Synthesis, Mossbauer, infrared spectroscopic and thermal decomposition studies of some iron(III) carboxylate complexes

Abstract

Several new iron(IlI) carboxylate complexes with the general formula Na₃[Fe(OCOR)₆]where R = (CH₃)₃C-, CH₃(CH₂)₅, CH₃(CH₂)₁₀-, 2,5-CI₂C₆H₃<i> -, </i>2,5-(CH₃)₂C₆H₃]-,2-MeOC₆H₄- and 3-MeOC₆H₄- have been synthesized. Also, iron(III) complexes with pyridine 2,6-dicarboxylic acid and quinic acid have been synthesized. Infrared data suggest unidentate nature of the carboxylate ligands in all cases. Mossbauer spectra of all the complexes exhibit quadrupole doublet except for quinic acid complex where a triplet has been observed. Isomer shift (<img src='/image/spc_char/delta1.gif' border=0>) values are in the range 0.58-0.74 mm S^-1 (with respect to sodium nitroprusside as a standard) suggesting iron(III) in high spin state. Quadrupole splitting <i>(</i>∆<i>E</i>_Q<i>) </i> values are in the range of 0.30-2.71 mm s^-1 and its variation is attributed to varying distortions in octahedral geometry. Thermogravimetric (TGA) studies show a single stage, but slow decomposition yielding a mixed sodium iron oxide or sodium ferrate (3Na₂O.Fe₂O₃). Magnetic moment and reflectance spectral data have also been reported.