An X-ray diffraction study of anion and ratio dependence in the formation of discrete molecules versus polymeric arrays involving silver salts and bipyridine ligands

Described are the reaction of the silver(I) salts of trifluoroacetate (tfa⁻) and trifluoromethanesulfonate (Otf⁻) with the bidentate ligands 4,4′-dimethyl-2,2′-bipyridine (L1), 5,5′-dimethyl-2,2′-bipyridine (L2) and 2,2′-bipyridine (L3), to afford the formation of five structures. A systematic study was conducted to obtain the different coordination moieties possible by changing the ligand to metal ratio and the solvent of crystallization. In total, six discrete molecules (Agtfa)(L1), 1, (Agtfa)(L2), 2A and 2B, (AgOtf)₂(L2)₃, 3A and 3B, (AgOtf)₂(L3)₃, 5, and one polymeric structure (AgOtf)(L3)_n, 4 were obtained. Compounds 2 and 3 form two crystal structures each, where differences in connectivity of the corresponding anion to the metal center are observed, as directed by solvent of crystallization. The varying degree of interaction of the two anions, combined with the functionality of the ligand used in the reaction, gave rise to coordination numbers from 4 to 6, representing capped-trigonal, distorted tetrahedral, trigonal bipyramidal and distorted octahedral environments, which illustrate the range of coordination moieties that can be adopted in silver(I) complexes, and the possibility of systematic control of the coordination framework topology of a compound. This study complements the already reported silver coordinated structures associated with the bipyridine ligands mentioned herein.