Borabenzene Explained

Borabenzene is a hypothetical organoboron compound with the formula C₅H₅B. Unlike the related but highly stable benzene molecule, borabenzene would be electron-deficient. Related derivatives are the boratabenzene anions, including the parent [C₅H₅BH]⁻.

Adducts

Adducts of borabenzene with Lewis bases are isolatable. Since borabenzene is unavailable, these adducts require indirect methods. 4-Silyl-1-methoxyboracyclohexadiene is used as a precursor to the borabenzene:

+ → + MeOSiMe₃

The pyridine adduct is structurally related to biphenyl.^[1] It is a yellow whereas biphenyl is colorless, indicating distinct electronic structures. The pyridine ligand is tightly bound: no exchange is observed with free pyridine, even at elevated temperatures.

The borabenzene-pyridine adduct behaves like a diene, not an analog of biphenyl, and will undergo Diels-Alder reactions.^[2]

See also

• 6-membered aromatic rings with one carbon replaced by another group: silabenzene, germabenzene, stannabenzene, pyridine, phosphorine, arsabenzene, stibabenzene, bismabenzene, pyrylium, thiopyrylium, selenopyrylium, telluropyrylium
• Borazine

References

1. 10.1002/cber.19851180431 . Synthese und Strukturuntersuchung von Pyridin-Borabenzol und Pyridin-2-Boranaphthalin . 1985 . Boese . Roland . Finke . Norbert . Henkelmann . Jochem . Maier . Günther . Paetzold . Peter . Reisenauer . Hans Peter . Schmid . Günter . Chemische Berichte . 118 . 4 . 1644–1654.
2. 10.1021/ol061201w . 1-Borabarrelene Derivatives via Diels−Alder Additions to Borabenzenes . 2006 . Wood . Thomas K. . Piers . Warren E. . Keay . Brian A. . Parvez . Masood . Organic Letters . 8 . 13 . 2875–2878 . 16774279.