New bismuth(III), lanthanum(III), praseodymium(III), and heterodinuclear Bi-La and Bi-Pr complexes with polyaminocarboxylate ligands

New Bi(III), La(III) and Pr(III) complexes with a variety of high-denticity polyaminocarboxylic acids (H(4)edta, H(5)dtpa, H(6)ttha, H(4)Cydta, H(5)hpdta, H(4)egta) have been synthesized and characterized spectroscopically by FTIR. In the case of the decadentate ttha ligand, homodinuclear M-2(ttha) (M = Bi, La, Pr) and heterodinuclear MM'(ttha) complexes were isolated. Detailed investigations of their thermal degradation scheme were carried out in relationship with the possible use of these complexes as molecular precursors for the formation of mixed Bi-La and Bi-Pr oxides in which the crystal structure of the fluorite-like delta-Bi2O3 phase can be stabilized at room temperature. Decomposition proceeds in three successive stages, consisting of dehydration, ligand pyrolysis leading to monoxo-, dioxo- or simple carbonates, depending on the metal nature, and finally decarbonatation producing the corresponding oxide: alpha-Bi2O3, La2O3, Pr6O11, BiLaO3 or BiPrO3. (C) 2002 Elsevier Science (USA).