Complexes hétérobimétalliques à ligand assembleur oxo ou thiooxo d'éléments s, d et f. : Influence des ligands oxalate et squarate sur la structure : Etude de tels complexes comme précurseurs de céramiques

Abstract

The following heterbimetallic complexes were prepared and structurally characterized by single crystal X-ray diffraction : [Ba(H₂O)₅][Cu(C₂O₄)₂(H₂O)]1, [Ba(H₂O)₂]₂[Cu(H₂O)₂](C₄O₄)₃ 2, [Gd(H₂O)₄]₂[Cu(H₂O)₄](C₄O₄)₄], 2H₂O 3, and [Cu₀.₉Mn₀.₁(H₂O)₄](C₄O₄) 4. 1 contains columnar arrangements of anionic [Cu(H₂O)(C₂O₄)₂]²⁻ units. 2 is made of cationic layers [{Ba(H₂O)₂(C₄O₄)²⁺]₂∞ with bischelating, tetrakis monodentate squarate ligands; the layers are linked by intervening [Cu(H₂O)₂](C₄O₄)²⁻ anionic units. 3 is made of heterobimetallic neutral layers {[mu₃₋C₄O₄]Gd(H₂O)₄}₂(mu₂₋C₄O₄)₂[Cu(H₂O)₄]}₂∞. 4 is made of unlimited neutral chains ...[M(H₂O)₄]-(C₄O₄)-[M(H₂O)₄]-(C₄O₄)⁻... where the cations Cu²⁺ an Mn²⁺ are statistically distributed. E fifth, homometallic, chain compound, [Cu(H₂O)₄]₄(NC₅H₅)₂(C₄O₄) 5, was obtained incidentally and studied. The variations of the measured magnetic susceptibilities versus the temperature in the 4 K – 300 K range showed only weakest antiferromagnetic couplings in 1, 2 and 5. No significant magnetic interaction was found in 3. In 4, the observed magnetic behaviour suggested a 1-D ferrimagnetic interaction. The thermal behavious were studied by DTA and GTA run in a He:O₂ atmosphere up to circa 900°C. The final decomposition products were: a maxture of BaCO₃, BaCuO₂ and CuO for 1, BaCO₃ and BaCuO₂ for 2,, CuO and MnO for 4, and the bimetallic Gd₂CuO₄ for 3. The second part is a study of the thermal decomposition of the heterobimettalic La-Ni dithio- oxalate, both in an oxygenated atmosphere and under vaccum. In the presence of oxygen, mixed NiO end La₂O₂(SO₄) resulted at 880°C. Under vacuum, crytallized oxosulfide La₂O₂S formed at 700°C.