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

Abstract

The parameters relevant to aromaticity of boron-rich inorganic benzene analogues (B4N2R6) have been computationally investigated by using HOMA, ELF, PDI, NICSzz, ACID and ASE.

A Crystalline B4N2 Dewar Benzene as a Building Block for Conjugated B,N-Chains

“…To begin our investigation, we performed ab initio calculations at the B3LYP/6-311G level of theory (Table ). The relative energies of three structuresdistorted boat A , benzene B , and Dewar benzene C of B 4 N 2 benzene scaffolds with different substituents indicate that 1-A is the most stable for entry 1, whereas 2-B is the most stable for entry 2, in line with our previous reports . Significantly, when a mesityl group (Mes), a dimethylamino group (NMe 2 ), and trimethyl phosphine (PMe 3 ) are employed as R 1 , R 2 , and R 3 , respectively, Dewar benzene 3-C appears to be the most stable structure among them (entry 3).…”

“…Recently, we reported the synthesis of 1,4-diaza-2,3,5,6-tetraborinine (B 4 N 2 ) derivatives of the formal 6π electron system (Table ). The isolated dianionic species 1-A has a distorted boat structure with a four-center two-electron bond among the skeletal boron atoms, whereas a neutral species with a planar structure 2-B exhibits a moderate aromatic nature. Given the reported substituent effect on the relative stability of valence isomers, we reasoned that B 4 N 2 Dewar-type benzene can be prepared by tuning the proper substituent.…”

The hidden aromaticity in borazine

“…The geometric criterion through the harmonic oscillator model of aromaticity (HOMA) indicates that the aromaticity of borazine is similar to that of benzene, while the delocalization criterion indicates a lower degree of aromaticity. 28 Surprisingly, Udagawa and Iwaki 8 indicate that borazine exhibits an antiaromatic character according to multiconfigurational calculations. However, this method has not been well tested as an aromaticity criterion.…”