Lithium substitution

Bands, which do shift upon lithium substitution, were found in both compounds below 600 cm . The two absorption bands observed near 500 cm in methyllithium appeared at much higher wavenumbers in the corresponding Li compound. Most of the shifts observed upon Li substitution (Table 1) are smaller than the characteristic shifts for harmonic C—Li bonds (about 26 cm for bands near 500 cm ) , as expected since they represent complex vibrational modes. Furthermore, aU of these signals are significantly shifted upon deuterium substitution, which indicates that they involve the motion of hydrogen as well as lithium (Table 1) . ... 

Electrophiles can also be introduced into position 2 of the dihydropyridine cycle. The procedure for obtaining compounds 393 involves preliminary retaliation of substrate 391 with tert-butyl lithium and the subsequent reaction of lithium-substituted heterocycle 392 with the appropriate electrophile [325] (Scheme 3.103). 

Perfluoroalkenylsilver compounds55 have been synthesized by the treatment of perfluoroalkynes,69 perfluoroallenes,70 and 1-trimethylsilyl perfluoroalkenes40 with silver fluoride via the metathesis of lithium-substituted perfluoroalkenes with silver trifluoroacetate 71 and by exchange between perfluorophenyl- or perfluoroisopro-pylsilver and the corresponding iodoperfluoroalkene (Scheme 1.27).49... 

FIGURE 9.2 Neutron-scattering-density profiles p(z) for a lithium-substituted vermiculite. Oxygen plus clay layer is the solid line, hydrogen is the dashed line, and lithium is the stars. The molecular model above shows two sections of clay surface and an undistorted octahedral Li+(H20)6 complex. In this model all six water molecules are hydrogen bonded directly to the clay plate in practice we find that, on average, two of the six water molecules are less strongly oriented toward the plate. 

But it was not to be. Try as we might, the difference in scattering lengths between the 6Li and 7Li isotopes was too small to permit us to measure the lithium ion distribution in the swollen state. We had to content ourselves with the results for the crystalline phase, where the behavior of the lithium ions is different from that of the larger alkali metal cations [27], Potassium and cesium ions bind directly to vermiculite clay surfaces rather than hydrating fully. Because only lithium-substituted vermiculites of the alkali metal series will swell macroscopically when soaked in water, it seems that interlayer cations must form fully hydrated ion-water complexes if the particles are to expand colloidally. This conclusion has since been supported... 

Lithium substitution of H atoms in Bu N=CH—CH=NBu to give (9-XXXI) allows the synthesis of [(dab)Li] complexes of lanthanides173 by reaction with the trichlorides LnX3(THF)3. 

The Unusual Structures, Energies, and Bonding of Lithium-Substituted Allenes, Propynes, and Cyclopropenes. A. J. Kos, T. Clark, and P. v. R. Schleyer, Angeiv. Chem., 96, 622, (1984). Die ah Initio Berechnung der Struktur von 1,3-Dilithloaceton. 

There are a number of indirect, yet valuable, methods for the preparation of imine anions. The more important of these provide convenient access to regiochemically defined anions, especially those that would otherwise be derived by deprotonation at the more substituted a-carbon. For example, Wender reported that reduction of imines derived from a,P-unsaturated ketones leads to lithium substituted anions, in analogy to the reduction of the ketones themselves (equation 43). ... 

A major limitation of the Lagow procedure for preparative purposes is the trapping of the lithiocarbon species in the lithium metal matrix, but techniques have been developed to minimize this problem The reaction products have been purified by grinding under argon and the resulting powder sieved resulting in removal of substantial amounts of lithium metal and approximately 85 % pure lithiocarbon product. Subsequently the products were extracted with cold THF to remove LiCl and were then separated from lower density lithium rich particles by flotation on cold THF. Unfortunately, however, methods have not yet been developed to separate one lithium substituted hydrocarbon from a mixture of others. 

Of the wide range of catalyst materials studied, lithium-substituted nickel oxides are unusual in that they form sufficiently simple structures that a relatively complete characterization is possible. In addition, the origin of the selectivity imparted in nickel oxide by lithium substitution is particularly interesting. NiO readily reacts with CH4 at temperatures above 873 K, but only CO2 and H2O are formed.i2>2 This is quite different than the case of MgO, which has little or no reactivity toward methane without the addition of alkali metal. Somehow, substitution of Li cations for Ni cations converts nickel oxide from a material which is highly active and selective for complete combustion to one that can be highly selective for hydrocarbon production. 

A polymer complex containing Ru(bpy)3 " pendent groups was obtained by the reaction of a lithium-substituted polystyrene with 2,2 -bip)nidyl followed by interaction with cw-Ru(bpy)2 [83]. Another example is binding of 4,4 -dicarboxy-2,2 -bipyridyl to a copolymer of / -aminostyrene followed by reaction... 

The incorporation of alkali metals in the perovskite La1 jeMjeAlo.7Nio.3O3 (M = Li, Na, K) allowed to increase the catalytic performances particularly with sodium substitution x = 0.25), while the lowest amount of coke formation was found for lithium-substituted materials (x = 0.2), proving that basic promoters improved the stability of nickel-based catalysts [41],... 

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