Copper(II)‐Assisted Ammonia Borane Dehydrogenation: An Insight

Abstract

Amine boranes are in limelight in recent times as they have been considered as one of the potential candidates for onboard hydrogen storage. Among various amine boranes, Ammonia borane (AB, 19.6 wt % H) with hydridic (BÀ H) and protic (NÀ H) hydrogens on adjacent atoms is the most studied molecule. From the past decade, as the chemists try to develop effective catalysts for the release of hydrogen from AB, simultaneously new interesting chemistry of AB has been evolved. These studies increased the scope of AB for other applications such as in the synthesis of nanoparticles, as transfer hydrogenation agent, in organic synthesis, etc. Here we focus on Cu 2 + -AB system in water and organic solvents (THF/diglyme) to unveil new chemistry. CuCl 2 readily reacted with AB in both media to generate H 2 and Cu 2 + was reduced to Cu(0) when AB is present in excess. We got an insight into these reactions by carrying out reactions for various Cu 2 + /AB mole ratios and characterizing the reaction mixtures with 11 B NMR spectroscopy. The copper products were identified by powder X-ray diffraction technique. We noticed the formation of CuH and CuCl intermediates upon BÀ H bond scission by Cu 2 + .