Alkali metal-based reagents have been utilized in chemical transformations to generate strong carbon-centered nucleophiles in synthetic organic and inorganic chemistry. The uncompensated negative charge on the carbon atom in these separated ion pairs provides increased nucleophilicity becoming interesting species to be studied in synthetic organometallic chemistry. Carboranes are icosahedral molecular clusters made of carbon and boron atoms. The highly electron delocalized character in this 3-D cage has increased the stability of this molecule while the steric and electronic properties of the cluster along with the selective functionalization of the B-H and C-H bonds have made it an attractive multifunctional ligand in organometallic chemistry. The functionalization of the carborane cage via carbon atoms is carried out through nucleophilic substitution reactions. The deprotonation of the acidic C-H groups in the carborane cage is done by strong alkali bases. These metalated carborane cages are seldomly isolated, nevertheless reacted with electrophiles. In this work, the metal component of the deprotonated carborane carbon was separated from the cluster using metal-chelating crown ethers to report for the first time in literature the isolation, structural and spectroscopic characterization of the highly nucleophilic “naked” 3-D carborane carbanion without charge compensation. Analogously, the doubly deprotonated 1,1′-bis(o-carborane) yielded the dianionic species denoting the first example of dicarbanion.

Synthesis, isolation, and characterization of three-dimensional carborane carbanions

ACS Fall 2021

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