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

The potassium aluminyl complex K[Al(NON Ar )] (NON=NON Ar =[O(SiMe 2 NAr) 2 ] 2− , Ar=2,6‐ i Pr 2 C 6 H 3 ) reacts with 1,3,5,7‐cyclooctatetraene (COT) to give K[Al(NON Ar )(COT)]. The COT‐ligand is present in the asymmetric unit as a planar μ 2 ‐η 2 :η 8 ‐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 C 8 ‐carbocycle to form the isomeric 9‐aluminabicyclo[4.2.1]nona‐2,4,7‐triene anion.