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Abstract：
Tetramethylphosphonium borohydride was synthesized via an ion metathesis reaction in a weakly-coordinating aprotic environment. [(CH3)4P]BH4, in contrast to related [(CH3)4N]+ compounds which tend to crystallize in a tetragonal system, adopts the distorted wurtzite structure (P63mc), resembling some salts containing analogous ions of As and Sb. [(CH3)4P]BH4 decomposes thermally in several endo- and exothermic steps above ca. 240 °C. This renders it more stable than [(CH3)4N]BH4, with a lowered temperature of decomposition onset by ca. 20 °C and solely exothermic processes observed. Raman spectra measured at the 0-10 GPa range indicate that a polymorphic transition occurs within 0.53-1.86 GPa, which is further confirmed by the periodic DFT calculations. The latter suggests a phase transition around 0.8 GPa to a high-pressure phase of [(CH3)4N]BH4. The P63mc phase seems to be destabilized under high pressure by relatively closer dihydrogen interactions, including the C-H…H-C contacts.
摘要：
在弱配位非质子环境中通过离子复分解反应合成了四甲基硼氢化物。[（CH3）4P]BH4，与倾向于在四方晶系中结晶的相关[（CH3）4N]化合物相反，采用扭曲的纤锌矿结构（P63mc），类似于一些含有类似As和Sb离子的盐。[(CH3)4P]BH4在上述几个吸热和放热步骤中热分解。240°C。这使得它比[(CH3)4N]BH4更稳定,分解起始温度降低了约1。20°C和单独观察到的放热过程。在0-10GPa范围内测得的拉曼光谱表明，在0.53-1.86GPa内发生了多态转变，这由周期性DFT计算进一步证实。后者表明约0.8GPa的相变为[（CH3）4N]BH4的高压相。P63mc相似乎在高压下由于相对更紧密的二氢相互作用而不稳定，包括C-H...H-C触点.
