Synthesis and characterization of homo- and heterobimetallic niobium(v) and tantalum(v) peroxo-polyaminocarboxylato complexes and their use as single or multiple molecular precursors for Nb-Ta mixed oxides

摘要

New water-soluble bimetallic peroxo complexes of niobium(V) and/or tantalum(V) with high-denticity polyaminocarboxylate ligands have been prepared, characterized from the spectroscopic point of view, and used Lis molecular precursors for Nb-Ta mixed oxides. Four new homobimetallic complexes, (gu)(3)[Nb-2(O-2)(4)(dtpaO(3))]center dot 3H(2)O 1, (gu)(3)[Ta-2(O-2)(4)(dtpaO(3))]center dot 5H(2)O 2, (gu)(3)[Nb-2(O-2)(4) (HtthaO(4))]center dot 2H(2)O 4 and (gu)(3)[Ta-2(O-2)(4)(HtthaO(4))]center dot 3H(2)O 5 and the corresponding heterometallic complexes, (gu)(3)[NbTa(O-2)(4) (dtpaO(3))]center dot 2.5H(2)O 3 and (gu)(3)[NbTa(O-2)(4)(HtthaO4())]center dot 2H(2)O 6 have been obtained. In these compounds, the in situ oxidation of the nitrogen atoms of the PAC ligands into N-oxide groups has been evidenced by IR spectroscopy and mass spectrometry. The thermal treatment of the homonuclear complexes in air at 700 or 800 degrees C, depending on the Ta content, provided Nb2O5 or Ta2O5 while the heteronuclear Compounds led to the solid solution TaNbO5. BET and SEM measurements have been carried out and comparison of the morphology of the samples prepared from homo- and heterometallic precursors is discussed. (c) 2005 Elsevier Inc. All rights reserved.