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SYNTHESIS OF COMPLEX OXIDES FROM METAL ALKOXIDES

SYNTHESIS OF COMPLEX OXIDES FROM METAL ALKOXIDES [Pg.127]

Therefore, in this book we do not by any means intend to provide a comprehensive treatise on the subject. The aim of this chapter is rather to show a few illustrations of the application ofmetal alkoxides in the synthesis of complex oxides. [Pg.128]

In particular, we have chosen to have a close look at the synthesis and properties of ferroelectrics and related materials, where the sol-gel method with application ofmetal alkoxide precursors seems to have produced the most promising results. In most cases we have selected for discussion in this chapter those works on the preparation of complex oxides, emphasized that the chemistry of the precursors and its role for the properties of complex oxide phases. [Pg.128]

Synthesis of complex oxides from metal alkoxides includes the preparation of the initial solution, hydrolysis, drying, and thermal treatment of the product. Despite the apparent simplicity and versatility of the scheme, the properties of oxides are extremely sensitive to the conditions of their preparation. The commonly used precursor for oxides preparation is a solution of M(OR) in organic solvents. The heterogeneous precursor usually affects the homogeneity of the future oxide phase. [Pg.128]

Therefore, in the course of the studies of bimetallic alkoxides it turned out that one of the most important features for their application in sol-gel films preparation lies in their ability to undergo partial decomposition via hydrolysis, oxidation, or elimination of ethers or esters with formation ofM-O-M bridges (see, e.g., Section 10.1), fragments of future complex oxide phases. Formation of bimetallic oxoalkoxides ensures homogeneity on the atomic scale of the complex oxide formed in the process of the transformation M(OR)n — M2Ob. [Pg.129]


Chapter 10. Synthesis of complex oxides from metal alkoxides... [Pg.129]

The inverse-micelle approach may also offer a generalized scheme for the preparation of monodisperse metal-oxide nanoparticles. The reported materials are ferroelectric oxides and, thus, stray from our emphasis on optically active semiconductor NQDs. Nevertheless, the method demonstrates an intriguing and useful approach the combination of sol-gel techniques with inverse-micelle nanoparticle synthesis (with OTO erafe-temperature nucleation and growth). Monodisperse barium titanate, BaTiOs, nanocrystals, with diameters controlled in the range from 6-12nm, were prepared. In addition, proof-of-principle preparations were successfully conducted for Ti02 and PbTiOs. Single-source alkoxide precmsors are used to ensure proper stoichiometry in the preparation of complex oxides (e.g. bimetallic oxides) and are commercially available for a variety of systems. The... [Pg.5580]

In the preparative section 3.2 devoted to metal-carbene complexes, it is shown how the a-elimination reaction from high oxidation state early-transition-metal-alkyl complexes is one of the general methods of synthesis of Schrock s Ta and Nb alkylidene complexes. The other direction, formation of an alkylidene from an alkylidyne complex, can also be a valuable route to metal alkylidenes. For instance, Schrock s arylamino-tungsten-carbynes can be isomerized to imido-tungsten-carbene by using a catalytic amount of NEts as a base. These compounds are precursors of olefin metathesis catalysts by substitution of the two Cl ligands by bulky alkoxides (dimethoxyethane then decoordinates for steric reasons), and this route was extended to Mo complexes ... [Pg.211]

The reaction requires the use of a catalyst for the alkaline earth metals, rare earth metals and aluminium. The most common approaches are the use of (in the laboratory practice only) the salts of mercury(II) such as HgC or Hg(OAc)2. Very small portions of these salts cause amalgamation of the metal surface (and thus clean it from the oxide layer) and facilitate the reaction with alcohols. The larger scale synthesis (and thus the industrial one—in the scope of pollution danger) uses the initial addition of solid iodine (1 g or less per 1(X) g ofalkoxide to be prepared). Formation of metal iodide serves both for cleaning the surface and increases also slightly the acidity of alcohols via formation of solvate complexes. In the case of barium, the application of dry ammonia gas has been reported for this purpose (Caulton, 1990 Drake, 1992). The major factor facilitating the reaction ofmetals with alcohols is the solubility of the alkoxides formed. Insoluble alkoxides form a protective layer on the surface of the metal and it hinders the reaction. Even the reaction of sodium with BuOH in toluene may be almost stopped by the formation of poorly soluble NaO Bu. [Pg.4]


See other pages where SYNTHESIS OF COMPLEX OXIDES FROM METAL ALKOXIDES is mentioned: [Pg.127]    [Pg.8]    [Pg.140]    [Pg.160]    [Pg.631]    [Pg.597]    [Pg.200]    [Pg.577]    [Pg.281]    [Pg.60]    [Pg.242]    [Pg.351]    [Pg.66]    [Pg.548]    [Pg.251]    [Pg.598]    [Pg.402]    [Pg.156]    [Pg.276]    [Pg.181]    [Pg.1846]    [Pg.255]    [Pg.214]    [Pg.193]    [Pg.136]   


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Alkoxide complex

Alkoxide oxidation

Alkoxides metal complexes

Alkoxides synthesis

Complex metal oxides

Complexes alkoxides

From alkoxides

Metal alkoxide

Metal alkoxide complexes

Metal alkoxides

Metal alkoxides synthesis

Metal complexes, synthesis

Metal oxides, synthesis

Of from oxidation

Oxidation of alkoxide

Oxide-alkoxides

Synthesis of metal complexes

Synthesis of metal oxides

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