Dehydrocoupling of Ammonia/Amine Boranes and Related Transformations Catalysed by Group 4 Metal Complexes

Abstract

Ammonia borane and amine boranes are main group analogues of alkanes, which are characterised by their large gravimetric hydrogen content. This hydrogen can be released in dehydrocoupling and dehydropolymerisation reactions to obtain B-N oligomers and polymers that are of importance as precursors for functional B-N materials. Furthermore, amine boranes are potent reagents for application in transfer hydrogenation reactions, representing a versatile, easy-to-handle alternative to the use of gaseous hydrogen for the reduction of organic compounds. Compared to late transition metals, complexes of readily available and comparatively inexpensive electropositive group 4 metals have been used to a much lesser extent. This review summarises the developments in the field of dehydrocoupling of amine boranes and transfer hydrogenation with these reagents, catalysed by complexes of group 4 metals. We analyse the background for these developments using examples and reaction mechanisms and provide an outlook for future developments in this field of research.

Keywords: Amine boranes; Hydrogen; Titanium; Transfer hydrogenation; Zirconium.