Nitrogen versus carbon in planar pentacoordinate environments supported by Be 5 H n rings

• Published in: RSC advances 2021-04, Vol.11 (26), p.15841-15846
• Main Authors: Bian, Jian-Hong, Jin, Bo, Zhao, Xue-Feng, Sun, Rui, Yuan, Caixia, Zhou, Cheng-Yong, Wu, Yan-Bo
• Format: Article
• Language: English
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/D1RA02178H

NBe H ( = 0-5) (0A-5A) species with a novel planar pentacoordinate nitrogen (ppN) were designed by the isoelectronic substitution of the C atom in planar pentacoordinate carbon (ppC) species CBe H ( = 0-5) with an N atom. The highly flexible H atoms found in ppC species CBe H and CBe H were fixed upon the nitrogen substitution, as mirrored by the non-flexible H atoms in their ppN analogues NBe H (2A) and NBe H (3A). Moreover, the N atom was found to fit the H-surrounded Be rings better than the C atom because the ppC species CBe H and CBe H adopted non-planar structures due to size-mismatch between the C atom and the H-surrounded Be ring, but their ppN analogues NBe H (4A) and NBe H (5A) adopted perfect planar structures. The electronic structure analyses revealed that the N atoms in 0A-5A were involved in four doubly occupied orbitals, including three six-center two-electron (6c-2e) σ bonds and one 6c-2e π bond. Therefore, these ppN species not only obey the octet rule, but also possess the interesting σ and π double aromaticity, which contributes to the stabilization. Consequently, 2A, 4A, and 5A are charged kinetically viable global energy minima, and are suitable for the gas phase generation and spectroscopic characterization.