Lei Xin, Zhang Hanyu, Jia Yuhan, Luo Zhixun
State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
Phys Chem Chem Phys. 2021 Jul 28;23(29):15766-15773. doi: 10.1039/d1cp02128a.
We report a study of the reactions of pure metal clusters Nbn- with dioxygen in the gas phase. It is found that the presence of low-concentration dioxygen reactants results in oxygen-addition products, whereas sufficient high-concentration dioxygen enables oxygen-etching reactions giving rise to molecular niobium oxides. Interestingly, in the presence of a suitable gas flow rate of an intermediate dioxygen concentration, a highly selective product Nb11O15- shows up in the mass spectra. Utilizing density functional theory (DFT) calculations, we have discussed the reactivities of Nbn- (3 ≤ n ≤ 14) clusters with oxygen, and unveiled the reasonable stability of Nb11O15- pertaining to its unique geometric structure with a D5h Nb@Nb10 core fully protected by 15 bridge-oxygen atoms. The oxygen-passivated Nb@Nb10O15- cluster exhibits a large HOMO-LUMO gap (1.46 eV) and effective multicenter bonds with remarkable superatom orbitals for all the 26 valence electrons of the Nb@Nb10 core corresponding to well-staggered energy levels. We illustrate the superatomic features in the Nb@Nb10 metallic core for which the adaptive natural density partitioning (AdNDP) analysis unveils thirteen 11c-2e bonds. Among them, one of the 11c-2e bonds accounts for the superatomic S orbital, three bonds correspond to superatomic P orbitals, another five display vivid D orbital characteristics, and the remaining four 11c-2e bonds are assigned to F orbital features. In addition, the net atomic charge of the center Nb atom is as high as -0.804 |e| rendering core-shell electrostatic interactions and the shielding effect of the Nb10O15 shell.
我们报道了一项关于纯金属团簇Nbn-与气相中的双氧反应的研究。研究发现，低浓度双氧反应物的存在会导致氧加成产物的生成，而足够高浓度的双氧则能引发氧蚀刻反应，生成分子态的铌氧化物。有趣的是，在适当的中间双氧浓度气流速率存在的情况下，质谱中会出现一种高选择性产物Nb11O15-。利用密度泛函理论（DFT）计算，我们讨论了Nbn-（3≤n≤14）团簇与氧的反应活性，并揭示了Nb11O15-因其独特的几何结构而具有合理的稳定性，其D5h Nb@Nb10核被15个桥氧原子完全保护。氧钝化的Nb@Nb10O15-团簇表现出较大的HOMO-LUMO能隙（1.46 eV）以及有效的多中心键，对于Nb@Nb10核的所有26个价电子具有显著的超原子轨道，对应着排列良好交错的能级。我们阐述了Nb@Nb10金属核中的超原子特征，自适应自然密度划分（AdNDP）分析揭示了其中有13个11c-2e键。其中，一个11c-2e键对应超原子S轨道，三个键对应超原子P轨道，另外五个显示出鲜明的D轨道特征，其余四个11c-2e键归属于F轨道特征。此外，中心Nb原子的净原子电荷高达-0.804 |e|，呈现出核壳静电相互作用以及Nb10O15壳层的屏蔽效应。
