Barium alkoxides synthesis

Purex process, 6,940 Barium, pentakis(diacetamide)-stereochemistry, 1, 99 Barium alkoxides synthesis, 2,336 Barium complexes cryptands, 3,53 phthalocyanines, 2, 863 porphyrins, 2,820 pyridine oxide, 3,9 urea, 3,9... 

Bacteriochlorins, 851 Barbituric acid metal complexes, 798 Barium alkoxides synthesis, 336 Barium complexes phthalocyanines, 863 porphyrins, 820 Becium homblei copper accumulation, 964 Benzaldehyde, 2-amino-self-condensation aza macrocycles from, 900 Benzamide, o-mercapto-metal complexes, 655 Benzamide oximes metal complexes, 274 Benzamidine, /V, V -diphenyl-metal complexes. 275 Benzene, 1,2-diamino-reactions with dicarbonyl compounds aza macrocycles from, 902 Benzene, 4 methylthionitroso-metal complexes, 804 Benzenedithiolates metal complexes, 605... 

Poncelet, O., Hubert-Pfalzgraf, L. G., Toupet, L., and Daran, J. C., Molecular precursors of alkaline earths synthesis and structure of [N(C2H40)(C2H40H)2]2Ba, 2EtOH, the first structurally characterized barium alkoxide. Polyhedron, 10, 2045-2050 (1991). 

Bidell W., Shklover V.A., Berke H. Synthesis and structural characterization of new copper complexes and the copper-barium-alkoxide complex BaCu4(0C(R)C(H)C(R)0)4(0R )2(H0R )4 (R = C(CH3)3,R = CH2CH20CH3). Inorg. Chem. 1992 31 5561 Bindal S.R., Kapoor P.N., Mehrotra R.C. Reactions of gallium alkoxides with acyl halides. Inorg. 

Drake S.R., Streib W.E., Chisholm M.H., Caulton K.G. Pacile synthesis and structural principles of the strontium phenoxide Sr4(OPh)g(PhOH)2(THF)6. Inorg. Chem. 1990 29 2707 Drake S.R., Streib W.E., Foiling K., Chisholm M.H., Caulton K.G. Dinuclear barium alkoxides and siloxides displaying variable coordination numbers and asymmetric dispositions ofligands. Inorg. Chem. 1992 31 3205... 

Turowa N.Ya., Popovkin B.A., Nowoselowa A.V. Physicochanical studies of magnesium and alkaline earth alcoholates, Z. Anorg. Allg. Chem. 1969 365 100 Vaartstra B.A., Huffman J.C., Streib W.E., Caulton K.G. Incorporation of barium for the synthesis of heterometalhc alkoxides synthesis and structures of [BaZr2(0-MO-Pr)io]2 and Ba Zr2(O-M0-Pr)9 2- Inorg. Chem. 1991 30 3068... 

Some examples of application of metal alkoxides for synthesis of ferroe-lectrics such as BaTi03-based materials, complex niobates and tantalates, PZT andPLZT-materials, and high-temperature superconductors are discussed below. 10.1. Barium titanate and BaTiOj-based solid solutions... 

Barium titanate and BaTi03-based materials are most commonly used for ceramic capacitors with high dielectric permittivity. BaTi03 powder of extremely high quality (in respect of its purity, stoichiometry, particles morphology) is required for most of the modem applications. This characteristic may be considerably improved by the application of alkoxide precursors. Thus, it is of no surprise that synthesis of BaTi03 and BaTi03-based materials from metal alkoxides attracted considerable attention for several decades. The first works on... 

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... 

The amide method was found to be convenient and straightforward in many cases. An example is the synthesis of soluble barium terr-butoxide, which has a cubane structure (106b). The preparation of this compound by other routes (e.g, direct action of metals with alcohols or chloride-alkoxide interchange), sometimes tends to be complicated due to the incorporation of chloride or oxide moieties within the structural framework of the final alkoxide product. 

Campion, J, F., Payne, D. A., Choe, H. K., Maurin, J. K., and Wilson, S. R., Synthesis of bimetallic barium titanium alkoxides as precursors for electrical ceramics. Molecular structure of the new barium titanium oxide alkoxide Ba4Tii30i2(OC2H40Me)24, Inorg. Chem., 30, 3245 (1991). 

The hydrolysis of a mixture of metal alkoxides forms a fairly successful route for the synthesis of complex oxide powders (67). However, most metal alkoxides are expensive, and their hydrolysis requires carefully controlled conditions because of their sensitivity to moisture. The controlled hydrolysis of a mixture of salt solutions appears to be more difficult, but its use has been demonstrated by Matijevic (61) for a few systems, including barium titanate and strontium ferrite. 

Interest in the synthesis and structural characterisation of less common metalloorganophosphide systems has continued. A range of alkali metal complexes of the phosphide anion (48) has been prepared from the lithio-phosphide by simple metathesis with alkali metal alkoxides. The lithio-phosphide exists as a dimer, but crystallisation of the sodium and potassium drivatives in the presence of TMEDA results in the formation of monomeric species. The caesium triphosphenide (49), involving a phosphorus analogue of the allyl anion, has been prepared from the previously described sodium complex. Unlike the sodium and potassium complexes, which are monomeric, the caesium complex has a polymeric structure. A variety of arylphosphide complexes of magnesium, calcium, strontium and barium have been prepared and their solid state structures characterised. Cop-per(I)-, silver(I)- and gold(I)-complexes of the cyclo-(P ion have also... 

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. 

Among the multiple oxide particles, barium titanate has been successfully prepared from reverse microemulsions (Herrig and Hempelmann, 1996 Beck et al., 1998) by using isopropanolic solution of Ba- and Ti-alkoxides in 1 1 molar ratio, cyclohexane as the oil phase, and various non-ionic surfactants. Such particles were nanometric (less than 20 nm) in size. A series of nanoparticulate aluminates of transition metals Co, Ni and Cu have been synthesized from microemulsions by Meyer et al. (1999). The noteworthy point in this synthesis is the application of heterobimetallic alkoxides as the single source materials of the cations in each case. 

One of the compounds that have drawn attraction of the investigators in the area of sol-gel powderless ceramics is barium titanate, BaTiOs. An initial report came from Frey and Payne (1995) who prepared and used barium and titanium methoxyethoxides under controlled atmosphere for synthesis. The modified alkoxides were hydrolyzed by addition of a solution of water in 2-methoxyethanol. The sol was cast, sealed and aged. Drying at above 50°C yielded monolithic gels sintering of the gels at 800-1300°C produced... 

Frey M.H., Payne D.A. Synthesis and processing of barium titanate ceramics from alkoxide solutions and monolithic gels. Chem. Mater. 1995 7 123-129 Fu X., Qutubuddin S. S)mlhesis of titania-coated sMca nanoparticles using a nonionic water-in-oil microemulsion. Colloids Surf. A 2001 179 65-70 Ganguli D. Sol-emulsion-gel synthesis of ceramic particles. Bull. Mater. Sd. 1999 22 221-226 GanguU D., Chatteijee M. Ceramic Powder Preparation A Handbook. Boston Kluwer Academic Publishers, 1997... 

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