Alkali and Alkaline Earth Derivatives

For sodium and potassium chalcogenolates, donor influence on structural pattern has been explored with a special emphasis in donor hapticity. Thus, crown ether complexation allows the isolation of monomeric species, such as [K(SCPh3)(18-crown-6)Lra] (L=thf, CgH6, hmpa, n = 0.5 L=toluene, n = l),36 [K(SMes )(dibenzo-18-crown-6)(thf)],45 [K(STrip)(dibenzo-18-crown- 

The chemistry of alkaline-earth chacogenolates have been developed from the nineties with the structural characterization of the first magnesium thiolate in 1990,69 magnesium and calcium tellurolates in 1992,70,71 and the first magnesium and strontium selenolates in 1994.72 

Only three beryllium compounds have been structurally characterized, the three-coordinate monomers [Be(SMes )2(thf)]73 and [Be(SMes )(SCgH3-2,6-Mes2)(OEt2)]74 and the four-coordinate [ Be(SPh)2(py)(NH3) 2(18-crown-6)] (7).75 

For the heavier alkaline earth elements the characterized compounds are octahedral monomers, dimers, or separated-ion species. The complexes M(SR)2 (M=Ca, Sr, Ba) have been obtained by aminolysis and proved to be soluble in solvents such as py these compounds decompose rather cleanly to their metal sulfides.86 The monomeric species include [M(EMes )2(thf)4] (M=Ca, Sr, Ba E=S, Se),87 89 [Ca(SC6F5)2(py)4],90 [Ca(SMes )2(18-crown-6)] thf,90 or [Ba(Se-Trip)2(18-crown-6)].87 Only a dimeric barium derivative, [Ba(SeTrip) (py)3(thf)]2, has been described.87 For these elements separated ion-triple species, such as [M(18-crown-6)(hmpa)2][EMes ]2 (M=Ca, Sr, Ba E=S, Se)87,88,91 or contact/separated ion-triple species as [Ba(SMes )(18-crown-6)(hmpa)][SMes ] have been reported.91 

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The entire situation changed when Bednorz and Muller (1986) discovered 30 K superconductivity in a cuprate of the La-Ba-Cu-O system. This broke the apparent 23 K barrier for the T. Since 1986, a variety of cuprates have been synthesized and characterized with the maximum reaching 150K. The cuprates are unusual in many ways and do not seem to follow the BCS model. We shall discuss the cuprates at length later in Chapter 7. Alkali and alkaline-earth derivatives of Cgo (buckminsterful-lerene) exhibit superconductivity with a maximum of 35 K. We shall examine these... 

Although it is usual to represent the alkali and alkaline-earth derivatives as MOC(= CRR )R, i.e. as they were mononuclear metal enolates (3), they are actually dinuclear, tetranuclear or hexanuclear aggregates in the solid state and in solution through bridging... 

Alkali and alkaline-earth derivatives of phenol and the lower alcohols (methoxides, ethoxides) have been known for more than a century. Traditional applications for them include use as lubricants (e.g., lithium greases), polymerization catalysts, and surfactant stabilizers. Based on their solubility and volatility (both generally low), alkaline-earth alkoxides were presumed to be... 

Although the ion pairs of a-substituted benzyl anions and the corresponding cations are chiral species, which, in addition, often bear a pyramidal and hence stereogenic carbon atom, in most cases rapid racemization of the alkali and alkaline earth metal derivatives occurs in solution... 

PTFE, FEP and PFA are attacked only by alkaline metals and their organic derivatives elemental fluorine and chlorine trifluoride alkali and alkaline earth metals with their oxides and carbonates above 350°C. The other halogens, aqua regia, nitrosulfuric acid mixtures, oleum (fuming sulfuric acid) and solvents are without significant effects. 

Approximately 25 years after Mond and co-workers had prepared the first carbonyl of cobalt, Co2(CO)8 (78), Hieber obtained HCo(CO)4 by the acidification of salts containing [Co(CO)4] (79), one of the first established carbonylmetallates (80). In 1941, Behrens, a student of Hieber, initiated his important and extensive investigations on the reduction of metal carbonyls and their derivatives by alkali and alkaline earth metals in liquid ammonia (81). At this time he established that various salts of [Co(CO)4]-, including Na[Co(CO)4] and K[Co(CO)4], could be obtained from the neutralization of HCo(CO)4 or the reduction of Cd[Co(CO)4]2 by sodium or potassium in liquid ammonia (4). On the basis of Behrens pioneering studies, we were... 

Stereo specific generation and reactions of allylic alkali and alkaline earth metals have been reviewed121 and solvent-mediated allylation of carbonyl compounds with allylstannanes has been explored.122 Chiral phosphoramides derived from (5 )-proliiie have been used to catalyse asymmetric allylation of aromatic aldehydes by allylic trichlorosilanes.123... 

Wood, D.J., Tranter, T.J., Todd, T.A. 1995. Effect of the interference of alkali and alkaline earth metal ions on the extraction of 90Sr from acidic nuclear waste solutions by 18-crown-6 derivatives in 1-octanol. Solvent Extr. Ion Exch. 13 (5) 829-844. 

Spironaphthoxazine with a crown ether, 8, also shows photochromic behavior that is sensitive to the type of alkali and alkaline earth metal ions [14]. Other derivatives of spiropyran and spiro oxazine, 9-12, which can chelate metal ions were synthesized, and the effects of complexation on their photochromic behavior have been investigated [15-17]. 

It should not be supposed that all metal derivatives of cyclopentadiehe are sandwichlike molecules. In many cases, the metal is joined to just one of the carbons in the ring through a single (cr) bond, which, however, often has considerable ionic character. Metal-to-earbon bonds almost certainly exist in the cyclopentadiene derivatives of the alkali and alkaline-earth metals, the rare earths, and certain of the post-transitioii elements. 

Bis(crown ethers) connected by a flexible spacer are a source of intramolecular sandwich-type complexes with alkali metal ions <1992MI1>. A conformational analysis (based on a combination of semiempirical and ab initio methods) performed on 12-crown-3 38 and 12-crown-4 39 predicted that, in the case of sandwich-type complexation, the nucleophilic cavity of 12-crown-3 rather than that of 12-crown-4 is more prone to complexation with the Na+ ion. Accordingly, ion-selective electrodes based on bis(12-crown-3) derivatives with dialkylmalonate spacers displayed the highest selectivity for Na+ ions among the alkali and alkaline earths investigated, and superior to the Na+ selectivity reached with the bis( 12-crown-4) analogue <2003ANA(480)291>. 

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