Cesium derivatives

The compounds MC=CCH3 (M = Na, K) were described earlier.1 The rubidium and cesium derivatives have now been obtained by the reaction of the metals with propyne in liquid ammonia, and their crystal structures studied by X-ray powder diffraction. The compounds are isostructural with those isolated previously, and the c/a ratio in the tetragonal unit cell decreases linearly with the increasing ionic radii of the alkali metals ions.120... 

The ternary systems display a variety of structural chemistry depending on the sizes of the alkaline and lanthanide metals (Scheme 3 Fig. 3 [43, 45-57]). The smaller alkali cations determine the expected coordination structures as found in salt-like compounds, e.g., Na3Y (NH2)6 or KY(NH2)4. Layer structures are observed in alkali metal poor systems like MLa2(NH2)7 while cesium derivatives, apart from the lanthanum compounds, form perowskit-like arrangements as in CsEu(NH2)3 and Cs3Ln2(NH2)9. The mono ammoniates of some Cs-systems are probably metastable. Preparation of analogous ternary systems with Li were unsuccessful in contrast to, e.g., LiAl(NH2)4 [58]. 

In solution, all 2,3,4,5-tetraethylstibolide anions 11b are chemically and magnetically equivalent, whereas in the solid state this is only the case for the rubidium and cesium derivatives and the dimeric TMEDA adduct of sodium 2,3,4,5-tetraethylarsolide 11a (M = Na). Exchange and dissociation reactions lead to a magnetic equivalence on the NMR timescale, which can be expected for mainly ionic compounds (Table 5) <20040M3417>. 

At the moment we are investigating the influence of different donor ligands on the structural features especially of the rubidium and cesium derivatives. Such adducts are prepared by adding the corresponding ligand to a suspension of hypersilyl rubidium 4 or cesium 5 in npentane until a clear solution is obtained. Although, in some cases side-reactions occur, such as deprotonation (diphenylmethane) or reduction (pyrene, bipyridine). In addition to the toluene solvates 4a and Sa already mentioned above, the only two crystalline derivatives isolated so far are the adducts with THF as a typical cr-donor and with biphenyl as a further Ji-donor (Fig. 6 and Fig. 7). 

The reduction may be accompanied by secondary reactions with formation of carbon-carbon bonds (see equation 8). The products with n = 2 contain the acetylenediolate anion [ 202] , the sodium, potassium, rabidium, and cesium derivatives being isotypical the reaction of CO with a potassium melt leads to the product with n = 6, containing the anion of hexahydroxybenzene,... 

During their flame spectrometry experiments on mineral waters in 1860, the German chemists Gustav Kirchhoff and Robert Bunsen determined the existence of cesium from the characteristic two blue lines in the spectrum. Likewise, extracts of the mineral lepidolite exhibited two dark red spectral lines from which the presence of Rb was inferred. Thus, cesium derives from the Latin caesius, meaning heavenly blue, whereas rubidium derives from rubidus, the Latin word used to describe a very dark red color. Bunsen was able to isolate pure Rb but not Cs, later purified by C. Setterberg. 

Fig. 3.2. Electronic, paramagnetic volume susceptibility of liquid cesium (derived from data of Preyland, 1979) as a function of reduced density p/p. Total susceptibility data are corrected for ionic diamagnetism and, for the liquid state, are corrected for conduction electron diamagnetism using theories of I nazawa and Matsudawa (1960) solid line) and Vignale et al. (1988) dot-dash line). Dashed line represents Curie law susceptibility along liquid-vapor coexistence curve, calculated for monovalent, atomic cesium. Note the deviation from Curie law behavior of the vapor for p/p. 2.

Fig. 3.2 Electronic, paramagnetic volume susceptibility of liquid cesium (derived from data of Freyland, 1979) as a function of reduced density p/Pc- 59 Fig. 3.3 Effective mass ratio m = of liquid cesium as a function of...

Cesium derivative of 2-acetylanthracene oxime upon short contact with acetylene (5 min) under mild conditions (80°C) selectively forms 0-vinyl oxime of 2-acetylanthracene (44% yield) [227]. The subsequent 3,3-sigmatropic rearrangement of this 0-vinyl oxime tautomer leads to 2-(2-anthryl)pyrrole in 24% yield (Scheme 1.54). The rearrangement is realized in DMSO in the absence of a base (120°C, 30 min). 

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