BCsp2

BCsp2 is a designation used in chemistry to describe a boron–carbon fragment in which the carbon center is sp2-hybridized. The fragment typically occurs within a larger molecule or as a reactive intermediate, with boron bonded to a planar, trigonal carbon. The boron atom often has an empty p orbital, imparting Lewis acidic character to the fragment and enabling interactions with nucleophiles or π-systems.

Structurally, the BCsp2 fragment is embedded in a larger framework and features a B–C single bond with the carbon atom in a planar environment. Bond lengths vary with substitution but commonly fall in the range of roughly 1.50–1.60 angstroms for B–C links, reflecting partial π-character and adjacent unsaturation.

Occurrence and formation: BCsp2 motifs arise in synthetic organoboron reagents, during borylation or dehydrohalogenation steps, and as fragments in computational analyses. In experiments, such fragments are typically stabilized by adjacent substituents or by coordination to Lewis bases or metals.

Reactivity: The electron-deficient boron center makes BCsp2 fragments Lewis acidic and capable of undergoing electrophilic additions, cycloadditions, or transmetalation steps within catalytic cycles. Substituents and the electronic environment strongly influence their stability and reactivity.

Computational use: In density functional theory and reaction-network studies, BCsp2 fragments serve as simplified models to explore binding, reactivity, and energy landscapes of larger organoboron systems.

See also: organoboron chemistry, sp2 hybridization, boron-doped carbon materials.