In this paper, the chemistry of 3-X-1,2-closo-C2B10H11 (X = halogen) derivatives is extended. Molecular orbital and 11B and 13C NMR calculations on these species are presented. A qualitative interpretation of the 11B NMR spectra of closo o-carborane derivatives is also provided. The synthesis of 3-X-1-R-o-carborane (X = I, Br and R = Me, Ph) derivatives is reported, and aryldehalogenation at the B3 position is reported for the first time. The molecular and crystal structures of 1-phenyl-3-bromo- 1,2-dicarba-closo-dodecaborane and 3-phenyl-1,2-dicarba-closo-dodecaborane are described.