Tetra‐tert‐butyl‐s‐indacene is a Bond‐Localized C2h Structure and a Challenge for Computational Chemistry

Whether tetra‐tert‐butyl‐s‐indacene is a symmetric D2h structure or a bond‐alternating C2h structure remains a standing puzzle. Close agreement between experimental and computed proton chemical shifts based on minima structures optimized at the M06‐2X, ωB97X‐D, and M11 levels confirm a bond‐localize...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2023-09, Vol.62 (36), p.e202307379-n/a
Main Authors: Karas, Lucas J., Jalife, Said, Viesser, Renan V., Soares, João V., Haley, Michael M., Wu, Judy I.
Format: Article
Language:English
Subjects:
Antiaromaticity
B3LYP
Computational chemistry
Density Functional Theory
Expanded π-Conjugated Systems
s-Indacene
Symmetry
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Summary:Whether tetra‐tert‐butyl‐s‐indacene is a symmetric D2h structure or a bond‐alternating C2h structure remains a standing puzzle. Close agreement between experimental and computed proton chemical shifts based on minima structures optimized at the M06‐2X, ωB97X‐D, and M11 levels confirm a bond‐localized C2h symmetry, which is consistent with the expected strong antiaromaticity of TtB‐s‐indacene. The structure of tetra‐tert‐butyl‐s‐indacene is a computational challenge. Highly correlated methods and popular DFT functionals predict a bond‐delocalized D2h symmetry, but excellent agreement between experimental and computed proton chemical shifts suggests a true C2h geometry.
ISSN:1433-7851
1521-3773
1521-3773
DOI:10.1002/anie.202307379