Quest for Double Möbius Aromaticity

Abstract

Neutral four-membered rings with 4n electrons are generally Hückel antiaromatic. On the other hand, 4n electron system can also be Möbius aromatic, although identification has escaped so far. A recent study of double Möbius aromaticity has been put forwarded in the D_2h symmetric singlet ground state of four member Pa₂B₂ ring. Although interesting, but the synthesis possesses a significant challenge as Pa is rare, highly radioactive and toxic. Herein, a synthetically viable four membered Rh₂B₂ cluster is proposed which contains double Möbius aromaticity. Interestingly, the three membered RhB₂ ^- cluster also possess Möbius aromaticity and is the smallest ring to show such phenomenon.