The reaction of 1,8-bis(dimethylamino)naphthalene—which is often referred by the trade name Proton-Sponge (PS)—with decaborane in hexane afforded [HPS][B₁₀H₁₃] (1) salt as a pale-yellow precipitate. Variable-temperature NMR studies allowed the full assignment of ¹H and ¹¹B spectra for this familiar ten-vertex polyhedral anion. In addition, this work reveals that an increase in the temperature leads to the intramolecular exchange of three B–H–B hydrogen atoms around the hexagonal face of the boat-shaped cluster. This previously unrecognised H-tautomerism complements the long-known low-energy proton exchange of only one of the bridging hydrogen atoms. The temperature dependent proton fluxional behaviour controls the molecular environment of the polyhedral cage, averaging the negative charge of the anion. The result is a debilitation of the cation–anion interactions in solution, favouring the transfer of the proton from the organic aromatic cation, [HPS]⁺, to the polyhedral anion, [B₁₀H₁₃]⁻. This proton transfer affords Proton-Sponge and decaborane, increasing the entropy of the system and sustaining an equilibrium which at high temperatures shifts toward the neutral reactants and at low temperatures moves toward the ionic products. A single X-ray diffraction analysis of 1 is discussed.

中文翻译：

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十硼烷阴离子互变异构：离子对和质子转移控制†

1,8-双（二​​甲基氨基）萘（通常以商品名Proton-Sponge（PS）命名）与十硼烷在己烷中的反应得到浅色[HPS] [B ₁₀ H ₁₃ ]（1）盐，黄色沉淀。可变温度NMR研究允许¹ H和¹¹的完全分配该熟悉的十顶点多面体阴离子的B光谱。此外，这项工作表明，温度升高导致船形簇六边形表面周围的三个B–H–B氢原子发生分子内交换。这种以前无法识别的H-互变异构现象补充了桥接氢原子中只有一个的长期已知的低能质子交换。温度依赖的质子通量行为控制多面体笼的分子环境，平均阴离子的负电荷。结果导致溶液中阳离子与阴离子的相互作用减弱，有利于质子从有机芳族阳离子[HPS] ⁺转移到多面体阴离子[B ₁₀ H ₁₃ ] ^-。这种质子转移提供了质子海绵和十硼烷，增加了系统的熵并维持了平衡，该平衡在高温下向中性反应物移动，在低温下向离子产物移动。讨论了1的单X射线衍射分析。