Magnetic and spectroscopic investigations of iron and other ..... Ligands

Abstract

The complexes of a new ligand, 2-thioacetamido thiazole (TATZ) with halide and nitrate salts of Fe(II), Ni(II), Cu(I,II), Zn(II), Cd(II) and Hg(II) have been synthesized. The compounds have the general formula, M(TATZ)?·nH?O where X = Cl, Br for Fe(II), Zn(II), Cd(II) and Hg(II); X = Cl for Cu(I) and X = Cl, Br, I, NO? for Ni(II) and Cu(II) with n varying from 0–2. The characterization of the complexes has been accomplished by elemental analysis, molar conductance, electronic, infrared, proton and carbon-13 NMR spectra. The iron complexes have also been studied by Mössbauer spectroscopy. The ligand TATZ was found to act as a monodentate ligand or as a bidentate chelate depending upon the nature of the metal ion. With Zn(II) and Cd(II) ions, TATZ is inferred to coordinate rather unexpectedly as a unidentate ligand bonding through thiazole nitrogen while Hg(II) and Cu(I) ions give complexes where TATZ coordinates solely through thionamide sulfur. It acts as bidentate chelate coordinating through both thiazole nitrogen and thionamide sulfur in complexes of Fe(II), Ni(II) and Cu(II), yielding high spin octahedral complexes. The donor properties of TATZ are compared with some related N-substituted thioamides. ACDTC and its N- and S-substituted derivatives with different metal ions have been synthesized. With ACDTC and its S-methyl ester (MeACDTC), complexes of Zn(II), Cd(II) and Hg(II) halides are prepared and characterized by proton and carbon-13 NMR, infrared and electronic spectroscopy. The data suggest bidentate coordination of the ligands as chelates through the –CS? moiety. The complexes of iron(II,III) with ACDTC are also synthesized and are characterized in addition by magnetic susceptibility and Mössbauer spectroscopy. These complexes are of high spin octahedral variety. The coordination in these complexes also occurs via the dithio moiety. Ferrous and ferric complexes of 2-N-(n-butylamino)cyclopentene-1-dithiocarboxylic acid (ACDTCBu) and its S-methyl ester (MeACDTCBu) are also isolated. These complexes are investigated by magnetic susceptibilities, electronic, infrared and Mössbauer spectra. The complexes of ACDTCBu are usual high spin type whereas those of the S-methyl ester show low magnetic moments due to antiferromagnetic interactions. Coordination of ACDTCBu and its S-methyl ester as bidentate chelates bonding via the two sulfur atoms is suggested. The synthesis and characterization of the complexes of iron(II,III) halides and iron(III) thiocyanate with 2-formyl and 2-acetyl thiophene thiosemicarbazones are described. The complexes are characterized by elemental analyses, molar conductance, magnetic susceptibility, electronic, infrared and Mössbauer spectroscopic studies. The ligands were found to be bidentate, hydrazinic nitrogen and thiocarbonyl sulfur being the donor sites. The complexes are low spin type excepting the iron(II) complexes of 2-acetylthiophene thiosemicarbazone which are of high spin variety. Complexes of iron(II,III) salts with symmetric N,N?-pyridyl thiourea (DPYTU) are synthesized; compounds of the type Fe(DPYTU)X?·mH?O where X = Cl?, Br?, NO?? and NCS?; n = 2,3 and m = 0–2 are obtained. The complexes are characterized by elemental analysis, electronic, infrared and Mössbauer spectroscopy and magnetic susceptibility studies. The infrared spectra indicate chelation of the ligand via pyridine nitrogen and thiocarbonyl sulfur, the other pyridine nitrogen presumably acts as bridging group, resulting in the formation of polymeric complexes. Magnetic susceptibility and Mössbauer spectroscopic measurements suggest high spin distorted octahedral complexes. The electronic spectral data support this conclusion. Ferrous and ferric complexes of 2,4-dithiobiuret (DTB) of the type Fe(DTB)?X? where m,n = 1–3 and X = Cl?, Br?, I? and SO?²?, and a neutral complex Fe(DTB-H)? are synthesized. The complexes are characterized by elemental analyses, magnetic susceptibility, infrared, electronic and Mössbauer spectroscopic studies. From infrared spectra, DTB was found to act as bidentate chelate coordinating through the two thiocarbonyl sulfur; metal-sulfur vibrations have been assigned. The magnetic measurements, electronic and Mössbauer spectra are consistent with low spin octahedral structures for ferric complexes and high spin octahedral geometries for ferrous complexes. The donor properties of DTB are compared with related molecules like biuret, monothiobiuret and guanyl thiourea.