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Reduction of π‐Expanded Cyclooctatetraene with Lithium: Stabilization of the Tetra‐Anion through Internal Li + Coordination
Author(s) -
Zhou Zheng,
Zhu Yikun,
Wei Zheng,
Bergner John,
Neiß Christian,
Doloczki Susanne,
Görling Andreas,
Kivala Milan,
Petrukhina Marina A.
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202013353
Subject(s) - cyclooctatetraene , chemistry , lithium (medication) , tetra , carbanion , moiety , nmr spectra database , ion , density functional theory , crystal structure , crystallography , inorganic chemistry , medicinal chemistry , stereochemistry , computational chemistry , molecule , spectral line , organic chemistry , medicine , physics , astronomy , endocrinology
The chemical reduction of a π‐expanded polycyclic framework comprising a cyclooctatetraene moiety, octaphenyltetrabenzocyclooctatetraene, with lithium metal readily affords the corresponding tetra‐anion instead of the expected aromatic dianion. As revealed by X‐ray crystallography, the highly contorted tetra‐anion is stabilized by coordination of two internally bound Li + , while two external cations remain solvent separated. The variable‐temperature 7 Li NMR spectra in THF confirm the presence of three types of Li + ions and clearly differentiate internal binding, consistent with the crystal structure. Density‐functional theory calculations suggest that the formation of the highly charged tetra‐reduced carbanion is stabilized through Li + coordination under the applied experimental conditions.