Synthesis, spectral and thermal studies of some 3d-metal hydroxybenzoate hydrazinate complexes

Metal o- or p-hydroxybenzoate hydrazinate complexes of the types: Mn(o-C6H4(OH)COO)(2) N(2)H(4)2H(2)O; ML(2)N(2)H(4), where M is Cu(II), L is o-hydroxybenzoate(salicylate) and M is Zn(II), L is o- or p-hydroxybenzoate; ML(2)2N(2)H(4), where M is Co(II) and Ni (II) and L is o- or p-hydroxybenzoate, and bishydrazinium metal salicylates (N2H5)(2)M(o-C6H4 (OH)COO)(4), where M is Co(II) and Ni(II), have been prepared and characterised by magnetic, spectral, thermal and XRD studies. IR spectral data reveal the monodentate coordination of hydroxybenzoates through COO- coordination of N2H5+, bidentate bridging of N2H4 and coordination of H2O in the Mn complex. The magnetic and electronic spectral data indicate octahedral coordination around Mn, Co and Ni and square-planar coordination around Cu ions. The simultaneous TG-DTA data show that Ni and Cu salicylate hydrazinate complexes undergo complete exothermic decomposition, whereas other complexes decompose both by endothermic and exothermic modes to produce metal oxide as the residual product. Most of the complexes form metal hydroxybenzoates as intermediates. Co and Ni intermediates melt before decomposition. The XRD studies show isomorphism among ML(2)2N(2)H(4), ZnL(2)N(2)H(4) and (N2H5)(2)M(o-C6H4(OH)COO)(4) complexes but not between the series.