Huang Ya-Shan, Xue Yuan, Muñoz-Castro Alvaro, Popov Ivan A, Sun Zhong-Ming
State Key Laboratory of Elemento-Organic Chemistry, Tianjin Key Lab for Rare Earth Materials and Applications, School of Materials Science and Engineering, Nankai University, Tianjin, 300350, P.R. China.
Department of Chemistry, The University of Akron, Akron, OH 44325-3601, USA.
Chemistry. 2022 Nov 7;28(62):e202202192. doi: 10.1002/chem.202202192. Epub 2022 Sep 2.
During the past two decades, single-atom-centered medium-sized germanium clusters [M@Ge ] (M=transition metals, n>12) have been extensively explored, both from theoretical perspectives and experimental gas-phase syntheses. However, the actual structural arrangements of the Ge and Ge endohedral cages are still ambiguous and have long remained an unresolved problem for experimental implementation. In this work, we successfully synthesize 13-/14-vertex Ge clusters [Nb@Ge ] (1) and [Nb@Ge ] (2), which are structurally characterized and exhibit unprecedented topologies, neither classical deltahedra nor 3-connected polyhedral structures. Theoretical analysis indicates that the major stabilization of the Ge backbones arises due to the substantial interaction of Ge 4p-AOs with the endohedral Nb 4d-AOs through three/four-center two-electron bonds with an enhanced electron density accumulated over the shortest Nb-Ge13 contact in 1. Low occupancies of the direct two-center two-electron (2c-2e) Nb-Ge and Ge-Ge σ bonds point to a considerable degree of electron delocalization over the Ge cages revealing their electron deficiency.
在过去二十年中，以单原子为中心的中等尺寸锗簇合物[M@Geₙ]（M = 过渡金属，n > 12），无论是从理论角度还是实验气相合成方面都得到了广泛研究。然而，锗和包合物笼的实际结构排列仍然不明确，长期以来一直是实验实施中未解决的问题。在这项工作中，我们成功合成了13/14顶点的锗簇合物[Nb@Ge₁₃]（1）和[Nb@Ge₁₄]（2），对其进行了结构表征，它们展现出前所未有的拓扑结构，既不是经典的 deltahedron 结构，也不是 3 - 连通多面体结构。理论分析表明，锗骨架的主要稳定性源于锗 4p 原子轨道与包合的铌 4d 原子轨道通过三中心/四中心双电子键的大量相互作用，在 1 中，电子密度在最短的铌 - 锗₁₃接触上积累增强。直接的双中心双电子（2c - 2e）铌 - 锗和锗 - 锗 σ 键的低占有率表明，在锗笼上存在相当程度的电子离域，揭示了它们的电子缺乏。
