SYNTHESIS, STRUCTURE, AND MAGNETIC-PROPERTIES OF A NEW LAMELLAR IRON PHOSPHONATE, FEII(C2H5PO3).H2O

A prolonged reaction between the lamellar iron oxychloride FeOCl and ethylphosphonic acid in acetone leads to a new lamellar iron phosphonate, Fe(II)(C2H5PO3).H2O. It crystallizes in space group P1n1 (Z = 2) with parameters a = 4.856(8) angstrom, b = 10.33(1) angstrom, c = 5.744(3) angstrom, beta = 91.0(1)degrees. The lamellar structure consists of roughly coplanar layers of iron atoms coordinated octahedrally by five phosphonate oxygen atoms and one water molecule. Mossbauer parameters agree with values given for Fe2+ in a high-spin state (isomer shift IS = 1.23 mm s-1). Magnetic susceptibility measurements on a powdered sample shows the compound to be a nearly two-dimensional antiferromagnet with field-induced weak ferromagnetism below T(c) = 24.5 K, which is probably due to spin canting.