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Abstract The addition of non‐benzenoid quinones, acenapthenequinone or aceanthrenequinone, to the 9‐carbene‐9‐borafluorene monoanion (1) affords the first examples of dianionic 10‐membered bora‐crown ethers (2–5), which are characterized by multi‐nuclear NMR spectroscopy (1H,13C,11B), X‐ray crystallography, elemental analysis, and UV/Vis spectroscopy. These tetraoxadiborecines have distinct absorption profiles based on the positioning of the alkali metal cations. When compound4, which has a vacant C4B2O4cavity, is reacted with sodium tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate, a color change from purple to orange serves as a visual indicator of metal binding to the central ring, whereby the Na+ion coordinates to four oxygen atoms. A detailed theoretical analysis of the calculated reaction energetics is provided to gain insight into the reaction mechanism for the formation of2–5. These data, and the electronic structures of proposed intermediates, indicate that the reaction proceeds via a boron enolate intermediate.
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This content will become publicly available on May 30, 2026
Supramolecular assembly of hypervalent iodine macrocycles and alkali metals
This study explores the solution- and solid-state assembly of phenylalanine-based hypervalent iodine macrocycles (HIMs) with lithium and sodium cations. The metal cation binding of HIMs was evaluated by addition of lithium tetrakis(pentafluorophenyl)borate ethyl etherate LiBArF20and sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate NaBArF24. The electron-rich, outwardly projected carbonyl oxygens of the HIM co-crystalize with the cations into bent supramolecular architectures. Both crystal structures show a pattern of assembly between HIM and metal cation in 2:1 ratio. While association with sodium leads to a polymer-like network, the lithium crystal structure was limited to dimeric assemblies of HIM. In the lithium-coordinating complex, the oxygen–lithium–oxygen bond angle is approximately 98.83°, displaying a closer arrangement of two HIMs. In contrast, the sodium complex exhibits a more open orientation of two HIMs with an oxygen–sodium–oxygen bond angle close to 167.98°. Lastly, a comparative study of association constants and binding energies for phenylalanine-based HIM with LiBArF20and NaBArF24are presented.
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- Award ID(s):
- 2003654
- PAR ID:
- 10659205
- Publisher / Repository:
- Beilstein-Institut zur Förderung der Chemischen Wissenschaften
- Date Published:
- Journal Name:
- Beilstein Journal of Organic Chemistry
- Volume:
- 21
- ISSN:
- 1860-5397
- Page Range / eLocation ID:
- 1095 to 1103
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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