In this paper, we present a comparative study of the redox properties of the icosahedral [Rh₁₂E(CO)₂₇]ⁿ⁻ (n = 4 when E = Ge or Sn and n = 3 when E = Sb or Bi) family of clusters through in situ infrared spectroelectrochemistry experiments and density functional theory computational studies. These clusters show shared characteristics in terms of molecular structure, being all E-centered icosahedral species, and electron counting, possessing 170 valence electrons as predicted by the electron-counting rules, based on the cluster-borane analogy, for compounds with such metal geometry. However, in some cases, clusters of similar nuclearity, and beyond, may show multivalence behavior and may be stable with a different electron counting, at least on the time scale of the electrochemical analyses. The experimental results, confirmed by theoretical calculations, showed a remarkable electron-sponge behavior for [Rh₁₂Ge(CO)₂₇]⁴⁻ (1), [Rh₁₂Sb(CO)₂₇]³⁻ (3), and [Rh₁₂Bi(CO)₂₇]³⁻ (4), with a cluster charge going from −2 to −6 for 1 and 3 and from −2 to −7 for cluster 4, making them examples of molecular electron reservoirs. The [Rh₁₂Sn(CO)₂₇]⁴⁻ (2) derivative, conversely, presents a limited ability to exist in separable reduced cluster species, at least within the experimental conditions, while in the gas phase it appears to be stable both as a penta- and hexa-anion, therefore showing a similar redox activity as its congeners. As a fallout of those studies, during the preparation of [Rh₁₂Sb(CO)₂₇]³⁻, we were able to isolate a new species, namely, [Rh₁₁Sb(CO)₂₆]²⁻, which presents a Sb-centered nido-icosahedral metal structure possessing 158 cluster valence electrons, in perfect agreement with the polyhedral skeletal electron pair theory.

中文翻译：

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异金属铑簇作为电子库：中心二十面体 [Rh12E(CO)27]n-原子精确羰基化合物的化学、电化学和理论研究

在本文中，我们比较研究了二十面体 [Rh ₁₂ E(CO) ₂₇ ] ⁿ⁻（当 E = Ge 或 Sn 时 n = 4，当 E = Sb 或 Bi 时 n = 3）原位聚类红外光谱电化学实验和密度泛函理论计算研究。这些簇在分子结构方面显示出共同的特征，都是以 E 为中心的二十面体物种，电子计数具有 170 个价电子，根据电子计数规则预测，基于簇硼烷类比，对于具有这种金属几何形状的化合物. 然而，在某些情况下，类似核数的簇可能会表现出多价行为，并且在不同的电子计数下可能是稳定的，至少在电化学分析的时间尺度上是这样。由理论计算证实的实验结果表明，[Rh ₁₂ Ge(CO) ₂₇ ] ⁴⁻ ( 1)、[Rh ₁₂ Sb(CO) ₂₇ ] ³⁻ ( 3 ) 和 [Rh ₁₂ Bi(CO) ₂₇ ] ³⁻ ( 4 )，1和3的簇电荷从 -2 到 -6以及从-2 到 -7 为簇4，使它们成为分子电子库的例子。[Rh ₁₂ Sn(CO) ₂₇ ] ⁴⁻ ( 2) 衍生物，相反，在可分离的还原簇物种中存在的能力有限，至少在实验条件下，而在气相中，它作为五阴离子和六阴离子似乎都是稳定的，因此显示出类似的氧化还原活性作为其同类。作为这些研究的结果，在制备 [Rh ₁₂ Sb(CO) ₂₇ ] ^{3− 期间}，我们能够分离出一个新物种，即 [Rh ₁₁ Sb(CO) ₂₆ ] ²⁻，它呈现了一个 Sb -中心的nido-二十面体金属结构，具有158个簇价电子，与多面体骨架电子对理论完全一致。