Iron(II) carboxylato-hydrazinates: Ferrous fumarato-hydrazinate (FFH), O are being synthesized for the first time. These decompose (autocatalytically) in an ordinary atmosphere to mainly γ γ-Fe 2 O 3 , while the unhydrazinated iron(II) carboxylates in air yield α α-Fe 2 O 3 , but the controlled atmosphere of moisture requires for the oxalates to stabilize the metastable γ γ-Fe 2 O 3 . The hydrazine released during heating reacts with atmospheric oxygen liberating enormous energy, N 2 H 4 + O 2

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... → N 2 + H 2 O; ∆ ∆H 2 O = -621 kJ/mol, which enables to oxidatively decompose the dehydrazinated complex to γ γ-Fe 2 O 3 . The reaction products N 2 + H 2 O 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 γ-Fe 2 O 3 in the ferrite synthesis.