Amminelithium amidoborane Li(NH3)NH2BH3: A new coordination compound with favorable dehydrogenation characteristics

Abstract

The monoammoniate of lithium amidoborane, Li(NH3)NH 2BH3, was synthesized by treatment of LiNH 2BH3 with ammonia at room temperature. This compound exists in the amorphous state at room temperature, but at -20°C crystallizes in the orthorhombic space group Pbca with lattice parameters of a= 9.711(4), b = 8.7027(5), c = 7.1999(1) Å, and V= 608.51 Å3. The thermal decomposition behavior of this compound under argon and under ammonia was investigated. Through a series of experiments we have demonstrated that Li(NH3)NH2BH3 is able to absorb/desorb ammonia reversibly at room temperature. In the temperature range of 4070°C, this compound showed favorable dehydrogenation characteristics. Specifically, under ammonia this material was able to release 3.0equiv hydrogen (11.18 wt%) rapidly at 60°C, which represents a significant advantage over LiNH 2BH3. It has been found that the formation of the coordination bond between ammonia and Li+ in LiNH2BH3 plays a crucial role in promoting the combination of hydridic B-H bonds and protic N-H bonds, leading to dehydrogenation at low temperature. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.