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In Situ Observation of Non‐Classical 2‐Norbornyl Cation in Confined Zeolites at Ambient Temperature
Author(s) -
Tang Xiaomin,
Chen Wei,
Yi Xianfeng,
Liu Zhiqiang,
Xiao Yao,
Chen Zhongfang,
Zheng Anmin
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202013384
Subject(s) - 2 norbornyl cation , carbocation , delocalized electron , carbonium ion , in situ , zeolite , ion , characterization (materials science) , chemistry , ab initio , resonance (particle physics) , chemical physics , computational chemistry , materials science , photochemistry , nanotechnology , catalysis , organic chemistry , physics , atomic physics
Carbonium ions are an important class of reaction intermediates, but their dynamic evolution is difficult to be monitored by in situ techniques under experimental conditions because of their extremely short lifetime. Probably the most famous case is 2‐norbornyl cation (2NB + ): its existing form (classical or non‐classical) had been debated for decades, until the concrete proof of non‐classical geometry was achieved by X‐ray crystallographic characterization at ultra‐low temperature (40 K) and super acidic environment. However, we lack the understanding about 2NB + at ambient conditions. Herein, by taking advantage of the confinement effect and delocalized acidic environment of zeolites, we successfully stabilized 2NB + and unequivocally confirmed its “non‐classical” structure inside the ZSM‐5 zeolite by ab initio molecular dynamics simulations and 13 C solid‐state nuclear magnetic resonance experiments. It is the first time to in situ observe the non‐classical 2NB + without the super acidic environment at ambient temperature, which provides a new strategy to expand the carbocation chemistry.