Craig-Type Möbius Aromaticity and Antiaromaticity in Dimetallaannulenes: A Metal-Induced Yin-and-Yang Pair
Aromaticity, one of the most fundamental concepts in chemistry, can be classified as Hückel- and Möbius-type according to the electron count and topology. In comparison with numerous Hückel aromatics containing 4n+2 π-electrons, Möbius aromatics with 4n π-electrons, especially the Craig-type species are particularly limited. Herein we demonstrate that the recently synthesized dimetallaannulenes could be Möbius aromatic or antiaromatic although the organic prototype annulene is nonaromatic due to the nonplanarity caused by the steric repulsion of two CH groups, suggesting the first example of yin-and-yang pair with Craig-type Möbius (anti)aromaticity. Further study suggests that the lithium atoms in dimetallaannulenes are not spectator cations but play an important role in the aromaticity switch of these species due to their bonding interaction with the diene moieties. Our findings highlight the magic power of metals in the achievement of Craig-type Möbius aromatics, thus opening an avenue to such novel aromatics.