Metals Group IIIA

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... 

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... 

There is also a pronounced tendency for the Group IIIA metals to form metal-metal bonds and bridged structures. The electron configuration ns2 np1 suggests the possible loss of one electron from the valence shell to leave the ns2 pair intact. The electron pair that remains in the valence shell is sometimes referred to as an inert pair, and a stable oxidation state that is less than the group number by two units is known as an inert pair effect. The fact that oxidation states of +2, +3, +4, and +5 occur for the elements in Groups IVA, VA, VIA, VIIA, respectively, shows that the effect is quite common. Thus, it will be seen that the Group IIIA metals other than aluminum have a tendency to form +1 compounds, especially thallium. 

Unlike the other Group IIIA metals in the +3 oxidation state, Tl3+ is a strong oxidizing agent, and many of its compounds react to produce Tl+ compounds when heated. 

Of the oxides of the Group IIIA metals, by far the most important is aluminum oxide, A1203, because it is a widely used catalyst for many reactions. As described earlier in this chapter, there is an intimate relationship between the oxide and hydroxide in various degrees of hydration that result in the existence of the forms summarized here ... 

Of the halides of the Group IIIA metals, A1C13 is the most important and widely used. It can be prepared by the reaction... 

Although there is a considerable organic chemistry of all of the Group IIIA metals, the organic chemistry of aluminum is by far the most extensive and important. Various organic derivatives are known, and some of them are used industrially on a large scale. Several trialkylaluminum compounds are important, as are some of the mixed alkyl halides. Table 9.3 shows physical data for some of the aluminum compounds. 

Only a brief survey of the vast area of organometallic chemistry of the Group IIIA metals has been presented, but it serves to show its broad applicability. Chapter 21 deals with other aspects of the chemistry of some of the compounds described in this chapter. 

Precipitation is incomplete owing to the free mineral acid produced. If the hydrogen ions, arising from the complete ionization of the mineral acid, are removed by the addition of the salt of a weak acid, such as ammonium or sodium acetate, precipitation is almost complete. This is the basis of one of the methods for the removal of phosphates, which interfere with the precipitation of Group IIIA metals, in qualitative analysis. 

Roberts ( 1 1) surveyed the superconductive properties of the elements and recommended a critical temperature of 1.175 0.002 K for Al(cr). Since this temperature is so low, the effects of superconductivity on the thermodynamic functions are not considered. The entropy contribution due to superconductivity will be less than 0.002 J X mol . The data of Giauque and Meads (j ) and Downie and Martin (3) agree at temperatures up to 150 K but drift apart by 0.2 J X mol at 200 X and 0.17 J X mol at 300 K, with the Downie and Martin study being lower. The Takahashi (4, 5) study is even lower at 298 X. The high temperature heat capacity values are derived from the enthalpy study of Ditmars et al. (9). Their curve is intermediate between those derived from previous studies (4, 5, 6, 7, 8) and implies a flatter Cp curve near the melting point (in comparison to previous interpretations). Numerous other heat capacity and enthalpy studies are available but were omitted in this analysis. A detailed discussion of the Group IIIA metals (B, Al, and Ga) is in preparation by the JANAF staff. 

Other heat capacity and enthalpy studies are available but were excluded from this analysis. A detailed discussion of the Group IIIA metals (B, Al, and Ga) is In preparation by the JANAF staff. 

Describe some important periodic trends in the properties of Group IIIA metals and some of their compounds... 

Write equations describing general reactions of the free halogens, X2, with (a) Group lA (alkali) metals, (b) Group IIA (alkaline earth) metals, and (c) Group IIIA metals. Represent the metals as M. 

Group IIIA metals lose three electrons to form cations with noble gas configurations. 

In covalent hydrides, hydrogen and the metal are linked by a covalent bond. Aluminum, silicon, germaninm, arsenic, and tin are some of the metals whose covalent hydride structures have been stndied extensively. Some ionic hydrides, snch as LiH or MgH2, exhibit partial covalent character. The complex hydrides, such as lithium aluminum hydride and sodium borohydride, contain two different metal atoms, usually an alkali metal cation bound to a complex hydrido anion. The general formula for these compounds is M(M H4) , where the tetrahedral M H4 contains a group IIIA metal such as boron. 

Table 2.27 Summary of some physical properties of group-IIIa metals, hep = hexagonal close-packed = melting point g = crystal density.

Characterization and thermodynamics of vapor complexes of rare-earth halides with Group-IIIA metal trihalides... 

---