aminoboranes. ► Catalytic mechanisms for the dehydrocoupling/dehydrogenation of amine–boranes. ► Preparation of polyaminoboranes via dehydropolymerization of primary amine–boranes.