Mononuclear Transition Metal Cymantrenecarboxylates as Precursors for Spinel-Type Manganites

Novel mononuclear cymantrenecarboxylate complexes of transition metals, [Co(H2O)6](CymCO2)2·4H2O (Cym = (η5-C5H4)Mn(CO)3) (1), [Ni(H2O)6](CymCO2)2·4H2O (2), [Zn(H2O)6](CymCO2)2·4H2O (3), [Co(CymCO2)2(imz)2] (imz = imidazole, 4), [Co(CymCO2)2(bpy)2]·2PhMe (bpy = 2,2′-bipyridyl, 5), [Ni(CymCO2)(bpy)2(H2O)][CymCO2]·0.5MePh·2H2O (6), [Cu(CymCO2)2(imz)2] (7), and [Cu(CymCO2)2(bpy)(H2O)] (8), were obtained and characterized by single-crystal X-ray analysis. Complexes 1–3 are isostructural. Magnetism of the Co complexes 1, 4, and 5 was studied; it was shown that they exhibit the properties of field-induced single-molecule magnets with magnetization reversal barriers (ΔE/kB) of 44, 13, and 10 K, respectively. Thermal decomposition of complexes 1–8 was studied by means of DSC and TGA methods. The final products of thermolysis of 1–6 in air, according to powder XRD data, are the pure spinel phases MMn2O4; for the cases of copper complexes, the mixtures of CuMn2O4 and CuO were found in the products.