Heavy alkali metals

A further significant factor slowing the development of the chemistry of the heavy alkali metal derivatives has been the high reactivity of the complexes, with frequent attack of the ethers used to break up the aggregates in hopes to achieve increased solubility. In fact, ether cleavage is a common observation and manipulations at very low temperatures are often required to overcome this issue.9 Ether cleavage may also be suppressed by the introduction of nitrogen-based donors such as TMEDA and PMDTA. 

Table 2 Crystallographically characterized heavy alkali metal primary amides...

The direct reaction of the metal with the chalcogenol is accessible for the heavy alkali metals, which are more reactive and also for the alkaline earth elements. 

The materials usually used to produce such gradients are salts of heavy alkali metals, caesium chloride being the most frequently used. This salt has a high solubility and its low relative molecular mass permits rapid diffusion enabling the gradient to be formed reasonably quickly. Concentrations of salt up to about 2 g ml-1 can be used and are chosen on the basis of information about the density of the test particles or macromolecules. The technique is used frequently in the separation of viral particles and nucleic acids. 

Crystal structures of solvates in which there are significant interactions between heavy alkali metal atoms and neutral arenes include the toluene solvate (K(C6H5Me)2][Lu CH(SiMe3)2 3 / -Cl] (K-c 300.3-312.8 pm),149 the stannate(II) [K(C6H5Me)3][Sn(CH2tBu)3],150 and [(C6H6)KOSiMe2Ph]4 (K-C 323.3(14)-330.8(6) pm).151... 

Alstrom, P. 1986. Electronic properties of first-stage heavy alkali metal graphite intercalation compounds. Synth. Metals 15 311-322. 

The estimated concentrations for the heavy alkali metal elements Rb and Cs are somewhat uncertain due to their variable content in normal chondrites. Nevertheless, the ratio Rb/Sr = 0.009 derived in this calculation is in accord with the value of 0.005 postulated for the whole Moon by Papanastassiou and Wasserburg123 ... 

In contrast to the other elements of group 13, thallium is considered a soft acid in Pearson s soft/hard acid classification (see Hard Soft Acids and Bases).This makes the element and its derivatives unique, and leads to its potentially most outstanding feature the properties of thallium are a subtle blend of some of the most desirable properties of numerous other metals (e.g. heavy alkali metals, silver, mercury, and lead). Thallium compounds are stable in both oxidation states (-1-1 and -1-3). The trivalent cation is quite a strong oxidation reagent, since it is reduced to T1+ easily (standard redox potential E°(TP+ — Tl" ") = -1.25 V). The ease of this reduction is utilized in certain organic reactions. 

Effects of metal size on the coordination enviromnent are nicely demonstrated in the analogous barium compound, obtained in an effort to circumvent the ether cleavage problem using gentler synthetic methods developed for heavy alkali metals. In this method, barium alkoxides were combined with SiMes substituted diphenylmethane. While the method did lead to desilylation in the desired location, upon concentration of the mother liquors of these compounds. 

EF material free, alkali exchanged zeolites are used as quite mild basic catalysts. Light alkali and alkaline earth metal zeolites, such as Na-X, Na-Y [165], alkali-MOR, Na-A and Ca-A [166], have a mild Lewis acid behavior and do not appear to have strong basic character. The same occurs for Na-silica-alumina [167]. However, heavy alkali metal zeolites such as Cs-Y actually act as base catalysts, or rather as acid-base catalysts, for example for toluene side-chain alkylation. Stronger basic character arises from impregnation of alkali zeolites with alkali salts, later... 

Alkali Metals. Herold et al.55 have prepared a new type of intercalation compound by the action of heavy alkali metals on the ternary KC8H2/3. This latter compound is best considered as a second-stage compound in which alternate gaps between the carbon layers are empty, the other gaps containing a double layer of K atoms, the adjacent carbon layers being a distance... 

G. Auffermann, G. Barrera, D. Colognesi, G. Corradi, A.J. Ramirez-Cuesta M. Zoppi (2004). J. Phys. C Condens. Matter, 16, 5731-5743. Hydrogen dynamics in heavy alkali metal hydrides obtained through inelastic neutron scattering. 

An essentially nonaqueous procedure is described for preparing the racemic and optically active forms of the heavy alkali metal complexes (potassium, rubidium, and cesium) of the cobalt(UI) complexes of cdta, edta, and pdta. The... 

Table 2. Temperatures Preparing For Heavy Alkali Metals-graphite Compounds ...

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