Structure determination of a bis[4‐(di‐n‐butylamino)phenyl](pyridin‐3‐yl)borane tetramer highlighting a unique geometric conformation of the core 16‐membered ring

• Published in: Acta crystallographica. Section C, Crystal structure communications Crystal structure communications, 2023-05, Vol.79 (5), p.170-176
• Main Authors: Lovstedt, Alex, Dempsey, Stephen H., Kass, Steven R.
• Format: Article
• Language: English
• Subjects: 16‐membered ring; borane; Boranes; Boron; crystal structure; Crystallization; Density functional theory; DFT calculations; organocatalysis; ring conformation; zwitterion
• ISSN: 2053-2296; 0108-2701; 2053-2296; 1600-5759
• DOI: 10.1107/S2053229623002619

The tetramer of bis(4‐di‐n‐butylaminophenyl)(pyridin‐3‐yl)borane [systematic name: 2λ4,4λ4,6λ4,8λ4‐tetrabora‐1,3,5,7(1,3)‐tetrapyridinacyclooctaphane‐11,31,51,71‐tetrakis(ylium)], C132H192B4N12, was synthesized unexpectedly and crystallized. Its structure contains an unusual 16‐membered ring core made up of four (pyridin‐3‐yl)borane groups. The ring adopts a conformation with pseudo‐S4 symmetry that is very different from the two other reported examples of this ring system. Density functional theory (DFT) computations indicate that the stability of the three reported ring conformations is dependent on the substituents on the B atoms, and that the pseudo‐S4 geometry observed in the bis(4‐dibutylaminophenyl)(pyridin‐3‐yl)borane tetramer becomes significantly more stable when phenyl or 2,6‐dimethylphenyl groups are attached to the boron centers. The tetramer of bis[4‐(di‐n‐butylamino)phenyl](pyridin‐3‐yl)borane was synthesized unexpectedly and crystallized. Its structure contains an unusual 16‐membered ring core made up of four (pyridin‐3‐yl)borane groups. The ring adopts a conformation with pseudo‐S4 symmetry that is very different from the two other reported examples of this ring system.