物理化学学报 >> 2018, Vol. 34 >> Issue (7): 830-836.doi: 10.3866/PKU.WHXB201712151

所属专题: 原子水平上精确控制纳米簇和纳米粒子

论文 上一篇    

八电子Pd4四面体团簇的电子结构稳定性分析

沈艳芳1,程龙玖1,2,*()   

  1. 1 安徽大学化学化工学院,合肥 230601
    2 安徽省有机/无机杂化功能材料重点化学实验室,合肥 230601
  • 收稿日期:2017-10-31 发布日期:2018-03-26
  • 通讯作者: 程龙玖 E-mail:clj@ustc.edu
  • 基金资助:
    国家自然科学基金(21573001);安徽省杰出青年科学家基金资助项目

Electronic Stability of Eight-electron Tetrahedral Pd4 Clusters

Yanfang SHEN1,Longjiu CHENG1,2,*()   

  1. 1 School of Chemistry and Chemical Engineering, Anhui University, Hefei 230601, P. R. China
    2 Anhui Province Key Laboratory of Chemistry for Inorganic/Organic Hybrid Functionalized Materials, Hefei 230601, P. R. China
  • Received:2017-10-31 Published:2018-03-26
  • Contact: Longjiu CHENG E-mail:clj@ustc.edu
  • Supported by:
    by the National Natural Science Foundation of China(21573001);the Foundation of Distinguished Young Scientists of Anhui Province, China

摘要:

基于理论计算,我们报道了Td对称性的[Pd4(μ3-SbH3)4(SbH3)4]团簇及一系列类似物的结构与成键。成键分析表明:每个Pd原子都是sp3杂化,其10个价电子与四个配体提供的8个价电子,满足18电子规则。并且,每个Pd原子与四个桥连的SbH3配体可以形成四个离域的四中心两电子超级σ键或八中心两电子键。一方面,根据超原子网络模型,这个钯团簇可以描述成四个2电子的超原子网络。另一方面,凝胶模型表明,它可以合理化的作为电子组态是1S21P6的8电子超原子。与此同时,d10d10闭壳层相互作用在稳定Pd4四面体结构中起到了关键性的作用。密度泛函理论计算表明:Td对称性[Pd4(μ3-SbH3)4(SbH3)4]团簇表现出高度稳定性,具有充满的电子壳层,大的HOMO-LUMO带隙(2.84 eV)以及负的核独立化学位移(NICS)值。此外,基于[Pd4(μ3-SbH3)4(SbH3)4]结构与成键模式,我们设计了一系列稳定的类似物,其有可能被实验合成出来。

关键词: 金属团簇, 超价键, 超原子, 化学键分析, 闭壳层相互作用, 芳香性

Abstract:

Motivated by the unusual structure of the [Pd4(μ3-SbMe3)4(SbMe3)4] cluster, which is composed of a tetrahedral (Td) Pd(0) core with four terminal SbMe3 ligands and four triply bridging SbMe3 ligands capping the four triangular Pd3 faces (J. Am. Chem. Soc. 2016, 138, 6964), we performed a computational study of the structure and bonding characteristics of the Td [Pd4(μ3-SbH3)4(SbH3)4] cluster and a series of its analogues. The Td structure of the [Pd4(μ3-SbH3)4(SbH3)4] cluster could be explained by the cluster electron-counting rules based on the 18-electron rule for transition-metal centers; each sp3 hybridized Pd atom contributed ten valence electrons, and eight valence electrons were provided by one terminal SbH3 and three bridging μ3-SbH3 ligands. The [Pd4(μ3-SbH3)4(SbH3)4] cluster had a count of 104 valence electrons in total; chemical bonding analysis indicated that the cluster featured twenty electron lone pairs generated by d orbital of the four Pd atoms, twenty-four Sb―H σ bonds, four terminal Pd―Sb σ bonds, and four delocalized bonds. There were two bonding patterns of the eight delocalized electrons between the four capping Sb atoms and the Pd4 core. The first pattern was based on the superatom-network (SAN) model, whereby the palladium cluster could be described as a network of four 2e superatoms. The second pattern was based on the spherical jellium model, whereby the cluster could be rationalized as an 8e [Pd4(μ3-SbH3)4] superatom with 1S21P6 electronic configuration. The density functional theory (DFT) calculations showed that the Td [Pd4(μ3-SbH3)4(SbH3)4] cluster had a large HOMO-LUMO (HOMO: highest occupied molecular orbital; LUMO: lowest unoccupied molecular orbital) energy gap (2.84 eV) and a negative nucleus-independent chemical shift (NICS) value (-12) at the center of the [Pd4(μ3-SbH3)4(SbH3)4] cluster, indicating its high chemical stability and aromaticity. Furthermore, the NICS values in the range of 0–0.30 nm of the [Pd4(μ3-SbH3)4] motifs were much more negative than those of [Pd4(SbH3)4] in the same range, revealing that the overall stability of [Pd4(μ3-SbH3)4(SbH3)4] was likely derived from the local stability of Pd4(μ3-SbH3)4. Meanwhile, the d10d10 interaction played a critical role in stabilizing the Pd4 tetrahedron structure, which is similar to the aurophilicity in Au-Au clusters. It was also found that there is a large difference in the stability of transition metal and non-transition metal clusters with a tetrahedron structure. The structures and bonding patterns of the designed analogues were similar to those of [Pd4(μ3-SbH3)4(SbH3)4]. To summarize, this study was relevant for deciphering the nature of the bonds in a tetrahedral complex with four cores and eight ligands, and predicting a series of analogues. It is expected that this work will provide more options for the synthesis of tetrahedral 4-core transition metal compounds.

Key words: Metal cluster, Super valence bond, Superatom, Chemical bonding analysis, Closed-shell interaction, Aromaticity

MSC2000: 

  • O641