STRUCTURE AND BONDING OF A NOVEL MERCURACYCLE COMPLEX CONTAINING B-HGBONDS AT CARBARONE VERTICES

The known compound 9-CF3CO2Hg-1,7-C2B10H11, 3, was obtained by direct mercuration of 1,7-C2B10H12 (m-carborane) with 1 equiv of mercuric oxi de in trifluoroacetic acid. Species 3 has now been fully characterized by multinuclear NMR and mass spectroscopy. A byproduct, 4, [(1,7-C2B1 0H10)2Hg4(OH)2][CF3CO2]2, obtained from the reaction mixture was found in the solid state to be a cyclic array containing four mercury cente rs in which four trifluoroacetate anions interact simultaneously with each macrocycle. Two CF3CO2- ions form a pair of hydrogen bonds with t he (OH) ligands present in the macrocycle skeleton, and the remaining two trifluorocetate anions interact with the cycle via moderately stro ng electrostatic interactions between Hg atoms and the oxygen atoms of the carboxylate groups. Each of the four trifluoroacetate anions is s hared by two macrocycles to form a self-assembled 1:2 (mercury cycle t o trifluoroacetate ion) polymeric array. Crystallographic data are as follows: triclinic, space group P1BAR, a = 10.6113(8) angstrom, b = 11 .1127(9) angstrom, c = 7.2044(5) angstrom, alpha = 74.826(2)-degrees, beta = 78.473(2)-degrees, gamma = 72.591(2)-degrees, V = 775.53 angstr om3 Z = 1, sigma(calcd) = 2.88 g cm-3, R = 0.049, R(w) = 0.058.