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

Ota, Kei; Kinjo, Rei

doi:10.1039/d0ra09040a

Cited by 2 publications

(3 citation statements)

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“…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).…”

Section: Resultssupporting

confidence: 88%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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

Ota

Kinjo

2021

J. Am. Chem. Soc.

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Dewar benzene, one of the isolable valence isomers of C6H6, has been extensively studied since its first synthesis in 1962. By contrast, the chemistry of inorganic congeners of Dewar benzene, which can be formally gained by replacing the skeletal carbon atoms with heteroatoms, has been less developed despite their peculiar structural and electronic features. Among them, the extant B,N-Dewar benzenes are limited to the B3N3 system. Herein, we report the development of the first example of an isolable B4N2 Dewar benzene, 3. As predicted by DFT calculations, a judicious selection of the substituents allows synthesizing 3. Single-crystal X-ray analysis, NMR, and computational studies confirmed that 3 possesses a high-lying B(sp3)–B(sp3) σ-bond at the bridgehead position. Reactions with ethylene and phenylacetylene proceeded smoothly under mild conditions, affording the fused B4C4N2 ring systems (4 and 5). Structural characterization as well as DFT calculations revealed that compounds 4 and 5 involve a rigid and conjugated (BN)4 tetraene scaffold. Formation of 4 and 5 demonstrates that 3 may serve as a building block for the construction of conjugated B,N-chains.

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Section: Resultssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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

Ota

Kinjo

2021

J. Am. Chem. Soc.

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“…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.…”

Section: Introductionmentioning

confidence: 99%