Synthesis and characterization of four ethylenediamine-templated iron arsenates

Four new ethylenediamine-templated iron arsenates and fluoroarsenates have been hydrothermally synthesized from iron metal, hydrofluoric and arsenic acids, and ethylenediamine. Fe(H2AsO4)(HAsO4)(2). enH(2). H2O (1) is one-dimensional and contains chains, (FeFEF2)-F-III-F-II(HAsO4)(AsO4). enH(2). 2H(2)O (2) is a layered fluoroarsenate, and Fe-3(HAsO4)(6). enH(2). NH3. NH4 (3) and Fe2F2(AsO4)(2)(H2O). enH(2) (4) are an arsenate and a fluoroarsenate, respectively, with three-dimensional open-framework type structures. Compounds 1, 3, and 4 contain Fe(III) only, while 2 is a mixed-valence compound of Fe(III) and Fe(II). The structures were determined from single-crystal X-ray diffraction. Crystal data: (1) P2(1), a = 4.762(1) Angstrom, b = 16.086(3) Angstrom, c = 8.698(2) Angstrom, beta = 90.65(3)degrees, Z = 2; (2) P-1, a = 5.289(1) Angstrom, b = 7.573 (1) Angstrom, c = 8.888(2) Angstrom, alpha = 67.32(3)degrees, beta = 82.77(3)degrees, gamma = 69.76(3)degrees, Z = 1; (3) cue, a = 18.384(3) Angstrom, b = 8.785(1) Angstrom, c = 16.052(2) Angstrom, beta = 111.11(1)degrees, Z = 4; (4) Pbca, a = 10.490(2) Angstrom b = 10.090(2) Angstrom, c = 20.540(4) Angstrom, Z = 8. Strong hydrogen bonding exists between the chains and the layers in I and 2, and between the diprotonated ethylenediamine and the inorganic part of the structures of 1, 2, and 4. The ethylenediamine in 3 is not hydrogen bonded, and as a result it is disordered. The compounds are characterized also by thermogravimetric analysis, infrared spectroscopy, elemental analysis, and magnetic measurements.