A Study on Thermal Degradation of Hydrazinated Transition Metal Acetamido Benzoates

A study on the preparation of hydrazinated metal complexes of isomeric acetamido benzoic acids with
Co, Ni, Zn and Cd metals and characterization using analytical, FT IR, UV reflectance, micro
elemental analysis, simultaneous TG-DTA, powder XRD, magnetic susceptibility measurements and
SEM-EDX studies have been made and reported here. The complexes have the formulae,
[Ni(2-acamb)2(Hz)].2H2O; [M(2-acamb)2(Hz)].H2O, where M = Co, Cd and Zn; [M(3-acamb)2(Hz)].H2O,
where M = Ni and Co and [M(3-acamb)2(Hz)].2H2O where M = Cd and Zn; [Co(4-acamb)2(Hz)].H2O
and [M(4-acamb)2(Hz)].2H2O where M = Ni, Cd and Zn, 2-acambH = 2-acetamido benzoic acid, 3-
acambH = 3-acetamido benzoic acid , 4-acambH = 4-acetamido benzoic acid and Hz= N2H4. Among
them Ni, Co and Cd complexes of 2-acambH and 4-acambH were obtained at pH 5 and 6
respectively, whereas Zn complexes of both acids were formed at pH 3. 3-acambH complexes were
prepared at pH 5. The IR spectra of the compounds show the N-N stretching frequency absorptions in
the range of 984-926 cm-1, implying the bridging bidentate coordination of hydrazine. The compounds
show ν(C=O) (asym) values in the range 1611-1582 cm-1 and the ν(C=O) (sym) values at 1555-1422
cm-1. The difference of ν(C=O) (asym) and ν(C=O) (sym), which is found to be 48-162 cm-1, indicates
that the carboxylate anion is coordinated to the metal ion in the bidendate fashion. These complexes
eliminate water molecules in the range of 140-177ºC first and then undergo oxidative decomposition
showing exotherms in the range of 200-278ºC and in the range of 400-682ºC to their metal oxides.
Cadmium and zinc complexes indicate their intermediates as carbonates. The electronic spectra and
the magnetic susceptibility values suggest that the coordination number of the complexes is 6 with
distorted octahedral geometry. XRD patterns show isomorphism among the complexes with similar
molecular formulae. The SEM-EDX studies reveal the presence of respective metal oxides.