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Alkoxide complexes of rhenium

precursors of nanomaterials

Nikonova, Olesya A. (2011). Alkoxide complexes of rhenium. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2011:22
ISBN 978-91-576-7557-6
[Doctoral thesis]

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Abstract

The thesis presents the work constituted by two major parts: (1) – synthesis of new mono-, bi- and trimetallic complexes based on Re, Nb and Ta and their physical-chemical characterization, and (2) – preparation of nanostructural functional materials derived from these complexes. The precursors and materials were characterized by FTIR, NMR, MS, SEM–EDS, TEM and X-ray diffraction.

The electrochemical method and the interaction of Re₂O7 with M₂(OR)10 (M = Nb or/and Ta) were used to obtain Re₄O₄(OEt)₁₂ and (M1-xM'x)₄O₂(OR)₁₄(ReO₄)₂ (M = Nb; M' = Ta; R = Me, Et, nPr), where x = 0–1, respectively. The structures of these complexes were determined by single-crystal X-ray diffraction. The influence of the increasing ligand size on the solubility and stability of the complexes Re₄O₄(OEt)₁₂ and (M1-xM'x)₄O₂(OR)₁₄(ReO₄)₂ (M = Nb, M' = Ta; R = Me, Et, nPr) has been established.

Nanosized Re metal particles (approximately 3 nm in diameter) were obtained from Re₄O₄(OEt)₁₂ by thermal decomposition in inert atmosphere at as low temperature as 380°C. Semi-ordered macro porous monoliths with the pore size in the range 100–250 nm, with the crystal structure related to the γ-Ta₂O₅, were produced from (Nb1-xTax)₄O₂(OMe)₁₄(ReO₄)₂ (x = 0.3, 0.5, 0.7) via thermal decomposition in air at the temperatures ≤ 1000°C, while in dry nitrogen the α-Nb₂O₅ for the Nb-rich precursors and γ-Ta₂O₅ for Ta:Nb ≥ 1:1 at the temperatures ≤ 1000°C were formed.

The Re₄O₄(OEt)₁₂ and Ta₄O₂(OEt)₁₄(ReO₄)₂ alkoxide complexes have been used as precursors for Re oxide based catalysts. The simultaneous presence of the chemically connected oxidative (perrhenate) and acidic (tantalum oxide) components in the catalyst permit one-step production of DMM.

The hydrolysis of (M1-xM'x)₄O₂(OEt)₁₄(ReO₄)₂ (M = Nb; M' = Ta; x=0–1) leads to formation of nanostaructural materials (nanobeads). The particles remain amorphous and retain Re until rather high temperatures (700°C). The Re content is lost at 1000°C with formation of porous nanobeads with crystal structure related to the γ-Ta₂O₅ and α-Nb₂O₅ for the corresponding precursors.

Authors/Creators:Nikonova, Olesya A.
Title:Alkoxide complexes of rhenium
Subtitle:precursors of nanomaterials
Series/Journal:Acta Universitatis agriculturae Sueciae (1652-6880)
Year of publishing :2011
Volume:2011:22
Number of Pages:80
Papers/manuscripts:
NumberReferences
I.Nikonova O.A., Jansson K., Kessler V. G., Sundberg M., Baranov A.I., Shevelkov A.V., Drobot D.V., Seisenbaeva G. A. (2008). Electrochemical Synthesis, Structural Characterization and Decomposition of Rhenium Oxoethoxide, Re4O4(OEt)12. Ligand Influence on the Structure and Bonding in the High-Valent Tetranuclear Planar Rhenium Alkoxide Clusters. Inorganic Chemistry 47, 1295-1300.
II.Nikonova O.A., Kessler V.G., Seisenbaeva G.A., Drobot D.V., Shcheglov P.A. (2007). Synthesis and X-ray Single Crystal Study of Niobium and Tantalum Oxo-Ethoxo-Perrhenates M4O2(OEt)14(ReO4)2. Polyhedron 26(4), 862-866.
III.Nikonova O.A., Seisenbaeva G.A., Kessler V.G., Shcheglov P.A., Drobot D.V. (2007). Comparative Study of Bimetal Alkoxo Complexes of Rhenium, Niobium and Tantalum by Single-Crystal X-ray Diffraction and IR Spectroscopy. Russian Journal of Inorganic Chemistry 52(11), 1687-1692.
IV.Nikonova O.A., Kessler V.G., Seisenbaeva G.A. (2008). Substitution Features in the Isomorphous Replacement Series for Metal-Organic Compounds (NbxTa1-x)4O2(OMe)14(ReO4)2, x = 0.7, 0.5, 0.3—Single- Source Precursors of Complex Oxides with Organized Porosity. Journal of Solid State Chemistry 181(12), 3294-3302.
V.Nikonova O.A., Capron M., Fang G., Faye J., Mamede A.-S., Jalowiecki-Duhamel L., Dumeignil F., Seisenbaeva G.A. (2011) Novel approach to rhenium oxide catalysts for selective oxidation of methanol to DMM. Journal of Catalysis, accepted, in press.
VI.Nikonova O.A., Kessler V.G., Seisenbaeva G.A. Morphology and crystallinity control of early transition metal complex oxide nanobeads. Manuscript.
Place of Publication:Uppsala
Publisher:Dept. of Chemistry, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-7557-6
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Subjects:Obsolete subject words > NATURAL SCIENCES > Chemistry
Agrovoc terms:catalysts, chemical synthesis, oxides, x rays, microscopy
Keywords:alkoxide, nanomaterials, semi-ordered macro porous materials, catalyst, nanobeads, single-crystal X-ray diffraction, SEM, TEM
URN:NBN:urn:nbn:se:slu:epsilon-e-4
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-4
ID Code:2464
Department:(NL, NJ) > Dept. of Chemistry (until 131231)
Deposited By: Olesya Nikonova
Deposited On:25 Mar 2011 00:00
Metadata Last Modified:02 Dec 2014 10:18

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