Structure-directing influence of halide in mercury thiolate clusters

Under identical conditions, the reaction of 2-aminoethanethiol hydrochloride with HgX2 (X = Cl and Br) in water yielded discrete hexanuclear [Hg6Cl8(SCH2CH2NH3)(8))]Cl-4 center dot 4H(2)O (1) and nonanuclear [Hg9Br15(SCH2CH2NH3)(9)](Cl-0.8-Br-0.2)(3) (2) complexes with unusual coordination environments. Compound 1 crystallizes as triclinic with a = 9.434(2) angstrom, b = 10.999(2) angstrom, c = 13.675(7) angstrom, alpha = 92.9(7)degrees, beta = 105.2(7)degrees, and gamma = 96.9(7)degrees, whereas 2 is monoclinic with a = 14.162(3) angstrom, b = 8.009(16) angstrom, c = 19.604(4) angstrom, alpha = gamma = 90.0 degrees, and beta = 92.7(3)degrees. In both cases, it is observed that the halide creates the secondary structure around trinuclear units (dimer in 1 and trimer in 2) through Hg-X bonding. Two independent types of Hg atoms (four- and five-coordinate in 1) and (three- and four-coordinate in 2) are observed. The geometry around Hg is quite variable with bridging thiolate and both bridging and terminal halides. The angles around Hg associated with the S atoms are more obtuse than expected from mercury(II) thiolates with a coordination number of more than 2. Intermolecular hydrogen bonding involving Nh(3)(+), water molecules, and the halide atoms is responsible for the three-dimensional network in both compounds. Relatively short Hg center dot center dot center dot Hg interactions in 1 (3.797 and 3.776 angstrom) and in 2 (3.605 and 3.750 angstrom) are also observed. The compounds have been characterized with the help of H-1 and C-13 NMR, UV-Vis, infrared, Raman, and mass spectrometry, thermogravimetric analysis, and single X-ray crystallography.