The (C₆₀CN)⁻ formed by the reaction of CN⁻ with fullerene shows high electron rich character, very similar to C₆₀˙⁻, and it behaves as a large anion. Similar to Cp⁻, the bulky anion, (C₆₀CN)⁻, acts as a strong η⁵ ligand towards transition metal centers. Previous studies on η⁵ coordination of fullerene cage are reported for pseudo fullerenes whereas the present study deals with sandwich complexes of (C₆₀CN)⁻ with Fe(II), Ru(II), Cr(II), Mo(II), and Ni(II) and multi-decker sandwich complexes of CN–fullerides with Fe(II). The structural parameters of these complexes and the corresponding Cp⁻ complexes showed very close resemblance. Analysis of the metal-to-carbon bonding molecular orbitals showed that sandwich complex [Fe(η⁵-(C₆₀CN)⁻)₂] exhibit bonding features very similar to that of ferrocene. Also, a 6-fold decrease in the band gap energy is observed for [Fe(η⁵-(C₆₀CN)⁻)₂] compared to ferrocene. The energy of dissociation (ΔE) of the ligand (C₆₀CN)⁻ from [Fe(η⁵-(C₆₀CN)⁻)₂] is slightly lower than the ΔE of a Cp* ligand from a ferrocene derivative wherein each cyclopentadienyl unit is substituted with four tertiary butyl groups. The (C₆₀CN)⁻ ligand behaved as one of the bulkiest ligands in the chemistry of sandwich complexes. Further, the coordinating ability of the dianion, (C₆₀(CN)₂)²⁻ is evaluated which showed strong coordination ability simultaneously with two metal centers leading to the formation of multi-decker sandwich and pearl-necklace type polymeric structures.

中文翻译：

---

富勒烯金属 η5 三明治和多层三明治复合物：DFT 预测

^{CN −}与富勒烯反应形成的(C ₆₀ CN) ^{−具有高富电子特性，与C} ₆₀ ˙ ⁻非常相似，表现为大阴离子。与 Cp ^-类似，大体积阴离子 (C ₆₀ CN) ^-充当过渡金属中心的强 η ^5配体。以前关于伪富勒烯的富勒烯笼的 η ⁵配位的研究报道了，而本研究涉及 (C ₆₀ CN)的三明治复合物^-与 Fe(II)、Ru(II)、Cr(II)、Mo(II) 和 Ni(II) 以及 CN-富勒烯与 Fe(II) 的多层三明治复合物。这些配合物的结构参数和相应的 Cp ^-配合物表现出非常相似。金属-碳键合分子轨道分析表明，三明治络合物[Fe(η ⁵ -(C ₆₀ CN) ⁻ ) ₂ ] 表现出与二茂铁非常相似的键合特征。此外，与二茂铁相比，[Fe(η ⁵ -(C ₆₀ CN) ^- ) ₂ ]的带隙能量降低了 6 倍。配体 (C ₆₀ CN)的解离能 (Δ E )^-来自[Fe(η ⁵ -(C ₆₀ CN) ^- ) ₂ ] 略低于来自二茂铁衍生物的Cp*配体的Δ E，其中每个环戊二烯基单元被四个叔丁基取代。(C ₆₀ CN) ^-配体在三明治复合物化学中表现为最大的配体之一。此外，评估了二价阴离子 (C ₆₀ (CN) ₂ ) ²⁻的配位能力，它显示出同时与两个金属中心的强配位能力，从而导致形成多层三明治和珍珠项链型聚合物结构。