New bis-hydrazine lanthanide complexes with 3-acetoxybenzoic acid (3-abH) of formula, [Ln(3-ab)3(N2H4)2]·xH2O where Ln = La, Ce, Pr and Gd andx=0; Ln = Nd and Sm andx=1,and monohydrazine complexes of some trivalent lanthanides with 4-acetoxybenzoic acid (4-abH) of formula, [Ln(4-ab)3(N2H4)]·H2O where Ln = La, Ce, Pr, Nd, Sm and Gd have been prepared in ethanolic medium and characterized by spectroscopic techniques (IR and UV reflectance), microelemental analysis, thermoanalytical technique, powder XRD, SEM-EDS studies, and magnetic susceptibility measurements. The IR spectra of both series show bidental coordination of carboxylate ion with the metal by displaying,νC=O (asym)in the range of 1587–1602 cm−1and theνC=O (sym)in the range of 1433–1410 cm−1, with a separation of around 200 cm−1. The ester C = O remains unaltered indicating the noninvolvement in coordination. All the complexes showνN-Nabsorption in the range of 929–962 cm−1indicating the presence of hydrazine in a bridged bidentate fashion. The thermal data reveals that the hydrated compounds show endothermic dehydration followed by exothermic decomposition to leave their metal oxide as end products, and the anhydrous compounds undergo exothermic decomposition to form the respective metal oxide residues.
Hydrazine is the simplest diamine containing two lone pair of electrons. It forms variety of compounds with more number of carboxylic acids, such as simple aliphatic mono and di carboxylic acids 1,2 aromatic mono and di carboxylic acids 3,4 tri and tetra carboxylic acids 5,6 , which have been reported in the literature. Many bis-hydrazine and hydrazinium metal carboxylates are used as precursors for metal oxides and mixed metal oxides 7-15. Though studies have been done on 4-acetamido benzoate synthesis of lanthanide coordination polymers using 4-acetamido benzoic acid and various modes of coordination of 4-acetamido benzoate (monodentate, chelating and multidentate bridging nature) 16-20 , a detailed study of transition metal complexes of isomeric acetamido benzoic acids in the presence of hydrazine has not been attempted so far. In this paper, we report the synthesis, spectral and thermal studies of some transition metal complexes of 2-acetamido, 3-acetamido and 4-acetamido benzoates with hydrazine. The
ABSTRACT. New hydrazine complexes of some divalent transition metal ions of formulae, [M{(2-ab)2(N2H4)}].3H2O, [M{(3-ab)2(N2H4)}].3H2O and [M{(4-ab)2(N2H4)2}].2H2O where M = Co, Ni, Zn and Cd; 2-abH = 2-acetoxy benzoic acid, 3-abH = 3-acetoxy benzoic acid and 4-abH = 4-acetoxy benzoic acid were prepared using their respective metal nitrates and hydrazine hydrate at pH 6 and 5, respectively, and characterized by elemental analysis, IR and UV-reflectance spectroscopic techniques, thermo analytical technique, powder XRD, SEM-EDX and magnetic susceptibility measurements. All the transition metal complexes were sparingly soluble in water. The IR spectra of complexes showed N-N absorptions of hydrazine in the range of 964-988 cm-1 substantiating the bidentate bridging coordination of hydrazine. They showed endothermic decomposition in the range of 67-100 °C, exothermic dehydrazination in the range, 210-281 °C and an oxidative decomposition between 350 and 490 °C to form their respective metal oxides. The electronic spectral and magnetic susceptibility data could substantiate the distorted octahedral geometry of nickel and cobalt complexes and the XRD pattern indicates the existence of isomorphism. Crystals of [Cd(H2O)3((C6H4(4-OH)(COO))2].H2O obtained as by-product, was also characterized using single crystal XRD, IR and thermal studies.
KEY WORDS: Acetoxy benzoic acids, Hydrazine, Thermal analysis, Single crystal XRD
Bull. Chem. Soc. Ethiop. 2021, 35(2), 337-350.
DOI: https://dx.doi.org/10.4314/bcse.v35i2.9
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