Significant coordination changes introduced by substituted pyridines into silver-thiosaccharinate complexes

DENNEHY, MARIANA; QUINZANI, OSCAR V.; BURROW, ROBERT A

Foz do Iguazu, Brasil

Congreso; XIV Brazilian Meeting on Inorganic Chemistry (BMIC2008) and I Latin American Meeting on Biological Inorganic Chemistry (LABIC2008); 2008

Sociedade Brasileira de Quimica

The study of the coordination chemistry of silver(I) with thiosaccharinate (tsac), the anion of thiosaccharine – the thione form of saccharine, C6H4S(O)2NHC(S) – is of interest because of the flexibility shown by the silver(I) coordination sphere and the versatility of the thionate ligand, which can coordinate to metals through different coordination modes [1-3]. Of the ternary systems we have studied, the complex [Ag2(tsac)2py] has stood out due to its very curious structure in which the anions coordinate to the silver centers in a “head to head” conformation [4]. This result prompted us to study the effect of substitutents in the pyridine ring on the coordination of the base to the Ag-tsac system. The substituted pyridines used in this study were 3-methylpyridine (3-pic), 4-methylpyridine (4-pic), 4-methoxypyridine (4-MeOpy) and quinoline (quin). The four novel crystalline complexes from these pyridine ligands show quite different structures. Three of them are coordination polymers. The tsac ligands bridge Ag centers, bonding via both the S and N atoms in complexes [Ag2(tsac)2(4-pic)]n 1 and [Ag2(tsac)2(quin)2] 2. The first shows a “head to head” conformation of the tsac ligands while the last, a “head to tail” conformation. In [Ag2(tsac)2(MeOpy)2] 3, the two independent tsac ligands bond differently to the Ag atoms. One tsac ligand chelates with the S and N atoms to only one Ag center, while the other chelates to the other Ag center and also bridges the two Ag centers with its S atom. All three have short Ag–Ag distances. In [Ag(tsac)(3-pic)2]n 4, the tsac ligand bridges between Ag centers with its S atoms. There is no Ag∙∙∙Ag interaction. The complexes were fully characterized by elemental analysis, IR spectroscopy and their crystal structures were solved by X-ray diffraction