Host-Guest Chemistry of a New Class of Macrocyclic Multidentate Lewis Acids Comprised of Carborane-Supported Electrophilic Mercury Centers

Xiaoguang Yang, Carolyn B. Knobler, Zhiping Zheng, M. Frederick Hawthorne

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Abstract

The synthesis and characterization of a family of carborane-supported macrocycles containing electrophilic mercury centers is described. These compounds are multidentate Lewis acids which have been demonstrated to bind anions such as CI-, Br, I-, and closo-B10H102- as well as uncharged nucleophilic species. The lithium salts of the anionic complexes [(l,2-C2B10H10Hg)4Xn]Lin(1.XnLin; X = CI, Br, n = 1; X = I, n = 1 or 2) were synthesized from the reaction of closo-1, 2-Li2-1,2-C2B10 H10 with HgX2 (X = CI, Br, and I) in 70-80% yields. The free host [12]mercuracarborand-4 (1) was obtained by the removal of halide ions from 1·122- with AgOAc. The molecular structures of 1-ClLi, (1-Br)2-(benzo[15]crown-5)3.Li2(H2O)2, and 1-I2(AsPh4)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) Å, c = 11.2641(7) Å,V= 2311 Å3, Z = 2 (1/8 of the tetramer per asymmetric unit), R = 0.041, Rw = 0.060. (1-Br)2 (dibenzo[15]crown-5)3.Li2(H2O)2crystallizes in triclinic space group P1, a = 11.3204(4) Å, b = 22.7459(8) Å, c = 27.8148(9) Å, α = 86.5346(9)°,β = 86.218(1)°, γ = 88.640(1)°, V = 7132 Å3, Z = 2, R = 0.039, Rw = 0.050. 1·I2(AsPh4)2 crystallizes in monoclinic space group P21/n, a = 9.518(2) Å, b = 30.516(6) Å, c = 15.531(4) Å, β = 99.331(6)°, V= 4451 Å3, Z - 2, R = 0.045, Rw = 0.053. The structures and bonding observed in these complexes of host 1 are discussed. A 199Hg NMR spectroscopic study demonstrated that 1·I- and 1·I22- were formed upon the sequential addition of iodide ion to an acetone solution of 1. An octaethyl derivative of 1 was synthesized from [(l,2-C2B10H8Et2Hg)4-I2]Li2 (2a·I2Li2), which was originally obtained from the reaction of closo-l,2-Li2-9,12-Et2-l,2-C2B10H8 with Hgl2. 2a crystallizes in tetragonal space group P421c, a = 14.806(1) Å, c = 13.5141(9) Å, V= 2962 Å3, Z = 2, R = 0.052, Rw = 0.058. The absence of coordinating solvents allows the formation of supramolecular species 2a-(9-I-12-Et-l,2-C2B10H10)2 and 2a-(9,12-I2-l,2-C2B10H10)2, the former of which crystallizes in the monoclinic space group P21/c, a = 12.828(1) Å, b = 22.650(2) Å, c = 14.698(1) Å, β = 108.541(2)°, V = 4049 Å3, Z = 2, R - 0.059, Rw = 0.059 and the latter of which crystallizes in P21/c, a = 12.768(2) Å, b = 22.907(4) Å, c = 14.589(3) Å, β = 108.202(3)°, V = 4053 Å3, Z = 2, R - 0.064 Rw = 0.081. In addition, molecular aggregates of closo-B10H102- (10) with 1 and 2a were studied. 2a-102(MePh3P)4 crystallizes in the triclinic space group P1, a = 15.583(2) Å, b = 15.861(2) Å, c = 16.045(2) Å, α = 67.831(4)°, β = 70.713(4)°, γ = 86.371(4)°, V = 3457 Å3, Z = 1, R = 0.056, Rw = 0.064. The template effect observed in the synthesis of the mercuracarborand hosts is discussed, along with the structures and bonding present in the host-guest complexes mentioned above.

Original languageEnglish (US)
Pages (from-to)7142-7159
Number of pages18
JournalJournal of the American Chemical Society
Volume116
Issue number16
DOIs
StatePublished - Aug 1 1994

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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