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Carboxylate; hydrazine; metastable oxide; ferrite.

Iron(II) carboxylato–hydrazinates: Ferrous fumarato–hydrazinate (FFH), FeC₄H₂O₄.2N₂H₄; ferrous succinato–hydrazinate (FSH), FeC₄H₄O₄.2N₂H₄;ferrous maleato–hydrazinate (FEH), FeC₄H₂O₄.2N₂H₄;ferrous malato–hydrazinate (FLH), FeC₄H₄O₅.2N₂H₄;ferrous malonato–hydrazinate (FMH), FeC₃H₂O₄.1.5N₂H₄.H₂O; and ferrous tartrato–hydrazinate (FTH), FeC₄H₄O₆.N₂H₄.H₂O are being synthesized for the first time. These decompose (autocatalytically) in an ordinary atmosphere to mainly 𝛾-Fe₂O₃, while the unhydrazinated iron(II) carboxylates in air yield 𝛼-Fe₂O₃, but the controlled atmosphere of moisture requires for the oxalates to stabilize the metastable 𝛾-Fe₂O₃. The hydrazine released during heating reacts with atmospheric oxygen liberating enormous energy, $$N_2H_4 + O_2 \rightarrow N_2 + H_2O;\Delta H_2O = – 621 kJ/mol,$$ which enables to oxidatively decompose the dehydrazinated complex to 𝛾-Fe₂O₃. The reaction products N₂ + H₂O provide the necessary atmosphere of moisture needed for the stabilization of the metastable oxide.

The synthesis, characterization and thermal decomposition (DTA/TG) of the iron(II) carboxylato–hydrazinates are discussed to explain the suitability of 𝛾-Fe₂O₃ in the ferrite synthesis.

K S Rane¹ V M S Verenkar¹

1. Department of Chemistry, Goa University, Goa 403 206, India

Published

February 2001

Manuscript received

3 October 2000