Mercury(II) compounds with 1,3-benzothiazole-2-thione. Spectral, thermal, and crystal structure studies

Mercury(II) halides, HgX2 (X = Cl-; Br-; I-) react with 1,3-benzothiazole-2-thione (btztH) in methanol solutions giving the HgX2(btztH) and HgX2(btztH)(2) types of compounds. Mercury( II) acetate gives the thiolato compound Hg(btzt)(2) because of the deprotonation of btztH. Hg(btzt)(2) reacts with 2,2'-bipyridine (bipy) giving a 1: 1 complex. IR, H-1, and C-13 NMR spectral studies indicate that btztH acts as a monodenatate ligand through the S thione donor atom in all complexes. The X-ray crystal structure determinations of [HgI2(btztH)](2), HgBr2( btztH)(2), Hg(btzt)(2), and Hg(btzt)(2)(bipy) have been carried out revealing tetrahedrally coordinated mercury atom in [HgI2( btztH)] 2 and HgBr2(btztH)(2), while in Hg(btzt)(2)(bipy) 2 + 2 coordination is achieved through strong Hg...(N( bipy) contacts. A linear coordination in Hg(btzt)(2) is not affected by the Hg...N contacts, which are longer than in Hg(btzt)(2)(bipy), but still shorter than the van der Waals sum of mercury and nitrogen covalent radii. [HgI2(btztH)](2) exists as centrosymmetrical dimer with a Hg2I2 bridging core. The dimeric molecules are linked by the intermolecular hydrogen bonds between the terminal iodine atom and the NH group [3.63(1) Angstrom] into infinite chains along the z-axis. There are N-H...Br(bridging) intermolecular hydrogen bonds in HgBr2( btztH) 2 joining molecules into endless chains along the x-axis. The Br(bridging) atom acts as double proton acceptor and two NH groups as proton donors [NH...Br( bridging) 3.278(9) and 3.338(7) Angstrom]. The mercury to sulfur and mercury to halogen bond distances in [HgI2( btztH)](2) and HgBr2( btztH)(2) are discussed in relation to the analogous compounds, revealing strong influence of hydrogen bonds on their relative strengths as well as crystal packing requirements of the ligand. The sulfur and halogen atoms are more tightly bound to mercury implicating severe distortion of the coordination polyhedron in the structures in which they do not take part in hydrogen bonds formation. The influence of steric requirements of the ligands in Hg(btzt)(2) and Hg(btzt)(2)( bipy) on the distortion of the mercury coordination polyhedra accompanied with the relative strength of Hg...N contacts is considered.