Cao Guo-Jin, Schwarz W H Eugen, Li Jun
†Key Laboratory of Chemical Biology and Molecular Engineering of the Education Ministry, Institute of Molecular Science, Shanxi University, Taiyuan 030006, China.
§Department of Chemistry and Key Laboratory of Organic Optoelectronics and Molecular Engineering, Ministry of Education, Tsinghua University, Beijing 100084, China.
Inorg Chem. 2015 Apr 6;54(7):3695-701. doi: 10.1021/acs.inorgchem.5b00356. Epub 2015 Mar 23.
M@Au12 cage molecules (M = transition element from group 6) are interesting clusters with high-symmetric structure and significant stability. As the heavier homologue of W is (106)Sg, it is interesting to pinpoint whether the Sg@Au12 cluster is also stable. Geometric and electronic structures and bonding of various Sg@Au12 isomers were investigated with density functional theory (PW91, PBE, B3LYP) and wave function theory (MP2, CCSD(T)) approaches. The lowest-energy isomer of Sg@Au12 has icosahedral symmetry with significant Sg(6d)-Au(6s) covalent-metallic interaction and is comparable to the lighter homologues (M = Mo, W), with similar binding energy, although Sg follows (as a rare case) the textbook rule "ns below (n - 1)d". The 12 6s valence electrons from Au12 and the six 7s6d ones from Sg can be viewed as an 18e system below and above the interacting Au 5d band, forming nine delocalized multicenter bond pairs with a high stability of ∼0.8 eV of bond energy per each of the 12 Sg-Au contacts. Different prescriptions (orbital, multipole-deformation, charge-partition, and X-ray-spectroscopy based ones) assign ambiguous atomic charges to the centric and peripheral atoms; atomic core-level energy shifts correspond to some negative charge shift to the gold periphery, more so for Cr@Au12 than for Sg@Au12 or Au@Au12.
M@Au12笼状分子（M = 第6族过渡元素）是具有高对称结构和显著稳定性的有趣簇合物。由于W的较重同系物是（106）Sg，确定Sg@Au12簇是否也稳定很有意思。利用密度泛函理论（PW91、PBE、B3LYP）和波函数理论（MP2、CCSD(T)）方法研究了各种Sg@Au12异构体的几何结构、电子结构和键合。Sg@Au12的最低能量异构体具有二十面体对称性，具有显著的Sg(6d)-Au(6s)共价-金属相互作用，并且与较轻的同系物（M = Mo、W）相当，具有相似的结合能，尽管Sg（作为一个罕见的例子）遵循教科书规则“ns低于(n - 1)d”。来自Au12的12个6s价电子和来自Sg的6个7s6d电子可以看作是相互作用的Au 5d能带上下的一个18电子体系，形成9个离域多中心键对，每个12个Sg-Au接触的键能稳定性约为0.8 eV。不同的规定（基于轨道、多极变形、电荷划分和X射线光谱的规定）给中心和外围原子赋予了模糊的原子电荷；原子芯能级能量位移对应于一些负电荷向金外围的转移，对于Cr@Au12比对于Sg@Au12或Au@Au12更是如此。
