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

The DMF solvate of lithium tetrafluoroterephthalate [Li 2 (tF‐BDC)(DMF) 2 ] (H 2 tF‐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‐BDC 2– linkers and one DMF molecule. The LiO 4 tetrahedra are connected by common vertices to chains, which are bridged by tF‐BDC 2– 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 [Li 2 (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 H 2 tF‐BDC by adding DMF. The thermal stability of [Li 2 (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 CO 2 . LiF is identified in the residue after heating at 500 °C.