Synthesis and structural characterization of two new polynuclear metal thiosaccharinates: Hexakis(thiosaccharinato)hexasilver(I) and tetrakis(thiosaccharinato)tetracopper(I)

The title compounds, for short Ag6(tsac)6 (1) and [Cu4(tsac)4(MeCN)2] · 2MeCN (2), were prepared by the reaction of thiosaccharin with Ag(I) or Cu(II) salts in different solvents. The new complexes were characterized by FT-IR, Raman, UV–Vis and NMR spectroscopy. Their crystal and molecular structures were determined by X-ray diffraction methods. The structures were solved from 1621 (1) and 7080 (2) reflections with I > 2σ (I ) and refined to agreement R1-factors of 0.0261 (1) and 0.0456 (2). Ag6(tsac)6 molecule derives from the clustering of six Ag(tsac) moieties related to each other through the crystallographic 3-bar (S 6) symmetry operations of the View the MathML sourceR3¯ space group. This results in a highly regular molecular structure where the silver atoms are at the corners of an octahedral core slightly compressed along one of its three-fold axis [inter-metallic Ag⋯Ag contacts of 3.1723(4) and 3.1556(4) Å]. The six thiosaccharinate ligands bridge neighboring Ag atoms along the C3-axis through Ag–N bonds [d(Ag–N) = 2.285(2) Å] at one end and bifurcated Ag–S(thione)–Ag bonds [Ag–S distances of 2.4861(7) and 2.5014(8) Å] at the other end. In contrast, the 2 compound is arranged in the lattice as an irregular tetrameric copper complex [Cu4(tsac)4(MeCN)2] where the metals show different environments. Two copper ions are four-fold coordinated to three tsac ions through the N-atom of one tsac [Cu–N distances of 2.112(3) and 2.064(3) Å] and the thione sulfur atom of the other two [Cu–S distances in the range from 2.284(1) to 2.358(1) Å] and to a MeCN solvent molecule [Cu–N distances of 1.983(4) and 2.052(3) Å]. The other two copper ions are in three-fold environment, one trans-coordinated to two tsac ions [Cu–N distances of 1.912(3) and 1.920(3) Å] and to the thione S-atom of a third ligand [d(Cu–S) = 2.531(1) Å], the other one to the thione sulfur atom of three tsac ligands [Cu–S distances in the range from 2.229(1) to 2.334(1) Å]. The clustering renders the metals to short distances from each other, the shorter Cu⋯Cu distance being 2.6033(7) Å, as to presume the existence of weak inter-metallic interaction within the cluster.