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1,3,2,5-Diazadiborinine featuring nucleophilic and electrophilic boron centres.

Wu D, Kong L, Li Y, Ganguly R, Kinjo R - Nat Commun (2015)

Bottom Line: In marked contrast to the reactivity of benzene, borazine, and even azaborinines previously reported, 1,3,2,5-diazadiborinine readily forms the adducts with methyl trifluoromethanesulfonate and phenylacetylene without any catalysts.Moreover, 1,3,2,5-diazadiborine activates carbon dioxide giving rise to a bicycle[2,2,2] product, and the binding process was found to be reversible.These results, thus, demonstrate that 1,3,2,5-diazadiborinine features both nucleophilic and electrophilic boron centres, with a formal B(+I)/B(+III) mixed valence system, in the aromatic six-membered B2C2N2 ring.

View Article: PubMed Central - PubMed

Affiliation: Division of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, 637371 Singapore, Singapore.

ABSTRACT
The seminal discovery in 1865 by Kekulé that benzene nucleus exists with cyclic skeleton is considered to be the beginning of aromatic chemistry. Since then, a myriad of cyclic molecules displaying aromatic property have been synthesized. Meanwhile, borazine (B3N3H6), despite the isostructural and isoelectronic relationships with benzene, exhibits little aromaticity. Herein, we report the synthesis of a 1,3,2,5-diazadiborinine (B2C2N2R6) derivative, a hybrid inorganic/organic benzene, and we present experimental and computational evidence for its aromaticity. In marked contrast to the reactivity of benzene, borazine, and even azaborinines previously reported, 1,3,2,5-diazadiborinine readily forms the adducts with methyl trifluoromethanesulfonate and phenylacetylene without any catalysts. Moreover, 1,3,2,5-diazadiborine activates carbon dioxide giving rise to a bicycle[2,2,2] product, and the binding process was found to be reversible. These results, thus, demonstrate that 1,3,2,5-diazadiborinine features both nucleophilic and electrophilic boron centres, with a formal B(+I)/B(+III) mixed valence system, in the aromatic six-membered B2C2N2 ring.

No MeSH data available.


Reactivity of 4.(a) Reactions of 4 with MeOTf, PhC≡CH and CO2 (13CO2). (b) Solid state structures of 5 (left), 6 (middle) and 7 (right). Thermal ellipsoids are set at the 30% probability level. Hydrogen atoms except for H1 in 6 and solvent molecules are omitted for clarity.
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f4: Reactivity of 4.(a) Reactions of 4 with MeOTf, PhC≡CH and CO2 (13CO2). (b) Solid state structures of 5 (left), 6 (middle) and 7 (right). Thermal ellipsoids are set at the 30% probability level. Hydrogen atoms except for H1 in 6 and solvent molecules are omitted for clarity.

Mentions: To investigate the reactivity of 4, we performed its reaction with methyl trifluoromethanesulfonate (MeOTf). A stoichiometric amount of MeOTf was added to an acetonitrile solution of 4 at ambient temperature. After removing the solvent under vacuum, 5 was obtained in 75% yield (Fig. 4a). An X-ray diffraction study confirmed that methyl group is attached to the boron atom between two carbons in the B2C2N2 ring, whereas an oxygen atom of the triflate is bounded to the boron atom between two nitrogen atoms (Fig. 4b, left). This result, thus, demonstrates that 4 features both nucleophilic and electrophilic boron centres, thereby supporting the electronic property of the resonance structure 4a (Fig. 1). The formal oxidation states of the B1 and the B2 atoms in 4a are +I and +III, respectively. Thus, 4 presents a donor–acceptor mixed valence system.


1,3,2,5-Diazadiborinine featuring nucleophilic and electrophilic boron centres.

Wu D, Kong L, Li Y, Ganguly R, Kinjo R - Nat Commun (2015)

Reactivity of 4.(a) Reactions of 4 with MeOTf, PhC≡CH and CO2 (13CO2). (b) Solid state structures of 5 (left), 6 (middle) and 7 (right). Thermal ellipsoids are set at the 30% probability level. Hydrogen atoms except for H1 in 6 and solvent molecules are omitted for clarity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4490389&req=5

f4: Reactivity of 4.(a) Reactions of 4 with MeOTf, PhC≡CH and CO2 (13CO2). (b) Solid state structures of 5 (left), 6 (middle) and 7 (right). Thermal ellipsoids are set at the 30% probability level. Hydrogen atoms except for H1 in 6 and solvent molecules are omitted for clarity.
Mentions: To investigate the reactivity of 4, we performed its reaction with methyl trifluoromethanesulfonate (MeOTf). A stoichiometric amount of MeOTf was added to an acetonitrile solution of 4 at ambient temperature. After removing the solvent under vacuum, 5 was obtained in 75% yield (Fig. 4a). An X-ray diffraction study confirmed that methyl group is attached to the boron atom between two carbons in the B2C2N2 ring, whereas an oxygen atom of the triflate is bounded to the boron atom between two nitrogen atoms (Fig. 4b, left). This result, thus, demonstrates that 4 features both nucleophilic and electrophilic boron centres, thereby supporting the electronic property of the resonance structure 4a (Fig. 1). The formal oxidation states of the B1 and the B2 atoms in 4a are +I and +III, respectively. Thus, 4 presents a donor–acceptor mixed valence system.

Bottom Line: In marked contrast to the reactivity of benzene, borazine, and even azaborinines previously reported, 1,3,2,5-diazadiborinine readily forms the adducts with methyl trifluoromethanesulfonate and phenylacetylene without any catalysts.Moreover, 1,3,2,5-diazadiborine activates carbon dioxide giving rise to a bicycle[2,2,2] product, and the binding process was found to be reversible.These results, thus, demonstrate that 1,3,2,5-diazadiborinine features both nucleophilic and electrophilic boron centres, with a formal B(+I)/B(+III) mixed valence system, in the aromatic six-membered B2C2N2 ring.

View Article: PubMed Central - PubMed

Affiliation: Division of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, 637371 Singapore, Singapore.

ABSTRACT
The seminal discovery in 1865 by Kekulé that benzene nucleus exists with cyclic skeleton is considered to be the beginning of aromatic chemistry. Since then, a myriad of cyclic molecules displaying aromatic property have been synthesized. Meanwhile, borazine (B3N3H6), despite the isostructural and isoelectronic relationships with benzene, exhibits little aromaticity. Herein, we report the synthesis of a 1,3,2,5-diazadiborinine (B2C2N2R6) derivative, a hybrid inorganic/organic benzene, and we present experimental and computational evidence for its aromaticity. In marked contrast to the reactivity of benzene, borazine, and even azaborinines previously reported, 1,3,2,5-diazadiborinine readily forms the adducts with methyl trifluoromethanesulfonate and phenylacetylene without any catalysts. Moreover, 1,3,2,5-diazadiborine activates carbon dioxide giving rise to a bicycle[2,2,2] product, and the binding process was found to be reversible. These results, thus, demonstrate that 1,3,2,5-diazadiborinine features both nucleophilic and electrophilic boron centres, with a formal B(+I)/B(+III) mixed valence system, in the aromatic six-membered B2C2N2 ring.

No MeSH data available.