Stepwise Phase Transition in the Formation of Lithium Amidoborane

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• 作者：Chengzhang Wu ; Guotao Wu ; Zhitao Xiong ; William I. F. David ; Kate R. Ryan ; Martin O. Jones ; Peter P. Edwards ; Hailiang Chu ; Ping Chen
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：May 3, 2010
• 年：2010
• 卷：49
• 期：9
• 页码：4319-4323
• 全文大小：761K
• 年卷期：v.49,no.9(May 3, 2010)
• ISSN：1520-510X

文摘

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 (LiNH₂BH₃·NH₃BH₃) and two allotropes of lithium amidoborane (denoted as α- and β-LiNH₂BH₃, both of which adopt orthorhombic symmetry) were formed in the process of synthesis. LiNH₂BH₃·NH₃BH₃ is the intermediate of the synthesis and adopts a monoclinic structure that features layered LiNH₂BH₃ and NH₃BH₃ molecules and contains both ionic and dihydrogen bonds. Unlike α-LiNH₂BH₃, the units of the β phase have two distinct Li⁺ and [NH₂BH₃]⁻ environments. β-LiNH₂BH₃ can only be observed in energetic ball milling and transforms to α-LiNH₂BH₃ upon extended milling. Both allotropes of LiNH₂BH₃ exhibit similar thermal decomposition behavior, with 10.8 wt % H₂ released when heated to 180 °C; in contrast, LiNH₂BH₃·NH₃BH₃ releases approximately 14.3 wt % H₂ under the same conditions.