Synthesis and Physico‐Chemical Studies on Iron(II,III,III) and Cobalt(II) Thiocarboxylates

Abstract

A series of iron(II,III,III) and cobalt(II) complexes of thiocarboxylic acids of the general formulas [Fe^IIFe₂ ^IIIO(SOCR)₆(L)₃] and [Co(SOCR)₂(L)₂] (R = C₂H₅ or C(CH₃)₃ and L = EtOH or py) have been synthesized and characterized by elemental and thermogravimetric analyses, spectral (infrared, electronic, and Mössbauer) studies, molar conductance, magnetic susceptibility, and molecular weight determinations. The electronic spectral data suggested an octahedral environment around the metal ion in both the iron as well as the cobalt complexes. A band around 13,800 cm⁻¹ in the electronic spectra of the iron complexes indicated intervalence‐transfer between Fe(II) and Fe(III) moieties. A bridging mode of coordination could be assigned for the thiocarboxylate anions in the iron complexes and a chelating mode of coordination for the cobalt complexes have been suggested by infrared spectral data along with a new band at 540 cm⁻¹, which may be ascribed owing to ν_asy(Fe₃O) vibrations. Mössbauer studies revealed two resolved quadrupole doublets at 120–315 K confirming the presence of Fe(II) and Fe(III) moities in the iron complexes. Thermoanalytical data indicated the iron complexes were thermally stable up to 135 °C, whereas the cobalt complexes were stable up to 160 °C, above which temperature decomposition started and continued to ∼400 °C at which temperature the formation of metal sulfide and/or oxide was noticed. An attempt has been made to establish the structures based on these studies.

Keywords:

• Thiocarboxylates
• Mixed‐valence iron complex
• Oxo‐bridged
• Cobalt(II) complex

Acknowledgments

Financial support from the University Grants Commission, New Delhi, is thankfully acknowledged. One of us (TG) thanks to the Council of Scientific and Industrial Research, New Delhi, for the award of Senior Research Fellowship.