Crystal Structure, Electronic Structure, and Temperature-Dependent Raman Spectra of Tl[Ag(CN)2]: Evidence for Ligand-Unsupported Argentophilic Interactions

The structure of thallium dicyanoargentate(T) has been determined crystallographically. The crystal structure shows an Ag-Ag distance of 3.11 Å. This is the shortest Ag-Ag distance reported for any silver dicyanide salt whose crystal structure has been determined. Raman spectra of the compound show four νC-N peaks that are well-resolved in the 10-80 K temperature range. This result agrees well with group theory analysis. Extended Hückel calculations using relativistic wave functions have been carried out for two models which describe the interactions between the Ag(CN)2- ions within the crystal structure of Tl[Ag(CN)2]. The results of these calculations indicate the formation of potential wells at short Ag-Ag distances. The data in this study suggest the significance of ligand-unsupported silver-silver interactions (argentophilicity) in Tl[Ag(CN)2]. Tl-Ag interactions are determined to be insignificant in the compound. Tl[Ag(CN)2] crystallizes in the monoclinic space group P21/c (No. 14), with a = 7.798(1) Å, b= 14.685(3) Å. c = 8.566(2) Å, β= 91.66(2)°, Z = 8, R = 0.0643, and Rw = 0.0899.