Benzoate Complexes of Dipositive First Row Transition Metal Ions with Hydrazine

Abstract

Hydrazine metal benzoate complexes of the formula M(C₆H₅COO)₂N₂H₄, where M = Mn and Zn and bis(hydrazine) metal benzoate complexes of the formula M(C₆H₅COO)₂(N₂H₄)₂, where M = Fe, Co, Ni, Zn and Mg, and bis(hydrazinium) nickel benzoate complex have been prepared in aqueous solution by the reaction of hydrazinium benzoate and the corresponding metal nitrate hydrates. The complexes were characterised by chemical analyses, magnetic, spectral, thermal and XRD studies. The magnetic moments and electronic spectra reveal that M(C₆H₅COO)₂N₂H₄ is tetrahedral and the other complexes are octahedral. Infrared spectra show that hydrazine is bidentate bridging, while N₂H₅ ⁺ and carboxylate ions are unidentate. Simultaneous TG-DTA shows that the complexes undergo both exothermic and endothermic decomposition via metal benzoate or oxalate intermediates to form the metal oxide. The benzoate intermediates for the Mn, Co and Mg complexes melt before decomposition, whereas the (N₂H₅)₂Ni(C₆H₅COO)₄ complex itself melts before decomposition. X-ray powder pattern reveals that tetrahedral complexes are isomorphous and except (N₂H₅)₂Ni(C₆H₅COO)₄, the other octahedral complexes are isomorphous.