SYNTHESIS AND CRYSTAL-STRUCTURES OF ALUMINUM AND IRON PHOSPHITES

The hydrated forms of aluminum and iron phosphite were prepared and their structure was solved using X-ray powder diffraction data. The diffraction data for the aluminum phosphite powder sample was collected using synchrotron radiation (lambda = 1.3087 angstrom) while that for iron phosphite was obtained from a rotating anode X-ray source. Both compounds crystallize in the monoclinic space group, P2(1). Unit cell parameters for the Al compound: a = 8.0941(1), b = 9.9137(1), c = 7.6254(1) angstrom, beta = 111.95-degrees; Fe compound: a = 8.2548(1), b = 10.1814(1), c = 7.7964(1) (angstrom), beta = 111.94(1)degrees. The Rietveld refined formula is M2(PO3H)3.4H2O (M=Al, Fe). There are two independent metal atoms in the structure and both are six-coordinated. One of them is coordinated by two water molecules and four phosphite oxygens. The other atom is surrounded by one water molecule and five phosphite oxygens. All the phosphite oxygens are involved in bridging the Al atoms. The geometry about Al, Fe, and P atoms is normal and they display expected bond parameters. The Lattice water is located in the cavity and is hydrogen bonded to phosphite oxygen and water molecules.