Zhang Jiji, Fu Xiaodu, Lin Zhenyang, Xie Zuowei
Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The Chinese University of Hong Kong , Shatin, New Territories, Hong Kong, China.
Inorg Chem. 2015 Feb 16;54(4):1965-73. doi: 10.1021/ic502866h. Epub 2015 Jan 26.
The synthesis, structure, spectroscopic characterization, and density functional theory (DFT) calculations of several 13-vertex carborane radical anions were described. Reactions of 13-vertex closo-carboranes with 1 equiv of finely cut sodium metal in tetrahydrofuran at room temperature afforded the corresponding sodium salts of carborane radical anions as dark-red crystals in very good yield. They represent a rare class of clusters having 2n + 3 framework electrons, which lie between the two well-established and abundant closed 2n + 2 (closo) and open 2n + 4 (nido) skeleton systems. However, attempts to prepare the 12- or 14-vertex analogues failed. DFT calculations indicate that the ΔGsol,1 - ΔGsol,2 values, the difference in the solvation-corrected free-energy changes between the first and second one-electron-reduction processes, can be used as a measure for the stability of carborane radical anions. The relatively high stability of 13-vertex carborane radical anions is related to the unique structures of 13-vertex carboranes, which give rise to minimal structure disruption upon the first one-electron reduction.
描述了几种13顶点碳硼烷自由基阴离子的合成、结构、光谱表征及密度泛函理论（DFT）计算。13顶点闭式碳硼烷在室温下于四氢呋喃中与1当量细切的金属钠反应，以非常高的产率得到相应的碳硼烷自由基阴离子的钠盐，呈深红色晶体。它们代表了一类罕见的具有2n + 3骨架电子的簇合物，介于两个已确立且丰富的封闭2n + 2（闭式）和开放2n + 4（巢式）骨架体系之间。然而，制备12或14顶点类似物的尝试失败了。DFT计算表明，ΔGsol,1 - ΔGsol,2值，即第一个和第二个单电子还原过程之间溶剂化校正自由能变化的差异，可作为碳硼烷自由基阴离子稳定性的一种度量。13顶点碳硼烷自由基阴离子相对较高的稳定性与13顶点碳硼烷的独特结构有关，这种结构在第一次单电子还原时导致的结构破坏最小。
