Complexation of ω-thiocaprolactam with heavy metals:: terminal and bridging coordination modes in cadmium and silver compounds

The soft base w-thiocaprolactam (1-azacycloheptane-2-thione, Hthcl) reacts with Cd-II and Ag-I nitrate salts, giving two new coordination complexes, [Cd(NO3)(2)(C6H11NS)(4)] and [Ag-4(C6H11NS)(8)](NO3)(4). The first compound, tetrakis(1-azacycloheptane-2-thione-S)bis(nitrate-O)cadmium(II), presents a slightly distorted octahedral coordination geometry, with two eta(1)-NO3 fragments in a cis arrangement and four Hthcl molecules bonded via the S atom of the thiocarbonyl group; coordination bond lengths involving S atoms range from 2.5768 (19) to 2.6828 (18) Angstrom. The cationic moiety of the silver compound, tetrakis[mu-(1-azacycloheptane-2-thione-S)]tetrakis[(1-azacycloheptane-2-thione-S)silver(I)] tetranitrate, is a centrosymmetric tetranuclear cluster containing eight HthcI molecules, four of which are in terminal positions [coordination distances 2.4850(19) and 2.478 (2) Angstrom], as in the Cd complex, while the other four bridge two metallic ions each, with coordination distances in the range 2.4608 (17)-2.6976 (18) Angstrom.