Borabenzene

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]−.

Borabenzene
Names
Preferred IUPAC name
Borinine
Identifiers
3D model (JSmol)
ChemSpider
  • InChI=1S/C5H5B/c1-2-4-6-5-3-1/h1-5H
    Key: HXNZTJULPKRNPR-UHFFFAOYSA-N
  • B1=CC=CC=C1
Properties
C5H5B
Molar mass 75.91 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

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:

C
5H
5N + MeOBC
5H
5SiMe
3 → C
5H
5N-BC
5H
5 + MeOSiMe3

The pyridine adduct C
5H
5N-BC
5H
5 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.

Adducts of borabenzene with pyridine and triphenylphosphine.

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

Borabarrelene synthesis via a Diels-Alder reaction of borabenzene-pyridine adduct

See also

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