SYNTHESIS AND PROPERTIES OF HEXACYANOFERRATE INTERLAYERED IN HYDROTALCITE .1. HEXACYANOFERRATE(II)

Hydrotalcite (HT) interlayered with hexacyanoferrate(II) ions ([Mg4.62 Al1.52(OH)12][(Fe(CN6)0.30(CO3)0.29]) has been synthesized from the ca rbonate-HT ([Mg4.52Al1.50(OH)12][(CO3)0.77]) through double ion exchan ge reactions, and the products have been studied by chemical and physi cal methods. Mossbauer spectroscopy shows that hexacyanoferrate(II) is held rigidly in the interlayer by electrostatic forces and is charact erized by a singlet at 0.01 mm s-1 at 80 K. X-ray diffraction shows an increase of the basal spacing (d003) from 0.78 to 1.1 nm following ex change. Hexacyanoferrate(II) in the interlayer was oxidized to hexacya noferrate(III) (up to 20%) by dioxygen on dehydrating the interlayer e ither by drying at 70-degrees-C or by washing with nonaqueous solvents like acetone or ethanol. The CN (nu6) band of hexacyanoferrate(II) an d (III) is found at 2036 cm-1 and 2112 cm-1, respectively. The presenc e of an absorption band at 2080 cm-1, assigned to free cyanide anions in the interlayer, suggests that the hexacyanoferrate(II,III) complexe s are not inert in the interlayer, cyanide ligands being substituted w ith either water or hydroxyls. Oxidation and ligand exchange of the he xacyanoferrate(II) are also indicated by Mossbauer spectroscopy.