PdII Complexes of [44]- and [46]Decaphyrins: The Largest Hückel Aromatic and Antiaromatic, and Möbius Aromatic Macrocycles

Reductive metalation of [44]decaphyrin with [Pd2(dba)3] provided a Hückel aromatic [46]decaphyrin PdII complex, which was readily oxidized upon treatment with DDQ to produce a Hückel antiaromatic [44]decaphyrin PdII complex. In CH2Cl2 solution the latter complex underwent slow tautomerization to a Möbius aromatic [44]decaphyrin PdII complex which exists as a mixture of conformers in dynamic equilibrium. To the best of our knowledge, these three PdII complexes represent the largest Hückel aromatic, Hückel antiaromatic, and Möbius aromatic complexes to date. A new twist: Reductive metalation of [44]decaphyrin with [Pd2(dba)3] (dba=dibenzylideneacetone) provided a Hückel aromatic [46]decaphyrin PdII complex, which was quickly oxidized with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone to produce a Hückel antiaromatic [44]decaphyrin PdII complex. On standing in CH2Cl2 solution this complex slowly tautomerizes to a Möbius aromatic [44]decaphyrin PdII complex, giving an equilibrium mixture.