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  • Author or Editor: B. Sivasankar x
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Abstract  

Cobalt, nickel and zinc dicarboxylate complexes containing neutral hydrazine as bridged bidentate ligand of the type MX(N2H4)n where n=1 for X=OOCCH2COO and n=2 for X=OOCCH2COO, OOCCH2CH2COO and OOCC(CH2)CH2COO have been prepared by aqueous reactions. These complexes have been characterized by analytical, spectral and thermal studies. The electronic spectra coupled with magnetic moments of cobalt and nickel complexes suggest these complexes are of high-spin variety with octahedral geometry. Infrared spectra indicate the bridging bidentate nature of hydrazine moieties present in both mono-hydrazine and bis-hydrazine complexes and the dicarboxylate ions coordinate to the metal as bidentate ligand through the monodentate coordination of each carboxylate ion. However, in the mono-hydrazine metal malonates both carboxylate ions act as bridged ligands. Simultaneous TG-DTA curves of all the complexes in air resulted in the formation of respective metal oxide as final residue at low temperatures (300–400C). These complexes decompose either in single step or decompose through respective metal carboxylate intermediates. In most of the cases the decompositions are exothermic while in some cases they are violently exothermic. The thermal degradation of these complexes in nitrogen atmosphere also gives the respective metal oxide as the final residue.

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Abstract  

Some new and bis-hydrazine lanthanide glyoxylates Ln[OOC-CHO]3(N2H4)2 where Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb or Dy have been prepared and the compositions of the complexes have been determined by chemical analysis and elemental analysis. The magnetic moment and electronic spectra suggest except Ln3+ which is diamagnetic and all the other complexes are paramagnetic. Infrared spectral data indicate the bidentate coordination of carboxylates group is coordinate to lanthanide ion in a monodentate fashion. However, as a whole, glyoxylate ion acts as a bidentate ligand. The curves of all the complexes show multi-step degradation and the final products are found to be the respective metal oxides. The final residues were identified by their metal analysis, infrared spectra and the X-ray powder diffraction patterns. X-ray powder patterns of the complexes are almost super-imposable as expected which is in favour of isomorphism among the series.

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Abstract  

Some bis-hydrazine metal pyruvates of transition metal ions of the formula M[CH3COCOO]2 [N2H4]2, where M = Co, Ni, Zn or Cd, tris-hydrazine metal pyruvates of the formula M[CH3COCOO]2 [N2H4]3, where M = Co, Ni, Zn or Cd, and hydrazinium metal pyruvates [N2H5]2M[CH3COCOO]4, where M = Co or Ni have been prepared and the compositions of the complexes have been determined by chemical analysis. The magnetic moments and electronic spectra of the complexes suggest a high-spin octahedral geometry for them. Infrared spectral data of bis-hydrazine complexes indicate the bidentate bridging mode shown by hydrazine molecules and mono dentate coordination by pyruvate ions. However, in tris-hydrazine complexes the pyruvate ions are ionic in nature. In hydrazinium complexes two hydrazinium ions and four pyruvate ions show unidentate coordination mode resulting in six coordination around metal ions. Thermo gravimetry and differential thermal analysis in air reveal that most of the complexes decompose in one step to give the respective metal carbonate as the final residue. However, the hydrazinium complexes yield Co2O3 or NiO as the residue. The final residues were identified by their X-ray powder data. The X-ray powder diffraction patterns of each series of complexes reveal isomorphism among the series.

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Abstract  

Hydrazinium metal ethylenediaminetetraacetate complexes of molecular formula (N2H5)2[Mg(edta)·H2O], (N2H5)3[Mn(edta)··H2O](NO3)·H2O, N2H5[Fe(edta)·H2O], N2H5[Cu(Hedta)·H2O] and N2H5[Cd(Hedta)·H2O]·H2O have been synthesized and characterized by elemental and chemical analysis, conductivity and magnetic measurements and spectroscopic techniques. The thermal behaviour of these complexes has been studied by thermogravimetry and differential thermal analysis. The data set provided by the simultaneous TG-DTA curves of the complexes shows the occurrence of three or four consecutive steps such as dehydration, ligand pyrolysis and formation of metal oxides. X-ray powder diffraction patterns of copper and cadmium complexes show that they are not isomorphous. These studies suggest seven coordination for Mg,Mn, Fe complexes and six coordination for Cu and Cd derivatives.

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Abstract  

Some new hydrazinium lanthanide sulphite hydrates of the formula N2H5Ln(SO3)2(H2O)2 where Ln=La, Pr, Nd and Sm and N2H5Ce(SO3)2 have been prepared and characterized by chemical analyses, magnetic studies and electronic and infrared spectroscopy. Thermal degradation of these complexes has been investigated by simultaneous TG-DTA techniques. These complexes decompose in air after dehydration to give the respective lanthanide sulphate as the final residue. However, cerium complex gives a mixture of cerium sulphate and ceric oxide as the end products. Cerium and neodymium complexes have also been subjected to thermal degradation in nitrogen atmosphere and the dehydration of neodymium complex was observed at a higher temperature than in air. The anhydrous neodymium and cerium complexes decompose in one step to give the respective sulphate in nitrogen atmosphere.

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The hydrazinium(1+) metal acetates and malonate dihydrates of the molecular formula [(N2H5)2M(CH3COO)4] and (N2H5)2[M(OOCCH2COO)2(H2O)2] respectively, whereM=Co, Ni or Zn, have been prepared and characterized by chemical analyses, conductance, magnetic, spectral, thermal and X-ray powder diffraction studies. The magnetic moments and electronic spectra indicate that these complexes are of high-spin octahedral variety. The infrared spectra show that the hydrazinium ions are coordinated in the case of acetate complexes, whereas in the malonate complexes the hydrazinium ions are out side the coordination sphere. These complexes undergo exothermic decomposition in the temperature range 150–450°C to give the respective metal oxide as the final residue. The X-ray powder diffraction patterns of the malonate complexes indicate isomorphism among them.

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Hydrazinium metal glycinates [(N2H5 2M(NH2CH2COO)4] and bis(hydrazine)metal glycinates, [M(NH2CH2COO)2(N2H4)2], whereM=Co, Ni or Zn have been prepared and characterized by chemical analyses, magnetic moments and vibrational and electronic spectra. The thermal behaviour of these compounds has been studied by thermogravimetry and differential thermal analyses. These complexes decompose with high exothermicity giving metal powder as the final residue. The X-ray powder data of each set of complexes show isomorphism among themselves.

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Abstract  

Hydrazine hydrate reacts with sulphur dioxide in aqueous solution in the presence of heavier lanthanide(III) ions to give variety of complexes. The nature of product formed is highly pH dependent. Several hydrazine complexes of Ln(III) ions of the compositions Ln(N2H3SOO)3(H2O), Ln2(SO3)3·2N2H4 and N2H5Ln(SO3)2(H2O)2 where Ln = Eu, Gd, Tb or Dy and the precursors for the hydrazinium lanthanide sulphite hydrates, the anhydrous lanthanide hydrazinecarboxylates, Ln(N2H3COO)3 where Ln = Eu, Gd, Tb or Dy have been prepared and characterized by analytical, spectral, thermal and X-ray powder diffraction techniques. The infrared spectral data are in favour of the coordination of hydrazine and water molecules. These complexes decompose in three stages to yield respective oxides as final residue. The final residues were confirmed by their X-ray powder diffraction patterns and TG mass losses. The SEM photographs of some of the oxides show a lot of cracks indicating that large quantity of gases evolved during decomposition.

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Abstract  

Lighter and heavier lanthanide(III) ions react with dihydrazinium salts of ethylenediaminetetraacetic acid (H4edta) in aqueous solution to yield hydrazinium lanthanide ethylenediaminetetraacetate hydrate, N2H5[Ln(edta)(H2O)3]·(H2O)5 where Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy. The numbers of water molecules present inside the coordination sphere have been confirmed by X-ray single crystal studies. The presence of five water molecules as lattice water is clearly shown by the mass loss from the TG analyses. Dehydration of a known amount (1 g) of each sample were carried out at constant temperature (100–110°C) for about 5 min further confirms the number of non-coordinated water molecules. The complexes after the removal of lattice water undergo multi-step decomposition to give respective metal oxide as the final product. The DTA shows endotherms for dehydration and exotherms for the decomposition of the anhydrous complexes. The formation of the metal oxides was confirmed by X-ray powder diffraction studies.

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