Jian Tian, Cheung Ling Fung, Czekner Joseph, Chen Teng-Teng, Lopez Gary V, Li Wei-Li, Wang Lai-Sheng
Department of Chemistry , Brown University , Providence , Rhode Island 02912 , USA . Email:
Chem Sci. 2017 Nov 1;8(11):7528-7536. doi: 10.1039/c7sc02881d. Epub 2017 Sep 15.
We report a photoelectron spectroscopy and high-resolution photoelectron imaging study of a bimetallic NbAu cluster. Theoretical calculations, in conjunction with the experimental data, reveal that NbAu possess high-symmetry structures featuring a Nb-Nb axis coordinated equatorially by an Au ring. Chemical bonding analyses show that there are two π bonds and one σ bond in the Nb moiety in Nb©Au, as well as five totally delocalized σ bonds. The Nb[triple bond, length as m-dash]Nb triple bond is strengthened significantly by the delocalized σ bonds, resulting in an extremely short Nb-Nb bond length comparable to the quintuple bond in gaseous Nb. The totally delocalized σ bonding in Nb©Au is reminiscent of σ aromaticity, representing a new bonding mode in metal-ligand systems. The unusually short Nb-Nb bond length in Nb©Au shows that the Au ring can serve as a bridging ligand to facilitate multiple bonding in transition metal dimers delocalized σ bonding.
我们报道了对双金属NbAu团簇的光电子能谱和高分辨率光电子成像研究。理论计算与实验数据相结合表明，NbAu具有高对称结构，其特征是Nb-Nb轴由一个Au环在赤道方向配位。化学键分析表明，在Nb©Au的Nb部分存在两个π键和一个σ键，以及五个完全离域的σ键。Nb[三键，长度为m破折号]Nb三键通过离域的σ键得到显著加强，导致Nb-Nb键长极短，可与气态Nb中的五重键相媲美。Nb©Au中完全离域的σ键让人联想到σ芳香性，代表了金属-配体体系中的一种新的键合模式。Nb©Au中异常短的Nb-Nb键长表明，Au环可以作为桥连配体，促进过渡金属二聚体中的多重键合和离域σ键合。
