For instance, although Heilbronner pointed out in 1964 that rings with 20 atoms or more might adopt Möbius geometries ‘without any apparent angle or steric repulsion strain’ in his prediction 4, Mauksch et al. Indeed, the reported Möbius aromatic compounds are very limited and almost all have twisted topologies 14, 15, 16, 17, 18. Although Hückel aromatic compounds with 4 n+2 mobile electrons are common, examples of Möbius 4 n electrons aromaticity have proven to be much more difficult to realize and to establish 4, 5, 6, 7, 8, 9, 10, 11, 12, 13. Our results widen the scope of Möbius aromaticity dramatically and open prospects for the generalization of planar Möbius aromatic chemistry.Īromaticity, one of the most important concepts in chemistry, denotes the ‘extra’ stabilization of molecules because of electron delocalization in closed circuits 1, 2, 3. All these osmapentalenes are formed by both electrophilic and nucleophilic reactions of the in-plane π component of the same carbyne carbon, illustrating ambiphilic carbyne reactivity, which is seldom observed in transition metal chemistry. The Möbius aromaticity of these osmapentalenes, documented by X-ray structural, magnetic and theoretical analyses, demonstrates the basis of the aromaticity of the parent osmapentalynes. Here we report the realization of osmapentalenes, the first planar Möbius aromatic complexes with 16 and 18 valence electron transition metals. Although the Möbius concept extends the principle of aromaticity to 4 n mobile electron species, the rare known examples have complex, twisted topologies whose extension is unlikely.
Aromaticity, a highly stabilizing feature of molecules with delocalized electrons in closed circuits, is generally restricted to ‘Hückel’ systems with 4 n+2 mobile electrons.
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