Borabenzene

Unlike the related but highly stable benzene molecule, borabenzene would be electron-deficient.

Related derivatives are the boratabenzene anions, including the parent [C5H5BH]−.

4-Silyl-1-methoxyboracyclohexadiene is used as a precursor to the borabenzene: The pyridine adduct C5H5N-BC5H5 is structurally related to biphenyl.

[1] It is a yellow whereas biphenyl is colorless, indicating distinct electronic structures.

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

Adducts of borabenzene with pyridine and triphenylphosphine.