Alkali metals Group defined

The various metallic glasses reported in the literature [4.9] fall into a few well-defined categories (i) late transition metal + metalloid (ii) early transition metal + late transition metal or group IB metal (iii) earth alkali metal + group IB metal (iv) early transition metal + alkali metal and, (v) Actinide + early transition metal. In catalysis research, exclusively metallic glasses of categories (i) and (ii) have been used so far. Table 4.1 lists glassy metals which have been used in catalytic studies. Note that metal-zirconium alloys and Ni, Fe, and mixed Ni-Fe alloys with P and/or B as metalloid have been used most frequently. 

Some interesting effects associated to the presence of well-defined structural units appear on a broad class of binary alloys formed by mixing an alkali metal (Li, Na, K, Rb, Cs) with a tetravalent metal like Sn or Pb. Due to the large difference in electronegativities it is normally assumed that one electron is transferred from the alkali to the tetravalent atom. As the Sn- or Pb-anions are isoelectronic with the P and As atoms, which in the gas phase form tetrahedral molecules P4 and AS4, in the same way the anions group in the crystal compounds forming (Sn4)4- and (Pb4)4- tetrahedra, separated by the alkali cations. This building principle was developed by Zintl in the early thirties [1], and the presence of such tetrahedra has been detected in the equiatomic solid compounds of Pb and Sn with Na, K, Rb and Cs, but not with Li [2, 3, 4]. In this paper we focus on alkali-lead alloys. 

Cobaltic sulphate, like the sulphates of rhodium and iridium, unites with the sulphates of the alkali metals to yield a series of well-defined, crystalline salts known as alums. These are isomorphous with those of iron, manganese, chromium, and aluminium, and form an interesting link between these metals and the central vertical column in Group VIII of the Periodic Table, of which column cobalt is the first member. 

Indium and thallium form a number of binary compounds with alkali metals in which the group 13 elements form well-defined anionic clusters (Zintl ions, see Section 1-9). Examples are K8Inu (Fig. 6-3) which has considerably fewer (2n-4) electrons than the minimum described by Wade s rules (2n + 2), KgIn10Zn and K10In10M (M = Ni, Pd, Pt).6 Closo-In16 and nido-Inu clusters have also been found. Thallium, too, forms Zintl clusters Na2H contains Tlf tetrahedra, while K8T1ii is similar to In, and KT1 contains Tl octahedra.7... 

Defined 1 2 complexes with two different aluminum trialkyls in a stoichiometric ratio of 1 1 can be synthesized either from the individual components, i. e., alkali metal fluoride, AIR3 and AlRf or by reacting the 1 1 complex of a particular alkylaluminum with a stoichiometric amount of a second type of alkylaluminum. Alternatively, the varying complex formation tendency of the aluminum trialkyls can be exploited by displacing one of the alkylaluminum groups of the 1 2 complex by a stronger complexing alkylaluminum [118], for example... 

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