Cesium atoms reactions with

Gomplexation of cesium at a tetracarbaborane cage was achieved in the reaction of [ / >-2,4,6,12-(SiMe3)4-2,4,6,12-C4B8H8] with an excess quantity of cesium metal in THF. In the polymeric structure of the cesium salt, one cesium atom occupies an apical position above an open six-membered C3B3 face 5.19... 

Before proceeding with the next topic, we should like to emphasize again the significance of this work on the problem of understanding catalysis. The conversion of a cesium atom to a cesium ion is the simplest illustration of a catalytic reaction since it involves the transfer of an electron. To convert about 10% of the cesium atoms in free space into cesium ions would require a temperature of 20,000°K. This can be calculated from the equations... 

Simple 2,2-dibutyl-l,3,2-dioxastannolanes form solid complexes of monomer units with certain nucleophiles, such as pyridine and dimethyl sulfoxide, that have 1 1 stoichiometry and pentacoordinate tin atoms.62 Such complexes are less stable for more-substituted stannylene acetals, such as those derived from carbohydrates.62 Unfortunately, the precise structures of these complexes have not yet been defined. Addition of nucleophiles to solutions of stannylene acetals in nonpolar solvents has been found to markedly increase the rates of reaction with electrophiles,63 and transient complexes of this type are likely intermediates. Similar rate enhancements were observed in reactions of tributylstannyl ethers.57 Tetrabu-tylammonium iodide was the nucleophile used first,57 but a wide variety of nucleophiles has been used subsequently tetraalkylammonium halides, jV-methylimidazole,18 and cesium fluoride64,65 have been used the most. Such nucleophilic solvents as N,N-dimethylformamide and ethers probably also act as added nucleophiles. As well as increasing the rates of reaction, in certain cases the added nucleophiles reverse the regioselectivity from that observed in nonpolar solvents.18,19... 

If empty zeolite LTA is exposed to cesium gas, and redox reaction with the exchangeable cations of the zeolite can occur, then the product Cs" " ions may seal the zeolite crystals. Everything within the zeolite may be encapsulated, including the product atoms, perhaps as neutral clusters. Well, nearly all cations, including Na" ", are reduced by Cs(g) only some of the other alkali-metal cations may resist reaction. Depending upon the mobility of the Cs" " ions at the reaction temperature, the surfaces of the crystals may be closed initially. If the reaction proceeds, the entire volume of the zeolite may be sealed. The ultimate outcome of the process will depend upon the mobilities of all the atoms and ions in the structure at the reaction temperature, and upon considerations of the stability and lability of any structural subunits which may form. 

X zeolites exchanged with cesium and impregnated with cesium species were active as catalysts for the Knoevenagel reaction between the aldehyde obtained by the hydro-formylation of limonene and ethyl acetoacetate. The product distribution observed has shown that other reactions were occurring, such as decarboxilation and aldol condensation reactions that also led to products of potential commercial interest. The best results were obtained for the sample with 14 cesium atoms impregnated per unit cell, at 403 K and ethyl acetoacetate / menthene molar ratio of 5. In such a condition, yields of products of interest as intermediates for fine chemicals production were as high as 90% after 4 h of reaction. 

The reaction of Re(CO)5Br with PhCOSH gives the dimeric complex 30, where the thiocarboxyl sulfur atom is coordinated to the two rhenium atoms [99], whereas heating with cesium thiobenzoate in ethanol leads to the anion complexes 31 in which the S-thiobenzoato ligands are triply bridged to the two rhenium atoms [213]. In addition, reaction with Cs2(SOC-COS) affords (OC)5Re(SOC-COS)Re(CO)5 [326], the structure of which resembles that of the corresponding manganese complex 28. 

The surface tension of a liquid alkali metal mixture also shows pronounced deviation from the mean value. The surface tension of liquid cesium (74 N m x 10 ), lies much below that for sodium (197 Nm x 10 ), and since surface tension reflects the attraction between atoms in the liquid, the concentration of cesium in the surface of the liquid metal mixture should be much greater than in the bulk of the liquid. Consistent with this, the surface tension of pure sodium falls rapidly upon addition of cesium, and in the range 40-100% cesium the surface tension is near to that for pure cesium. A similar behavior has been observed for sodium-potassium mixtures. Many chemical reactions of the liquid alkali metals and their mixtures involve reaction with gases, and care must then be exercised in relating reaction rates with bulk composition when it is the surface composition that is the relevant factor. 

Cesium forms simple alkyl and aryl compounds that are similar to those of the other alkah metals (6). They are colorless, sohd, amorphous, nonvolatile, and insoluble, except by decomposition, in most solvents except diethylzinc. As a result of exceptional reactivity, cesium aryls should be effective in alkylations wherever other alkaline alkyls or Grignard reagents have failed (see Grignard reactions). Cesium reacts with hydrocarbons in which the activity of a C—H link is increased by attachment to the carbon atom of doubly linked or aromatic radicals. A brown, sohd addition product is formed when cesium reacts with ethylene, and a very reactive dark red powder, triphenylmethylcesium [76-83-5] (C H )2CCs, is formed by the reaction of cesium amalgam and a solution of triphenylmethyl chloride in anhydrous ether. 

An 8000-member library of trisamino- and aminooxy-l,3,5-triazines has been prepared by use of highly effective, microwave-assisted nucleophilic substitution of polypropylene (PP) or cellulose membrane-bound monochlorotriazines. The key step relied on the microwave-promoted substitution of the chlorine atom in monochlorotriazines (Scheme 12.7) [35]. Whereas the conventional procedure required relatively harsh conditions such as 80 °C for 5 h or very long reaction times (4 days), all substitution reactions were found to proceed within 6 min, with both amines and solutions of cesium salts of phenols, and use of microwave irradiation in a domestic oven under atmospheric reaction conditions. The reactions were conducted by applying a SPOT-synthesis technique [36] on 18 x 26 cm cellulose membranes leading to a spatially addressed parallel assembly of the desired triazines after cleavage with TFA vapor. This concept was later also extended to other halogenated heterocycles, such as 2,4,6-trichloropyrimidine, 4,6-dichloro-5-nitropyrimidine, and 2,6,8-trichloro-7-methylpurine, and applied to the synthesis of macrocyclic peptidomimetics [37]. 

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