Synthesis of Halogen-Substituted [12]Mercuracarborands-4. Crystal Structure of {[(9,12-I<sub>2</sub>-C<sub>2</sub>B<sub>10</sub>H<sub>8</sub>-1,2-Hg)<sub>4</sub>]Cl}Na(H<sub>2</sub&

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-C2B10H8-1,2ʹ-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.