Substitution features in the isomorphous replacement series for metal-organic compounds (Nb{sub x}Ta{sub 1-x}){sub 4}O{sub 2}(OMe){sub 14}(ReO{sub 4}){sub 2}, x=0.7, 0.5, 0.3-Single-source precursors of complex oxides with organized porosity

Journal Article · Mon Dec 15 04:00:00 EST 2008 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2008.09.003· OSTI ID:21212136

Nikonova, Olesya A; Kessler, Vadim G ^[1]

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1. Department of Chemistry, SLU, Box 7015, 75007 Uppsala (Sweden)

Trimetallic oxoalkoxide complexes (Nb{sub 0.7}Ta{sub 0.3}){sub 4}O{sub 2}(OMe){sub 14}(ReO{sub 4}){sub 2} (I), (Nb{sub 0.3}Ta{sub 0.7}){sub 4}O{sub 2}(OMe){sub 14}(ReO{sub 4}){sub 2} (II) and (Nb{sub 0.5}Ta{sub 0.5}){sub 4}O{sub 2}(OMe){sub 14}(ReO{sub 4}){sub 2} (III) were obtained by the interaction of rhenium heptoxide (VII) Re{sub 2}O{sub 7} with niobium and tantalum alkoxides M{sub 2}(OMe){sub 10} (M=Nb, Ta) in toluene. The centrosymmetric molecules (I)-(III) can be considered as a product of condensation of two M{sub 2}(OMe){sub 9}(OReO{sub 3}) molecules with the formation of two oxo-bridges. The specific feature of the structure is the uneven distribution of metal atoms in the crystallographic positions, where one symmetry-independent position, connected via {mu}-O with a perrhenate ReO{sub 4}{sup -} group, is predominantly occupied by niobium atoms, while the other one connected via alkoxide groups has a higher tantalum content. The distribution of Nb and Ta in the structure is truly even only for compound III. The niobium and tantalum content is varied to a different extent for I (less) and for II (more), which is apparently due to small differences in the sizes of these two cations, resulting in preferences for packing of different molecules in the structures. Thermal decomposition of (Nb{sub 1-x}Ta{sub x}){sub 4}O{sub 2}(OMe){sub 14}(ReO{sub 4}){sub 2} (x=0.3, 0.5, 0.7) in air leads to the formation of crystalline species of solid solutions based on tantalum and niobium oxides displaying semi-ordered pores with the size of 100-250 nm. In the dry nitrogen atmosphere, the decomposition leads to the amorphous complex oxides containing rhenium, niobium and tantalum. - Graphical abstract: Thermal decomposition of (Nb{sub 1-x}Ta{sub x}){sub 4}O{sub 2}(OMe){sub 14}(ReO{sub 4}){sub 2} (x=0.3, 0.5, 0.7), single-source complex precursors, in air leads to the formation of crystalline solid solutions based on tantalum and niobium oxides, displaying semi-ordered pores with the size of 100-250 nm. In the dry nitrogen atmosphere, the decomposition leads to the formation of amorphous complex oxides containing rhenium, niobium and tantalum.

• OSTI ID: 21212136
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 12 Vol. 181; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ALKOXIDES
CRYSTALLOGRAPHY
NIOBIUM COMPLEXES
NIOBIUM OXIDES
ORGANOMETALLIC COMPOUNDS
PERRHENATES
PYROLYSIS
RHENIUM OXIDES
SOLID SOLUTIONS
TANTALUM COMPLEXES
TANTALUM OXIDES