The syntheses of macrocyclic species composed of carborane derivatives joined via their carbon vertices by electrophilic mercury atoms are described. The reaction of closo-1,2-Li-2[C(2)B(10)H(10-x)R(x)] with HgI2 gives Li-2[(1,2C(2)B(10)H(10-x)R(x)Hg)(4)I-2] [R = Et, x = 2 (5 . I2Li2); R = Me, x 2 (6 . I2Li2); R = Me, x = 4 (7 . I2Li2)]. 6 . I-2(K .[18]dibenzocrownd-6)(2) crystallizes in the monoclinic space group C2/m [a = 28.99(2) Angstrom, b = 18.19(1) Angstrom, c 13.61(1) Angstrom, beta = 113.74(2)degrees, V = 6568 Angstrom(3), Z = 4, R = 0.060, R(w) = 0.070]; 7 . I-2(NBu(4))(2) crystallizes in the monoclinic space group P2(1)/c [a = 12.77(1) Angstrom, b = 21.12(2) Angstrom, c 20.96(2) Angstrom, beta = 97.87(2)degrees, V = 5600 Angstrom(3), Z = 2, R 0.072, R(w) = 0.082]. The precursor to 7, close-8,9,10,12-Me(4)-1,2-C2B10H8 (4), is made in a single step by reaction of closo-1,2-C2B10H12 With MeI in trifluoromethanesulfonic acid : The free hosts 5, 6, and 7 are obtained by reaction of the iodide complexes with stoichiometric quantities of AgOAc. A Hg-199 NMR study indicates that sequential removal of iodide from 5 . I2Li2 and 6 . I2Li2 with aliquots of AgOAc solution leads to formation of two intermediate host-guest complexes in solution, presumed to be 5(6)ILi and 5(2)(6)(2) . ILi. Crystals grown from a solution of 6 . I2Li2 to which 1 equiv of AgOAc solution had been added proved to be an unusual stack structure with the formula 6(3) . I4Li4 [tetragonal, 14/m, a = 21.589(2) Angstrom, c 21.666(2) Angstrom, V = 10098 Angstrom(3), Z = 2, R = 0.058, R(w) = 0.084]. Addition of 2 equiv of NBu(4)Br ion to 5 or 6 gives 5 . Br-2(NBu(4))(2) and 6 . Br-2(NBu(4))(2), respectively, while addition of 1 equiv of KBr to 6 forms 6 . BrK. 5 . Br-2(NBu(4))2 crystallizes in the triclinic space group P<(1)over bar>, [a = 10.433(1) Angstrom, b = 13.013(1) Angstrom, c 15.867(2) Angstrom, alpha = 91.638(2)degrees, beta = 97.186(3)degrees, gamma = 114.202(2)degrees, V = 1492 Angstrom(3) Z = 1, R = 0.078, R(w) = 0.104]. The hosts 5 and 6 form 1:1 supramolecular adducts with the polyhedral amons B10I102- and B12I122- in solution.