Reduction vs. Addition: The Reaction of an Aluminyl Anion with 1,3,5,7‐Cyclooctatetraene

The potassium aluminyl complex K[Al(NONAr)] (NON=NONAr=[O(SiMe2NAr)2]2−, Ar=2,6‐iPr2C6H3) reacts with 1,3,5,7‐cyclooctatetraene (COT) to give K[Al(NONAr)(COT)]. The COT‐ligand is present in the asymmetric unit as a planar μ2‐η2:η8‐bridge between Al and K, with additional K⋅⋅⋅π‐aryl interactions to n...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2019-01, Vol.58 (5), p.1489-1493
Main Authors: Schwamm, Ryan J., Anker, Mathew D., Lein, Matthias, Coles, Martyn P.
Format: Article
Language:English
Subjects:
aluminyl anion
Anions
Aromatic compounds
COT ligand
cycloaddition
isomeric anions
Potassium
Reduction
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Summary:The potassium aluminyl complex K[Al(NONAr)] (NON=NONAr=[O(SiMe2NAr)2]2−, Ar=2,6‐iPr2C6H3) reacts with 1,3,5,7‐cyclooctatetraene (COT) to give K[Al(NONAr)(COT)]. The COT‐ligand is present in the asymmetric unit as a planar μ2‐η2:η8‐bridge between Al and K, with additional K⋅⋅⋅π‐aryl interactions to neighboring molecules that generate a helical chain. DFT calculations indicate significant aromatic character, consistent with reduction to [COT]2−. Addition of 18‐crown‐6 causes a rearrangement of the C8‐carbocycle to form the isomeric 9‐aluminabicyclo[4.2.1]nona‐2,4,7‐triene anion. Uneasy lies the head that wears a crown: The initial product from the reaction of a two‐coordinate aluminyl anion with 1,3,5,7‐cyclooctatetraene (COT) contains the reduced COT‐ligand with pronounced aromatic character. Addition of 18‐crown‐6 to K[Al(NONAr)(COT)] promotes isomerization of the carbocycle to afford the 9‐aluminabicyclo[4.2.1]nona‐2,4,7‐triene anion.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201811675