Hydrothermal synthesis, structural, and magnetic studies of a new fluoropyrophosphate: BaFe2(II)P2O7F2

BaFe2(P2O7)F-2 has been synthesized hydrothermally (24 h, 700 degrees C), I ts structure, determined using room-temperature single-crystal X-ray diffra ction data, is othorhombic (space group Pmmn, No. 59) with cell parameters a = 6.878(1) Angstrom, b = 11.847(2) Angstrom, c = 4.588(1) Angstrom, V = 3 73.9(1) Angstrom(3), and Z = 2, The reliability factors converge to R-1 = 2 .0% and omega R-2 = 5.8% for 1267 unique reflections (I > 2 sigma(I)). The structure, which is compared to that of the minerals La,vsonite and Henomar tinite, consists of octahedra infinite chains FeO3F](n)(5n-) and P2O7 pyrop hosphate linked to generate a three-dimensional framework. Mossbauer data a re consistent with the presence of one Fe2+ site in the high spin stale. Ma gnetic couplings are discussed in terms of superexchange and super-superexc hange interactions. (C) 1999 Academic Press.