Beryllium and magnesium

The hydrides of beryllium and magnesium are both largely covalent, magnesium hydride having a rutile (p. 36) structure, while beryllium hydride forms an electron-deficient chain structure. The bonding in these metal hydrides is not simple and requires an explanation which goes beyond the scope of this book. 

Alkyl derivatives of the Group 2 metals (Be, Mg, Ca, Sr, Ba) supported by poly(pyrazolyl)borato ligation have only been isolated for the lighter congeners, beryllium and magnesium. 

As with their beryllium and magnesium counterparts, the zinc alkyl derivatives [TpRR ]ZnR and [BpBut]ZnR are soluble in hydrocarbon... 

Owing to some similarities among their properties and alloying behaviour, beryllium and magnesium, metals of the 2nd group, will be presented in this chapter together with the last transition metals zinc, cadmium and mercury (see a few more remarks in 5.4). 

Beryllium and magnesium belong to the 2nd group of the Periodic Table together with calcium, strontium, barium and radium. Characteristic differences, however, may be noticed between the chemistry of Be and Mg and that of the alkaline earth s proper. Be has a unique chemical behaviour with a predominantly covalent character. The heavier elements (Ca, Sr, Ba, Ra) have a predominant ionic behaviour in their compounds. Mg has a chemistry in a way intermediate but closer to that of Be. Analogies between the Mg and Zn chemistries may also be underlined. 

The metal-donor bonds are predominantly ionic and become more labile for calcium, strontium, and barium compared to beryllium and magnesium. The solubility and stability of the complexes decrease from calcium to barium. The 1 1 adducts of NHCs with BH3 or BF3 (28 and 29) are thermally stable and can be sublimed without decomposition. This is in sharp contrast to the properties of conventional carbenes, which rely on a pronounced metal-to-ligand back donation and are, thus, not suited to forming adducts with electron-poor fragments such as... 

Although beryllium and magnesium salts do not form stable mctal-ammines yet they unite with ammonia, forming additive compounds of the hydrate type which are sometimes referred to as ammoniates or ammonio-compounds. These appear to be of the same type as the metal-anunines, and the difference seems to be merely one of stability. The ammonio-compounds are formed by the addition of ammonia gas to dry or fused salt, and most of them decompose with liberation of ammonia when dissolved in water. 

Ammino-derivatives of Beryllium and Magnesium Salts—Derivatives of Beryllium Halides—Derivatives of Magnesium Halides. 

In order to accomplish the goals of this reviewer in a logical and systematic manner, the first systems to be described will be those of aluminum derivatives that appear to be the most readily discussed in terms of their structures and bonding, followed by the Group II derivatives of beryllium and magnesium, and, finally, by a discussion of the lithium derivatives and of the mixed-metal species, which clearly represent the most difficult systems to describe properly. 

What position do beryllium and magnesium occupy in the electrochemical series of the metals ... 

What reactions occur consecutively in solutions of beryllium and magnesium salts when carbonate ions are introduced into them In what processes are beryllium and magnesium hydroxo-ions formed How can normal magesium carbonate be prepared ... 

The alkaline earth metal cations follow similar trends to the alkali metal cations in their complexation reactions with monodentate ligands. Hard , class V donor atoms are preferred, and beryllium and magnesium show a greater tendency to form complexes than do their larger congeners. 

Other anionic complexes of beryllium that have been detected are (NH4)2Be(N03)4,141 (NH4)2Be(NCS)4-MeCN and (NH4)2Be(NCS)3-MeCN.142 ESCA studies on beryllium and magnesium complexes of the type [M(NCS)4]2 and [M(CNS)3L] (L = DMF, py, MeCN) are consistent with N-bonding thiocyanate anions being present.142 The structure of K[Be(NH2)3] shows the beryllium to be in a trigonal planar unit.143... 

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