Structural Diversity of Silver Fluorinated β-Diketonates: Effect of the Terminal Substituent and Solvent

In order to demonstrate the role of the fluorination and some solvents in the structural organization of the Ag(I) coordination polymers with β-diketonate ligands (R¹C(O)C_αHC(O)R²)^- we synthesized a series of the compounds containing tfac- (R₁ = CH₃, R² = CF₃) and pfpac- (R₁ = CH₃, R² = C₂F₅) anions. Solvent-free [Ag(L)]_∞ (L = tfac 1, pfpac 2) compounds and the corresponding acetonitrile and toluene adducts have been characterized by elemental analysis and/or NMR, IR and single-crystal XRD. This series includes five new coordination polymers. Compound 1 is a 3D coordination framework based on Ag-O_{chelate/bridge}, Ag-C_α bonds, and argentophilic interactions. An increase in the fluorinated group leads to a chain coordination polymer 2 of an unusual structural organization. These chains can be represented as a "DNA-type", where two intertwined helices based on Ag-O_chelate and Ag-C_α bonds are connected through Ag-O_bridge ones. Two structural types of chain coordination polymers, [Ag(tfac)(CH₃CN)] and [Ag₂(L)₂(solvent)], have been revealed for the adducts. The latter structural type differs significantly from the previously studied toluene and acetonitrile adducts of fluorinated Ag(I) β-diketonates of the same stoichiometry. Thermal analysis in helium showed that both 1 and 2 decompose to metallic silver with the compound of pfpac-ligand being slightly more stable.