New binuclear ferrocenecarboxylates of rare-earth metals as precursors for ferrites: Syntheses, structures, and solid-phase thermolysis

New ferrocenecarboxylates of rare-earth metals, [Ln2(μ-O,η2-OOCFc)2(μ2-O,O′-OOCFc)2(η2-NO3)2(DMSO)4] (Ln = Gd (I), Tb (II), and Y (III)) and [Gd2(μ-O,η2-OOCFc)2(η2-OOCFc)4(DMSO)2(H2O)2] · 2DMSO · 2CH2Cl2 (IV), are synthesized and characterized by X-ray diffraction analysis. Unlike all earlier known ferrocenecarboxylates of rare-earth metals, in isostructural compounds I–III the Ln atoms are linked by four bridging carboxyl residues, two of which are chelate-bridging (the coordination number of Ln is 9). Binuclear structure IV is formed by two chelate-bridging carboxylate ligands (the coordination number of Gd is 9). Weak antiferromagnetic and weak ferromagnetic interactions between the Gd atoms are observed in complexes I and IV, respectively. The thermal decomposition of the synthesized compounds is studied by differential scanning calorimetry and thermogravimetry. According to the X-ray diffraction data, the final thermolysis products of the complexes in air are garnets Ln3Fe5O12.