New discoveries at the interface of boron and carbon chemistries

The continued growth of polyhedral borane chemistry is illustrated by the successful synthesis of [closo-B-12(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 B-12 scaffold serves as a one- or two-electron donor giving stable oxidation states described by [closo- or hypercloso-B-12(OR)(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.