Sodide

A particularly imaginative application of this concept has led to the isolation of compounds which contain monatomic alkali metal anions. For example, Na was reacted with cryptand in the presence of EtNHi to give the first example of a sodide salt of... 

Although crystalline potassides, rubidides and caesides have all been prepared, sodides are more readily isolated since they tend to be the more kinetically and thermodynamically stable. A number of mixed-metal alkalides has also been isolated but they are all of type M+L Na" (n = 1 or 2). 

On page 528 the statement is made that "crystalline [Naclosest packed, large, complex cations with sodide anions in the octahedral holes (Fig. 2-50a). Review the discussion of closest packing in Chapter A and label the atoms in Fig. 12.50 as belonging to layers A and B and indicate the octahedral holes. 

Aside from the effects of ligand stoichiometry and the nature of the solvent, there are also differences in stability of the alkalide ions. The sodide anion is the most stable, and the ceside ion the leash Because of differential stabilities of the alkalide ions and... 

Of particular significance in this respect has been the ability to prepare, characterize and study most intriguing species, the alkalides [2.79, 2.80] and the electrides [2.80, 2.81] containing an alkali metal anion and an electron, respectively, as counterion of the complexed cation. Thus, cryptates are able to stabilize species such as the sodide [Na+ c 9]Na- and the electride [K+ c 9]e-. They have also allowed the isolation of anionic clusters of the heavy post-transition metals, as in ([K+ c cryp-tand]2 Pb52-) [2.82]. 

We saw in Section 6.6 that the reaction of solid sodium with gaseous chlorine to yield solid sodium chloride (Na+Cl-) is favorable by 411 kj/mol. Calculate the energy change for the alternative reaction that yields chlorine sodide (Cl+Na ), and then explain why sodium chloride formation is preferred. 

Draw a Born-Haber cycle for the reaction of sodium with chlorine to yield chlorine sodide (Problem 6.101). 

Since X-ray crystallography cannot observe the lone electron directly (Box 2.1), it is questionable whether it is really situated at such a distance from the Cs+ cation. If true, this would represent a very extreme example of the naked anion effect (Section 3.8.2). An alternative explanation localises the electron on the Cs+ cation, which would also account for the observed low conductivity. However, convincing evidence for the separation of cation and electron comes from the nearly isostructural sodide (Na ) and kalide (K ) analogues of [Cs ([18] crown-6) 2] + -e-. In these, species the alkali metal anions are situated in the same localised cavities as their electride analogues. 

Additionally, this bonding arrangement is applicable to the cage in which hydrogen sodide (H+ Na ) was recently encapsulated [36], Here the six symbols in part 1 of Figure 3 have been replaced by 1(C1)3 groups. The... 

Compounds containing the sodide ion (Na ) have recently been made ... 

Although ihc Liilin rtairiiwi has been around for a long time, the lUPAC has noi recommended ils use previously, and Na has been universBlly called sodide. In view ct the phasirig out of terms like "cuprous" and "ferric, the introduction of hitherto unused latinized names is unexpected.]... 

The first of these was the sodide ion, Na, formed from the reaction of sodium with the cryptand N (C2H40)2C2H4)3N in the presence of ethylamine ... 

Among the intriguing developments in alkalide chemistry has been the recent synthesis of inverse sodium hydride, which contains a sodide ion, Na, and an ion encapsulated in 3 adamanzane. The H" in this structure is strongly coordinated by four nitrogen atoms in the adamanzane ligand, shown in Figure 8-8(b). 

The sodide, stable to —25°C, has been dubbed an inverse sodium hydride (see Figure 22). The strategy of using kinetically trapped cations in polyaza cages may lead to new classes of stabilized alkalides and electrides. 

Figure 22 The structure of the inverse sodium hydride 3 AdzH+Na . The sodide anion is drawn...

Na sodium sodium (general) Na+, sodium(l+) sodide (general) Na-, sodide(l—) sodide sodido Na-, sodido(l—) sodido... 

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