Metal salts Metastable structure

Metastable solutions of GaX (X = C1, Br) as well as conventionally prepared Gal react with lithium or sodium organometallics in standard salt metathesis reactions with formation of M2R4 (Section 3.07.4.1) as well as neutral and anionic clusters of the type MnRm]x m > n) (chapter 4.1). Moreover, metalloid clusters [MnRm]x (m < n), which feature different types of metallic core structures, have been obtained. Their formation strongly depends on the reaction conditions, in particular the reaction temperature, and the (donor) solvent. 

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 order to prepare metastable states or possibly new phases of nano-scale metal particles, low temperature, kinetic growth methods should be used.(4J And atoms should be used, rather than salts or oxides since in the former case the high temperature reduction step can be avoided. In actuality, in recent years we have witnessed the development of several methods for the low temperature kinetically controlled growth of clusters from free atoms. Perhaps the most dramatic development has been the "cluster beam" approach where evaporated metal atoms are allowed to cluster in low temperature gaseous helium or argon streams.(5-2(9) Unusual cluster structures and reactivities have been realized. 

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