The structure of the strongest bronsted acid:: The carborane acid H(CHB11Cl11)
The structure of the strongest bronsted acid:: The carborane acid H(CHB11Cl11)
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DOI：
10.1021/ja058581l
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发表时间：
2006-03-15
影响因子：
15
通讯作者：
Reed, CA
中科院分区：
文献类型：
--
作者：
Stoyanov, ES;Hoffmann, SP;Reed, CA
最强且最稳定的碳硼酸 H(CHB11Cl11) 在气相中具有单体结构。红外光谱显示 2357(br) 和 2066(br) cm-1 处有两个 νH−Cl 谱带，结合 DFT 计算，表明至少有两种异构体共存。酸性质子通过不对称的 Cl−H…Cl 氢键桥接相邻的氯原子。 12,7异构体比7,8异构体更稳定。这些单体可以缩合成无定形固相，但具有亚稳态。它们很快衰变，首先变成无定形二聚体结构，然后变成通过 X 射线晶体学表征的结晶聚合物相。在聚合结构中，酸性质子桥接直链中碳硼烷阴离子 7−11 位的氯原子。二聚相（νCl−H···Cl = 1100−2200 cm-1）和聚合相（νasClHCl 约1100 cm-1，v 宽）具有更接近对称的低势垒氢键。这些发现对酸强度对相的依赖性具有影响。
The strongest and most robust carborane acid, H(CHB11Cl11), has a monomeric structure in the gas phase. IR spectra show two νH−Cl bands at 2357(br) and 2066(br) cm-1which, together with DFT calculations, indicate the coexistence of at least two isomers. The acidic proton bridges adjacent chlorine atoms with asymmetric Cl−H···Cl hydrogen bonding. The 12,7 isomer is more stable than the 7,8 isomer. These monomers can be condensed into an amorphous solid phase but are metastable. They quickly decay, first to an amorphous dimeric structure, then to a crystalline polymeric phase that has been characterized by X-ray crystallography. In the polymeric structure, the acidic proton bridges chlorine atoms from the 7−11 positions of carborane anions in linear chains. The dimeric phase (νCl−H···Cl = 1100−2200 cm-1) and polymeric phase (νasClHCl ca. 1100 cm-1, v broad) have more nearly symmetrical, low-barrier H-bonding. These findings have implications for the dependency of acid strength upon phase.