Tomich Anton W, Proctor Stephen, Yang Moon Young, Chen Jianjun, Zhao Yifan, Chen Edward, Das Tridip, Merinov Boris V, Goddard William A, Guo Juchen, Lavallo Vincent
Department of Chemistry, University of California Riverside, Riverside, California 92521, United States.
Materials and Process Simulations Center, California Institute of Technology Pasadena, California 91125, United States.
ACS Cent Sci. 2025 Apr 23;11(5):734-741. doi: 10.1021/acscentsci.5c00043. eCollection 2025 May 28.
Borohydrides are important molecular entities for a myriad of applications from organic synthesis to components of functional materials and devices. All borohydrides have been thought to be susceptible to spontaneous ignition when exposed to a flame. Herein we demonstrate that this is not always true by identifying several borohydride rich materials that are resistant to combustion when contacted with a torch. One of these materials is a Li salt of a carborane anion that depending on its coordination environment exists as a unique ionic liquid that has a nearly naked Li countercation. This has provided us with the first opportunity to spectroscopically probe the interactions of such carborane anions with Li metal in a solvent free environment. We found that this carborane anion is immune to deleterious reduction at Li-metal surfaces, as evidenced by XPS, EDS and SEM analysis of the Li-Metal surface after exposure to the ionic liquid. Additionally, NMR analysis of the ionic liquid after stirring it with Li powder shows no reaction. Calculations show that the cage skeleton is reduced at the surface monolayer, but as the reduced form is removed from contact with Li-metal, the cage reverts to the -form, demonstrating reversibility.
硼氢化物是一类重要的分子实体，在从有机合成到功能材料及器件组件等众多应用中都有重要作用。一直以来，人们认为所有硼氢化物在接触火焰时都易于自燃。在此，我们通过鉴定几种富含硼氢化物的材料来证明情况并非总是如此，这些材料在用火炬接触时具有抗燃烧性。其中一种材料是碳硼烷阴离子的锂盐，根据其配位环境，它以一种独特的离子液体形式存在，其中锂反阳离子几乎是裸露的。这为我们提供了首个在无溶剂环境下通过光谱探测此类碳硼烷阴离子与锂金属相互作用的机会。我们发现，这种碳硼烷阴离子在锂金属表面不会发生有害还原反应，这通过对接触离子液体后的锂金属表面进行XPS、EDS和SEM分析得到了证实。此外，将离子液体与锂粉搅拌后进行的NMR分析表明没有反应发生。计算结果表明，笼状骨架在表面单分子层发生了还原，但由于还原后的形式不再与锂金属接触，笼状结构又恢复到原来的形式，这证明了其可逆性。
