Aromatic nature of neutral and dianionic 1,4-diaza-2,3,5,6-tetraborinine derivatives

Abstract

The aromatically relevant parameters of boron-rich inorganic benzenes—neutral and dianionic 1,4-diaza-2,3,5,6-tetraborinine derivatives (B₄N₂R₆)—have been computationally estimated and evaluated from geometric, electronic, magnetic, and energetic points of view. The majority of the criteria (ASE, NICS_zz, ELF, and PDI) indicate that the aromaticity of the neutral B₄N₂ benzene analogue stabilized by Lewis bases lies in between those of benzene and borazine. On the other hand, the aromaticity of the dianionic B₄N₂ benzene analogue 4′ is controversial. The pronounced aromatic nature of 4′ is supported by ELF_π, PDI, and NICS_πzz, but ASE, the FiPC-NICS plot, and ACID oppose this. These data confirm that even with the same B₄N₂-skeletal framework of a 6π-system, the aromatic feature varies depending on the overall charge of the B₄N₂ systems.