Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China.
Inorg Chem. 2010 May 3;49(9):4319-23. doi: 10.1021/ic100308j.
A stepwise phase transition in the formation of lithium amidoborane via the solid-state reaction of lithium hydride and ammonia borane has been identified and investigated. Structural analyses reveal that a lithium amidoborane-ammonia borane complex (LiNH(2)BH(3).NH(3)BH(3)) and two allotropes of lithium amidoborane (denoted as alpha- and beta-LiNH(2)BH(3), both of which adopt orthorhombic symmetry) were formed in the process of synthesis. LiNH(2)BH(3).NH(3)BH(3) is the intermediate of the synthesis and adopts a monoclinic structure that features layered LiNH(2)BH(3) and NH(3)BH(3) molecules and contains both ionic and dihydrogen bonds. Unlike alpha-LiNH(2)BH(3), the units of the beta phase have two distinct Li(+) and NH(2)BH(3) environments. beta-LiNH(2)BH(3) can only be observed in energetic ball milling and transforms to alpha-LiNH(2)BH(3) upon extended milling. Both allotropes of LiNH(2)BH(3) exhibit similar thermal decomposition behavior, with 10.8 wt % H(2) released when heated to 180 degrees C; in contrast, LiNH(2)BH(3).NH(3)BH(3) releases approximately 14.3 wt % H(2) under the same conditions.
通过氢化锂和氨硼烷的固态反应，已经确定并研究了锂氨硼烷形成中的逐步相转变。结构分析表明，在合成过程中形成了锂氨硼烷-氨硼烷复合物（LiNH(2)BH(3).NH(3)BH(3））和两种锂氨硼烷的同素异形体（分别表示为α-和β-LiNH(2)BH(3），两者均采用正交对称）。LiNH(2)BH(3).NH(3)BH(3）是合成的中间体，采用层状 LiNH(2)BH(3）和 NH(3)BH(3）分子的单斜结构，并含有离子和双氢键。与α-LiNH(2)BH(3）不同，β相的单元具有两个不同的 Li(+)和NH(2)BH(3)环境。β-LiNH(2)BH(3）只能在高能球磨中观察到，并且在延长的球磨过程中转化为α-LiNH(2)BH(3）。两种 LiNH(2)BH(3）同素异形体都表现出相似的热分解行为，在加热到 180°C 时释放 10.8wt%的 H(2）；相比之下，LiNH(2)BH(3).NH(3)BH(3）在相同条件下释放约 14.3wt%的 H(2）。
