Hydrothermal Synthesis, Structural, and Magnetic Studies of a New Fluoropyrophosphate: BaFeII2P2O7F2

BaFe2(P2O7)F2 has been synthesized hydrothermally (24 h, 700°C). Its structure, determined using room-temperature singlecrystal X-ray diffraction data, is othorhombic (space group Pmmn, No. 59) with cell parameters a=6.878(1) ?, b=11.847(2) ?, c=4.588(1) ?, V=373.9(1) ?3, and Z=2. The reliability factors converge to R1=2.0% and omega R2=5.8% for 1267 unique reflections (I>2sigma(I)). The structure, which is compared to that of the minerals Lawsonite and Henomartinite, consists of octahedra infinite chains [FeO3F]5n-n and P2O7 pyrophosphate linked to generate a three-dimensional framework. M?ssbauer data are consistent with the presence of one Fe2+ site in the high spin state. Magnetic couplings are discussed in terms of superexchange and super-superexchange interactions.