Synthesis of Functional Derivatives of 7,8-Dicarba-nido-undecaborate Anion by Ring-Opening of Its Cyclic Oxonium Derivatives

A new approach to synthesis of functional derivatives of 7,8-dicarba-nido-undecaborate anion based on ring-opening of its cyclic oxonium derivatives [10-(CH2)4O-7,8-C2B9H11] and [10-O(CH2CH2)2O-7,8-C2B9H11] with various nucleophiles was developed. Both cyclic oxonium derivatives can be obtained as single isomers by reaction of the parent anion [7,8-C2B9H12]- with mercury(II) chloride in the corresponding solvents. Mechanism of formation of the cyclic oxonium derivatives of 7,8-dicarba-nido-undecaborate anion was proposed. A series of 7,8-dicarba-nido-undecaborate derivatives with terminal carboxylic and azide functions were prepared by the ring-opening reactions of the cyclic oxonium derivatives with substituted phenolate and azide ions, respectively.