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Pure Appl. Chem., 2003, Vol. 75, No. 9, pp. 1157-1164

New discoveries at the interface of boron and carbon chemistries

M. Frederick Hawthorne

Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90024, USA

Abstract: The continued growth of polyhedral borane chemistry is illustrated by the successful synthesis of [closo-B12(OH)12]2 –by the H2O2 oxidation of [closo-B12H12,]2. The hydroxylated species reacts with common organic reagents to produce 12-fold degenerately substituted carboxylate esters, ethers, and carbamate esters. The ether derivatives undergo facile and reversible redox reactions in which the B12 scaffold serves as a one-or two-electron donor giving stable oxidation states described by [closo -or hypercloso-B12OR)12]n with n = −2,−1,and 0. The loss of polyhedral electrons is compensated by back-bonding from the attached ether oxygen substituents. Structural comparisons are presented along with representative reaction chemistry. Derivatives that bear functional groups on the termini of the 12-fold set of substituents provide a vast array of potential applications. To distinguish these new polyfunctional icosahedral species from dendrimers,they have been designated as closomers.