The synthesis and characterization of a family of carborane-supported macrocycle containing electrophilic mercury centers is described. These compounds are multidentate Lewis acids which have been demonstrated to bind anions such as Cl-, Br-, I-, and closo-B10H102- as well as uncharged nucleophilic species. The lithium salts of the anionic complexes [(1,2-C2B10H10Hg)(4)X(n)]Li-n(1.X(n)Li(n); X = Cl, Br, n = 1; X = I, n = 1 or 2) were synthesized from the reaction of closo-1,2-Li-2-1,2-C2B10H10 with HgX(2) (X = Cl, Br, and I) in 70-80% yields. The free host [12]mercuracarborand-4 (1) was obtained by the removal of halide ions from 1.I-2(2-) with AgOAc. The molecular structures of 1.ClLi, (1.Br)(2)-(benzo[15]crown-5)(3).Li-2(H2O)(2), and 1.I-2(AsPh(4))(2) have been determined from single-crystal X-ray diffraction studies. 1.ClLi crystallizes in the tetragonal space group P4/mcc, a = 14.3233(8) Angstrom, c = 11.2641(7) Angstrom, V = 2311 Angstrom(3), Z = 2 (1/8 of the tetramer per asymmetric unit), R = 0.041, R(w) = 0.060. (1.Br)(2)(dibenzo[15]crown-5)(3).Li-2(H2O) crystallizes in triclinic space group , a = 11.3204(4) Angstrom, b = 22.7459(8) Angstrom, c = 27.8148(9) Angstrom, alpha = 86.5346(9)degrees, beta = 86.218(1)degrees, gamma = 88.640(1)degrees, V = 7132 Angstrom(3), Z = 2, R = 0.039, R(w) = 0.050. 1.I-2(AsPh(4))(2) crystallizes in monoclinic space group P2(1)/n, a = 9.518(2) Angstrom, b = 30.516(6) Angstrom, c = 15.531(4) Angstrom, beta = 99.331(6)degrees, V = 4451 Angstrom(3), Z = 2, R = 0.045, R(w) = 0.053. The structures and bonding observed in these complexes of host 1 are discussed. A Hg-199 NMR spectroscopic study demonstrated that 1.I- and 1.I-2(2-) were formed upon the sequential addition of iodide ion to an acetone solution of 1. An octaethyl derivative of 1 was synthesized from [(1,2-C(2)B(10)H(8)Et(2)Hg)(4).I-2]Li-2, which was originally obtained from the reaction of closo-1,2-Li-2-9,12-Et(2)-1,2-C2B10H8 with HgI2. 2a crystallizes in tetragonal space group 2(1)c, a = 14.806(1) Angstrom, c = 13.5141(9) Angstrom, V = 2962 Angstrom(3), Z = 2, R = 0.052, R(w) = 0.058. The absence of coordinating solvents allows the formation of supramolecular species 2a.(9-I-12-Et-1,2-C2B10H10)(2) and 2a.(9,12-I-2-1,2-C2B10H10)(2), the former of which crystallizes in the monoclinic space group P2(1)/c, a = 12.828(1) Angstrom, b = 22.650(2) Angstrom, c = 14.698(1) Angstrom, beta = 108.541(2)degrees, V = 4049 Angstrom(3), Z = 2, R = 0.059, R(w) = 0.059 and the latter of which crystallizes in P2(1)/c, a = 12.768(2) Angstrom, b = 22.907(4) Angstrom, c = 14.589(3) Angstrom, beta = 108.202(3)degrees, V = 4053 Angstrom(3), Z = 2, R = 0.064 R(w) = 0.081. In addition, molecular aggregates of closo-B10H102- (10) with 1 and 2a were studied. 2a-10(2)(MePh(3)P)(4) crystallizes in the triclinic space group , a = 15.583(2) Angstrom, b = 15.861(2) Angstrom, c = 16.045(2) Angstrom, alpha = 67.831(4)degrees, beta = 70.713(4)degrees, gamma = 86.371(4)degrees, V = 3457 Angstrom(3), Z = 1, R = 0.056, R(w) = 0.064.