Huang Benben, Zhang Hanyu, Gan Wen, Yang Mengzhou, Luo Zhixun, Yao Jiannian
Beijing National Laboratory of Molecular Sciences (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
School of Chemical Science, University of Chinese Academy of Sciences, Beijing 100049, China.
Natl Sci Rev. 2022 Sep 22;10(3):nwac197. doi: 10.1093/nsr/nwac197. eCollection 2023 Mar.
Why one chemical is more stable than another is not always easy to understand. A unified answer for metal clusters has led to the establishment of the superatom concept, which rationalizes the delocalization of electrons; however, cluster stability based on superatom theory has not been confirmed unambiguously for any metal other than the s- and p-blocks of the periodic table of elements. Here, we have prepared pure niobium clusters and observed their reactions with CO under sufficient gas collision conditions. We find prominent inertness of Nb , which survives CO attack. Comprehensive theoretical calculation results reveal that the inertness of Nb is associated with its cage structure and well-organized superatomic orbitals, giving rise to energetic superiority among the studied clusters. It is revealed that not only the 5s but also the 4d electrons of Nb delocalize in the cluster and significantly contribute to the superatomic state, resulting in reasonable cage aromaticity. This hollow-cage cluster, which we have called a 'niobespherene', provides a clue with regard to designing new materials of all-metal aromaticity and Nb-involved catalysts free of CO poisoning.
为何一种化学物质比另一种更稳定，这并不总是容易理解。对金属团簇的统一解释催生了超原子概念，该概念使电子离域合理化；然而，除了元素周期表的s区和p区元素外，基于超原子理论的团簇稳定性尚未在任何其他金属中得到明确证实。在此，我们制备了纯铌团簇，并观察了它们在充分的气体碰撞条件下与CO的反应。我们发现Nb具有显著的惰性，能经受住CO的攻击。综合理论计算结果表明，Nb的惰性与其笼状结构和有序的超原子轨道有关，这使其在所研究的团簇中具有能量优势。结果表明，Nb的5s电子和4d电子不仅在团簇中离域，而且对超原子态有显著贡献，从而产生合理的笼状芳香性。这种我们称为“铌球烯”的空心笼状团簇，为设计具有全金属芳香性且不含CO中毒的含Nb催化剂的新材料提供了线索。
