[Li2(tF‐BDC)(DMF)2]: A New Alkali Metal Salt of Tetra­fluoroterephthalic Acid (H2tF‐BDC)

AbstractThe DMF solvate of lithium tetrafluoroterephthalate [Li2(tF‐BDC)(DMF)2] (H2tF‐BDC = tetrafluoroterephthalic acid) was synthesized and structurally characterized from X‐ray single crystal data (Pbcn, Z = 8). Li+ (CN = 4) is coordinated tetrahedrally by four oxygen atoms of three different tF‐BDC2– linkers and one DMF molecule. The LiO4 tetrahedra are connected by common vertices to chains, which are bridged by tF‐BDC2– linkers to form a 2D polymeric unit. The DMF molecules are oriented perpendicular to these polymeric sheets, which are stacked along [100] in an AB fashion and held together by weak van der Waals interactions. Single crystals of [Li2(tF‐BDC)(DMF)2] were synthesized by precipitation from an ethanol/DMF solvent mixture, but single‐phase samples were only obtained by a mechanochemical approach starting from lithium acetate and H2tF‐BDC by adding DMF. The thermal stability of [Li2(tF‐BDC)(DMF)2] was investigated by DTA/TG measurements. The (endothermic) decomposition starts at 170 °C and is followed by a second exothermic decomposition at approx. 300 °C. The weight losses are in good agreement with a release of DMF and CO2. LiF is identified in the residue after heating at 500 °C.