Synthesis of Halogen-Substituted [12]Mercuracarborands-4. Crystal Structure of {[(9,12-I₂-C₂B₁₀H₈-1,2'-Hg)₄]Cl}Na(H₂O)_n

The reactions of the dilithium derivatives of 9,12-dihalogen-ortho-carboranes 1,2-Li₂-C₂B₁₀H₈-9,12-X₂ (X = Cl, Br, I) with mercury chloride HgCl₂ afford a number of complexes of the chloride ion with the halogen derivatives of [12]mercuracarborand-4: {[(9,12-X₂-C₂B₁₀H₈-1,2'-Hg)₄]Cl}Na·nH₂O. The molecular crystal structure of the complex of the [12]mercuracarborand-4 octaiodine derivative with the chloride ion is determined by X-ray diffraction. The substituents at the periphery of the mercury-containing macrocycle are found to exert a substantial effect on the macrocycle geometry leading to the transition from the planar to butterfly conformation, whose geometry is predetermined by a set of intermolecular interactions in the crystal.