Anion- and solvent-directed assembly in silver bis(thioimidazolyl)methane chemistry and the silver-sulfur interaction

The effect of metal complexation on the structure and properties of the electroactive bis(1-methylthioimidazolyl)methane linkage isomers CH2(N-tim)2 (L1) and CH2(S-tim)2 (L2) has been explored. Coordination polymers {[Ag(L1)2]X}n (X = BF4, PF6) are formed by bridging L1 between tetrahedral silver centers giving two-dimensional cationic sheets composed of AgS(4) linkages; the anions are sandwiched between sheets. Cyclic dimers {[Ag2(L2)2]X2} (X = BF4, PF6, OSO2CF3) are formed when L2:AgX ratios are lower than 1.5. When L2:AgPF6 was 1.5 or higher, the complex [Ag4(L2)5](PF5)4 could be isolated as a solvate. The NMR, IR, electrochemical, and ESI+ mass spectral data of this latter compound indicate that extensive dissociation to the cyclic dimer and free ligand occurs in solution. Finally, a Cambridge Structural Database search was performed to provide insight into reasonable silver-sulfur bond distances, since literature values appeared to vary widely between 2.3 and 3.2 A. It was found that these distances increase with increasing coordination number of silver. The average distances for 2-, 3-, 4-, 5-, and 6-coordinate silver were found to be 2.40, 2.52, 2.62, 2.70, and 2.75 A, respectively.