Coordinate titanate

Table 5.9 lists examples of polymer systems containing other widely used inorganic fillers that are treated with titanates/zirco nates. The principal effects of the coupling agents in relation to the given application are also shown. Modifications of Ti02 with pyrophosphate- and phosphito-coordinate titanates to produce a highly functional metal oxide [53] and an acrylic colorant [54] have been described. Titanates... 

Perovskites have the chemical formula ABO, where A is an 8- to 12-coordinated cation such as an alkaU or alkaline earth, and B is a small, octahedraHy coordinated high valence metal such as Ti, Zr, Nb, or Ta. Glass-ceramics based on perovskite crystals ate characteri2ed by their unusual dielectric and electrooptic properties. Examples include highly crystalline niobate glass-ceramics which exhibit nonlinear optical properties (12), as well as titanate and niobate glass-ceramics with very high dielectric constants (11,14). 

Twelve-membered rings have been obtained using coordination catalysts. The transJmns,ds-cyc. ododec2Lti ien.e has been prepared with a tetrabutyl titanate—diethylalurninum chloride catalyst (48,49) and with a chromium-based system (50). The trans,trans,trans-isom.e-i. has been prepared with a nickel system. 

The less branched, more associated tetraalkyl titanates are more slowly hydroly2ed because titanium is more fully coordinated. The hydrolysis of tetraethyl titanate has also been considered ia terms of its trimeric form ... 

The orange-red titanium acetylacetone chelates are soluble in common solvents. These compounds are coordinately saturated (coordination number equals 6) and thus much more resistant to hydrolysis than the parent alkoxides (coordination number 4). The alkoxy groups are the moieties removed by hydrolysis. The initial product of hydrolysis is beheved to be the bis-hydroxy bis-acetylacetone titanate, (HO)2Ti(acac)2, which oligomerizes to a... 

Alkoxy titanium acylate derivatives coordinated with a phosphite diester (phosphonate diester) can be prepared by reaction of a tetraalkyl titanate and an equal molar amount of a carboxyUc acid, such as methacrylic acid or isostearic acid, and a phosphite or phosphonate diester, such as dibutyl hydrogen phosphite (103). These materials reduce the viscosity of a composite system, improve... 

The 1-alkoxytitatranes can be synthesized by the reaction of equimolar amounts of tetraalkyl titanates and triethanolamine (105). X-ray crystallographic analysis of the soHd isolated from the reaction of one mole of triethanolamine and one mole of TYZOR TPT confirms the stmcture as a centrosymmetric dimer having a Ti isopropoxy nitrilotriethoxy ratio of 1 1 1. The titanium atoms have achieved a coordination number of six via a rather unsymmetrical titanium—oxygen bridge (106). 

These alkoxides are liquids or sublimable solids and, unless the steric effects of the alkyl chain prevent it, apparently attain octahedral coordination of the titanium by polymerization (Fig. 21.6). The lower alkoxides are especially sensitive to moisture, hydrolysing to the dioxide. Application of these organic titanates (as they are frequently described) can therefore give a... 

The data obtained while studying the role of aluminumorganic compounds during polymerization by TiCh (157-159) show that an aluminum-organic co-catalyst can be a reversible coordination inhibitor by itself. The decrease in the number of propagation centers by the addition of aluminumorganic compounds to titanium dichloride seems to be caused by the reversible adsorption of the aluminumorganic compound on the titan-... 

The spectrum of the tetrahedrally coordinated tetraphenyl titanate does not resemble the type IV spectrum, primarily due to enlargement of the 20 ev. absorption peak. The second tetrahedral coordination sphere in this compound, consisting of carbon atoms, may account for this change. An analogous change, also attributed to the second coordination sphere, is observed for the octahedral hexacyanides as compared to the other octahedral compounds. 

The coordination most nearly resembles tetraphenyl titanate, of all reference compounds studied this implies tetrahedral coordination. 

Titanates, Zirconates and Hafnates. Li4Ti04 (45) and Ba2Ti04 (46) are titanates for which the tetrahedral coordination of titanium IV with oxygen has been determined by X-ray analysis. The infrared spectrum of the latter com-... 

Generally, nomenclature systems use a base on which the name is constructed. This base can be derived from a parent compound name such as sil (from silane) in substitutive nomenclature (mainly used for organic compounds) or titan a central atom name such as cobalt in additive nomenclature (mainly used in coordination chemistry). 

For a reaction step in which the products are less stable titan the reactants (endergic), the transition state will lie farther along the reaction coordinate toward tile products and the activated complex will have a structure more similar to the products titan the reactants (Figure 5.10). 

If we consider reaction of mesylate ion with methyl bromide, we find that this is an endergic reaction thus the transition state lies along the reaction coordinate farther toward the products titan the reactants (Figure 5.11). The activated complex will therefore have a structure more resembling the products. There will be significant carbon-oxygen bond formation between the mesylate group and carbon and only a weak residual bond between carbon and bromine. The bromine... 

The book explores various examples of these important materials, including perovskites, zeolites, mesoporous molecular sieves, silica, alumina, active carbons, carbon nanotubes, titanium dioxide, magnesium oxide, clays, pillared clays, hydrotalcites, alkali metal titanates, titanium silicates, polymers, and coordination polymers. It shows how the materials are used in adsorption, ion conduction, ion exchange, gas separation, membrane reactors, catalysts, catalysts supports, sensors, pollution abatement, detergency, animal nourishment, agriculture, and sustainable energy applications. 

Compared with 49, 2,5-dioxabicyclo[2.2.2]octan-3-one (54) prepared from sodium 3,4-dihydro-2//-pyran-2-carboxylate has a much low polymerization reactivity [54] Lewis acids such as antimony pentachloride, phosphorus pentafluoride, and boron trifluoride etherate were not effective at all to initiate the polymerization of 54. Trifluoromethanesulfonic acid induced the polymerization of 54, but the yield and molecular weight of the polymer were low. Bicyclic lactone 54 was allowed to polymerize with anionic and coordination initiators such as butyl-lithium, lithiumbenzophenone ketyl, and tetraisopropyl titanate. However, the... 

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