Heavier -/-block metals

Some heavier / -block metals form molecular hydrides similar to those of nonmetals in the same group, examples being digallane (Ga2H6) and stannane (SnH4), both of very low stability. 

In this section, we introduce the first group of cluster compounds of the heavier -block metals in which the external ligands are halides. Octahedral Mg frameworks are present in most of these clusters, but, in contrast to similar group 5 and 6 species (Sections 23.6 and 23.7), most zirconium clusters are stabihzed by an interstitial atom, e.g. Be, B, C or N. 

Data are given for the p- and first row -block elements. The ionic radius varies with the charge and coordination number of the ion a coordination number of 6 refers to octahedral coordination, and of 4 refers to tetrahedral unless otherwise specified. Data for the heavier -block metals and the lanthanoids and actinoids are listed in Tables 23.1 and 25.1. 

Elements on the left of the p block, especially the heavier elements, have ionization energies that are low enough for these elements to have some of the metallic properties of the members of the s block. However, the ionization energies of the p-block metals are quite high, and they are less reactive than those in the s block. The elements aluminum, tin, and lead, which are important construction materials, all lie in this region of the periodic table (Fig. 1.61). 

Of course, it is not without precedence as there are already various reviews and textbooks in the area. Most closely related to this work are the reviews by Setzer and Schleyer and by Weiss °. A textbook edited by Sapse and Schleyer contains chapters on various topics of lithium chemistry. Three reviews by StaUce, Harder and by Jutzi and Burford concentrate on cyclopentadienyl organometallic derivatives, containing also the s-block derivatives. Two reviews deal with the heavier alkali metal organics, the first written by Schade and Schleyer , the second by Smith . There are several chapters on lithium organics within more general metal organic publications ... 

Heavier p-block metals often occur with an oxidation state 2 less then the group value... 

The flexibility of the x-block coordination sphere is particularly evident with heterometallic clusters. This is strikingly evident in the mixed Li-heavier alkali metal t-butoxides [(Bu 0)gLi4M4] (M = Na, K, Rb, Cs), which form a structurally authenticated homologous series. They are... 

This simple model depends on the properties of a deformable core, and is only likely to be significant for heavier, polarisable metals. In addition, there are the directional influences of the valence orbital overlaps, which have been widely explored, and, in general, favour cis geometry in the d-block. For example, the Extended Huckel calculations of Tatsumi and Hoffmann show the dominant role of 4d-n orbitals in stabilising the cis geometry in MoO + [75]. In this... 

First row d-block metal ions are found dominantly in the M(II) or M(III) oxidation states. Heavier members of the d block tend to prefer higher oxidation states. 

Housecroft, C.E. (1999) The Heavier d-Block Metals Aspects of Inorganic and Coordination Chemistry, Oxford University Press, Oxford, UK. One of few textbooks devoted to exemplifying differences between the coordination chemistry of different rows of the d block. 

In this section, we consider physical properties of the J-block metals (see cross references in Section 19.1 for further details) an extended discussion of properties of the heavier metals is given in Section 22.1. Nearly all the J-block metals are hard, ductile and malleable, with high electrical and thermal conductivities. With the exceptions of Mn, Zn, Cd and Hg, at room temperature, the metals possess one of the typical metal structures (see Table 5.2). The metallic radii (rjnetai) for 12-coordination Table 5.2 and Figure 19.1) are much smaller that those of the -block metals of comparable atomic number Figure 19.1 also illustrates that values of /-metal ... 

Chapter 21 dealt with descriptive chemistry of the first row fi -block metals and, in this chapter, the theme continues with the focus being the second and third row metals (the heavier metals). Reasons for discussing the lighter and heavier metals separately were given in Section 21.1. 

Figure 22.1 shows the relative abundances of the second and third row J-block metals. Compared with the first row metals (Figure 21.1), the abundances of some of the heavier metals... 

Some physical properties of the heavier J-block metals have already been discussed or tabulated ... 

In this section, we introduce the first group of cluster compounds of the heavier J-block metals in which the... 

Studies of the heavier i -block metals are often used to introduce students to (a) metal-metal bonding, (b) high coordination numbers, (c) metal halo clusters and (d) polyoxometallates. Write an account of each topic, and include examples that illustrate why the first row metals are not generally as relevant as their heavier congeners for such discussing these topics. 

Similarly, ligands with hard N- or O-donor atoms form more stable complexes with light s- and p-block metal cations (e.g. Na+, Mg +, Al ), early block metal cations (e.g. Sc, Cr, Fe +) and /-block metal ions (e.g. Ce, Th ). On the other hand, ligands with soft P- or 5-donors show a preference for heavier p-block metal ions (e.g. Tl +) and later block metal ions (e.g. Cu" ", Ag+, Hg +). 

Figure 23.1 shows the relative abundances of the second and third row fif-block metals. Compared with the first row metals (Figure 22.1), the abundances of some of the heavier metals are very low, e.g. Os, 1 x 10 ppm and Ir, 6 x 10 ppm Tc does not occur naturally. Yttrium and lanthanum are similar to the lanthanoids and occur with them in nature. The major yttrium and lanthanum ores are monazite (a mixed metal phosphate, (Ce,La,Nd,Pr,Th,Y... )P04) and bastndsite... 

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