Stepwise phase transition in the formation of lithium amidoborane.
Stepwise phase transition in the formation of lithium amidoborane.
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DOI：
10.1021/ic100308j
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发表时间：
2010-05
影响因子：
4.6
通讯作者：
Chengzhang Wu;Guotao Wu;Zhitao Xiong;W. David;K. R. Ryan;M. Jones;P. Edwards;H. Chu;Ping Chen
中科院分区：
文献类型：
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作者：
Chengzhang Wu;Guotao Wu;Zhitao Xiong;W. David;K. R. Ryan;M. Jones;P. Edwards;H. Chu;Ping Chen
研究了氢化锂与氨硼烷固相反应生成氨基硼烷锂的阶段性相变。结构分析表明，在合成过程中形成了氨基硼烷锂-氨硼烷配合物（LiNH（2）BH（3）.NH（3）BH（3））和氨基硼烷锂的两种同素异形体（记为α-和β-LiNH（2）BH（3），均为正交对称）。LiNH（2）BH（3）.NH（3）BH（3）是合成的中间体，并采用单斜结构，其特征在于层状LiNH（2）BH（3）和NH（3）BH（3）分子，并含有离子键和氢键。与α-LiNH（2）BH（3）不同，β相的单元具有两种不同的Li（+）和[NH（2）BH（3）]（-）环境。β-LiNH（2）BH（3）只能在高能球磨中观察到，并在延长球磨时转化为α-LiNH（2）BH（3）。LiNH（2）BH（3）的两种同素异形体表现出相似的热分解行为，当加热到180 ℃时释放10.8重量%的H（2）;相反，LiNH（2）BH（3）.NH（3）BH（3）在相同条件下释放约14.3重量%的H（2）。
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.