1:1 and 1:2 complexes of mercury(II) halides with 1,3-thiazolidine-2-thione.: Spectral, thermal, and crystal structure studies

The series of compounds of the general formulae HgX2(tzdtH) and HgX2( tzdtH)(2) (X = Cl, Br, I; tzdtH D 1,3-thiazolidine-2-thione) have been prepared, as well as Hg(tzdt)(2). IR, H-1, and C-13 NMR spectral data of the complexes indicate thione donation, which is confirmed by the crystal structure analyses of [HgBr2(tzdtH)](2), [HgI2(tzdtH)](2), and HgI2( tzdtH)(2). The structures of [HgBr2(tzdtH)](2) and [HgI2(tzdtH)](2) consist of centrosymmetric doubly bridged dimers, but they are not isostructural. The asymmetry in the HgX2Hg bridge is more pronounced in the bromo than in the iodo derivative [S-Hg-X( terminal) is 138.19(9)degrees for X = Br and 123.49(10)degrees for X = I], which is accompanied by the stronger Hg-S covalent bond in the bromo than in the iodo complex [2.435(4) vs. 2.510(3) Angstrom]. The Hg-X(bridging) (X = Br, I) bond distances are shorter than the sum of van der Waals radii for mercury and X. Dimeric centrosymmetric complex units are held together only by van der Waals forces in [HgI2(tzdtH)](2), while in [HgBr2( tzdtH)](2) there is an intramolecular hydrogen bond of N-H...Br type (3.34(1) Angstrom). HgI2(tzdtH)(2) exists as a mononuclear tetrahedral complex with two long Hg-S [2.672(1) Angstrom] and two short Hg-I bond distances [2.688(1) Angstrom] related by a twofold axis. The molecules of HgI2(tzdtH)(2) are linked into infinite chains along the c axis by intermolecular N-H...S [3.38(1) Angstrom] hydrogen bonds.