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

The aromatically relevant parameters of boron-rich inorganic benzenes—neutral and dianionic 1,4-diaza-2,3,5,6-tetraborinine derivatives (B(4)N(2)R(6))—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 B(4)N(2) benzene analogue stabilized by Lewis bases lies in between those of benzene and borazine. On the other hand, the aromaticity of the dianionic B(4)N(2) 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 B(4)N(2)-skeletal framework of a 6π-system, the aromatic feature varies depending on the overall charge of the B(4)N(2) systems.