Group IIIA

Aluminum forms a complete series of AlYX compounds (Y = S, Se, Te X = Cl, Br, I). Furthermore, a number of compounds with Se(IV) and Te(IV) are known, such as TeClJ AlClj (197) and SeCl AICI4 (364), which are not considered here. A borderline case consists in the reduced phases found in the systems (TeCl4-l-4AlCl3)-Te and (SeCl4 + 4A1C13)-Se (88), e.g., Te (AlClr) (89), T + (AUClf) (89), Te + (AICID3 (88), Se (AlClr) (88), and Se + (AICID (87), which contain cyclic polytellurium and polyselenium cations. For a detailed review of homopoly atomic ions of the posttransition elements, see (86). 

The compounds AlYX are best prepared by direct reaction between the respective aluminum halide and chalcogenide in a sealed ampoule at 350°C. The reaction is complete after 2 weeks. In the case of the iodides, a mixture of A1 and I2 (molar ratio 3 10) is used instead of AII3. Other preparative methods, such as the reaction of an aluminum halide with Zn or Cd chalcogenide, or with the chalcogen itself, are applicable to the bromide and chloride only, and give poor yields (15-20%) (158, 159, 266, 327, 328). 

Growth of single crystals. Crystals of the aluminum selenide halides (needles, maximum length 15 mm) were grown by vapor transport in sealed ampoules between two temperatures (380 and 320°C for Al-SeCl, and 350 and 300°C for AlSeBr and AlSel) over a period of two months. A large excess of the halogenide was used (266). 

AlSCl has an orthorhombic structure, with the lattice constants a - 8.09, b = 10.52, c = 3.86 A, and Z = 4. It is probably isotypic with SbSCl and BiSCl, crystallizing in a layer type of lattice (157) (see Section XII,C,5). The selenide halides are monoclinic, with the probable space-group P2i/m. The lattice constants are given in Table XVII. The constancy of the b parameters for all three compounds suggests the general presence of an Al-Se chain extending in that direction (266). 

Structural data, except powder patterns, for the other compounds are not known. 

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Group III. Compounds insoluble in water, but soluble in dilute sodium hydroxide. This group may be further subdivided into Group IIIA—soluble in dilute sodium hydroxide and soluble in dilute sodium bicarbonate and Group IIIB—soluble in dilute sodium hydroxide and insoluble in dilute sodium bicarbonate. 

Again, the complete series of InYX compounds (Y = S,Se,Te X = Cl,Br,I) exists. Of the Group IIIA chalcogenide halides, the indium compounds have been the most extensively studied. 

Group IIIA (3). Scandium, Yttrium, Lanthanoids, Actinoids... 

The lanthanides are congeners of the Group IIIA metals scandium and yttrium, with the +3 oxidation state usually being the most stable. These ions are strong oxyphilic Lewis acids and catalyze carbonyl addition reactions by a number of nucleophiles. Recent years have seen the development of synthetic procedures involving lanthanide metals, especially cerium.195 In the synthetic context, organocerium... 

Group IIIA metals, however, like aluminum, will not precipitate in an acidic hydrogen sulfide solution. They will precipitate, however, if a basic hydrogen sulfide solution is introduced. Group LA metals, on the other hand, are always soluble in a hydrogen sulfide solution, regardless of whether the solution is acidic or... 

FIGU RE 6.5 Boiling points of group IIIA and IVA halides. 

The organometallic chemistry of other members of group IIIA is relatively much less important than that of aluminum. There is an extensive organic chemistry of aluminum, and some of the compounds are commercially important. For example, triethylaluminum is used in the Ziegler-Natta process for polymerization of alkenes (see Chapter 22). 

Alkyls of group IVA elements are essentially unreactive in air, but group IIIA alkyls are extremely reactive. Provide an explanation for this great difference in behavior. 

The reference material is usually elemental indium, a soft metal (atomic number 49 in group IIIA in the periodic table). One small plug of indium is placed in an aluminum crucible, which is then positioned... 

Uses. Large quantities of Sb metal have been used mainly in alloys with Pb (battery grids) and other metals. Alloys are the predominant use of antimony because its brittleness bars direct use. High purity antimony (>99.999%) has a limited but important application in the manufacture of semiconductor devices. When alloyed with elements of 13th group (IIIA), the III-V compounds are formed these have important applications as infrared devices, diodes and Hall effect devices. Also used for fireworks and thermoelectric piles. 

The minimum oxygen concentration for explosion of most volatile hydrides of Group IIIa-Va elements is nearly zero, so complete exclusion of air or oxygen is essential for safe working. Presence of impurities in hydride mixtures further increases the danger of ignition. 

Indium is a group IIIA metal and is a congener of aluminum. Considerable interest has developed recently in the synthetic application of organoindium reagents.145 One of the properties that makes them useful is that the first oxidation potential is less than that of... 

Surface Acid-Base Characterization of Containing Group IIIA Catalysts by Using Adsorption Microcalorimetry... 

Measurement of Acid-Base Interactions in Group IIIA Containing... 

In all above mentioned applications, the surface properties of group IIIA elements based solids are of primary importance in governing the thermodynamics of the adsorption, reaction, and desorption steps, which represent the core of a catalytic process. The method often used to clarify the mechanism of catalytic action is to search for correlations between the catalyst activity and selectivity and some other properties of its surface as, for instance, surface composition and surface acidity and basicity [58-60]. Also, since contact catalysis involves the adsorption of at least one of the reactants as a step of the reaction mechanism, the correlation of quantities related to the reactant chemisorption with the catalytic activity is necessary. The magnitude of the bonds between reactants and catalysts is obviously a relevant parameter. It has been quantitatively confirmed that only a fraction of the surface sites is active during catalysis, the more reactive sites being inhibited by strongly adsorbed species and the less reactive sites not allowing the formation of active species [61]. 

The measurement of heats of adsorption by means of microcalorimetry has been used extensively in heterogeneous catalysis in the past few decades to gain more insight into the nature of gas-surface interactions and the catalytic properties of solid surfaces. Specific attention will be focused on group IIIA containing samples in this section. 

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