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Licentiate thesis, 2009

Alkoxide complexes of rhenium, niobium and tantalum

Nikonova, Olesya A.

Abstract

This thesis describes two major methods for preparation of new mono-, bi- and trimetallic complexes on the basis of Rhenium, Niobium and Tantalum: (1) - the electrochemical method for the synthesis of Re4O4(OEt)12 and (2) - the interaction of Rhenium heptoxide, Re2O7, with alkoxo-derivates of Niobium and/or Tantalum, M2(OR)10 for the synthesis of bi- and trimetallic complexes of common formula (M1-xM'x)4O2(OR)14(ReO4)2 (M = Nb; M' = Ta; R = Me, Et), where x = 0–1. The structures of these complexes were determined by single-crystal X-ray diffraction. The products were also characterized by IR, NMR and X-ray powder diffraction. The influence of the increasing ligand size on the solubility and stability of the complexes Re4O4(OEt)12 and M4O2(OR)14(ReO4)2 (M = Nb, Ta; R = Me, Et) has been established. The effect of the ligand and metal ion ratio on the conditions and the chemical composition of the products of thermal treatment have been investigated. Nanosized Rhenium 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 block structures of the L-modification of Ta2O5, were produced from trimetallic complexes of the common formula (Nb1-xTax)4O2(OMe)14(ReO4)2 (x = 0.3, 0.5, 0.7) via thermal decomposition in air at the temperatures ≤ 1000 °C. The thermal decomposition in dry nitrogen atmosphere provides formation of solid solutions, which possess the structures related to the block structure of the H-modification of Nb2O5 for the Niobium-rich precursors and block structure of the L-modification of Ta2O5 for Ta:Nb ≤ 1:1 at the temperatures ≤ 1000 °C.

Keywords

lic.-avh; chemical synthesis; complexing; x rays

Published in


ISBN: 9789186197179
Publisher: Department of Chemistry, Swedish University of Agricultural Sciences

Authors' information

Nikonova, Olesya
Swedish University of Agricultural Sciences, Department of Chemistry

UKÄ Subject classification

Inorganic Chemistry

URI (permanent link to this page)

https://res.slu.se/id/publ/25535