Germanium ions

Let us consider the corrosion of p-type germanium in aqueous solution. The anodic reaction of germanium corrosion is the transfer of germanium ions involving holes in the valence band and its overall reaction may be expressed by... 

Germanium-ion clusters/complexes Table 24.3.2 BDEs in Germanium-Ion Clusters/Complexes ... 

The oxidation of M(Por)Fe(CO)4 is irreversible in the sense that there are no coupled peaks associated with reduction of [M(Por)Fe(CO)4]. Similar voltammograms were obtained for the six M(Por)Fe(CO)4 complexes and peak potentials for the single irreversible oxidation at an Au electrode are listed in Table 19. As expected, the OEP complexes are easier to oxidize than the TpTP and TmTP complexes. Also, with a given porphyrin ligand the oxidation is easier for the Ge complex than for the Sn complex. This is due to the higher electronegativity of the germanium ion. 

Recently the method described in this paper has also been applied to Germanium. The ionic potential used is the Topp-Hopfield form [lO] with parameters determined by the Germanium ion. The calculated lattice constant is 5.517 K to be compared with the experimental value of... 

There are a lot of defects in the germanium-doped core. The paramagnetic Ge( ) defects, where n refers to the number of next-nearest-neighbour Ge atoms surrounding a germanium ion with an associate unsatisfied single electron, were first identified by Friebele et al. These defects are shown schematically in Fig. 8.3. 

Silicon, germanium, tin and lead can make use of unfilled d orbitals to expand their covalency beyond four and each of these elements is able (but only with a few ligands) to increase its covalency to six. Hence silicon in oxidation state -f-4 forms the octahedral hexafluorosilicate complex ion [SiFg] (but not [SiCl] ). Tin and lead in oxidation state -1-4 form the hexahydroxo complex ions, hexahydroxostannate(IV). [Sn(OH) ] and hexahydroxoplum-bate(IV) respectively when excess alkali is added to an aqueous solution containing hydrated tin(IV) and lead(IV) ions. 

Germanium forms both a difluoride and a tetrafluoride. It also forms a stable hexafluorogermanate complex ion, GeF that is present in the aqueous acid and a number of salts. 

Silicon (3), which resembles metals in its chemical behavior, generally has a valence of +4. In a few compounds it exhibits a +2 valence, and in silicides it exists as a negative ion and largely violates the normal valency rules. Silicon, carbon, germanium, tin, and lead comprise the Group 14 (IVA) elements. Silicon and carbon form the carbide, SiC (see Carbides). Silicon and germanium are isomorphous and thus mutually soluble in all proportions. Neither tin nor lead reacts with silicon. Molten silicon is immiscible in both molten tin and molten lead. 

Use Appendix 2D to find the values for the atomic radii of germanium and antimony as well as the ionic radii for Ge2+ and Sb3+. What do these values suggest about the chemical properties of these two ions ... 

Germanium forms a series of anions called germides. In the germide ion Ge4" the four Ge atoms form a tetrahedron in which each atom is bonded to the other three and each atom has a lone pair of electrons. What is the value of n, the charge on this anion Explain your reasoning. 

Identify the oxidation number of germanium in the following compounds and ions (a) GeQ44 (b) K4Ge4Te,0 ... 

As we can see from the last entry in this table, we have deduced only a rule. In InBi there are Bi-Bi contacts and it has metallic properties. Further examples that do not fulfill the rule are LiPb (Pb atoms surrounded only by Li) and K8Ge46. In the latter, all Ge atoms have four covalent bonds they form a wide-meshed framework that encloses the K+ ions (Fig. 16.26, p. 188) the electrons donated by the potassium atoms are not taken over by the germanium, and instead they form a band. In a way, this is a kind of a solid solution, with germanium as solvent for K+ and solvated electrons. K8Ge46 has metallic properties. In the sense of the 8-A rule the metallic electrons can be captured in K8Ga8Ge38, which has the same structure, all the electrons of the potassium are required for the framework, and it is a semiconductor. In spite of the exceptions, the concept has turned out to be very fruitful, especially in the context of understanding the Zintl phases. 

Polymeric forms have also been reported. One example, which also includes germanium heteroatoms terminating the chain, is the oligomer (RO)Ge(RO)2Co(RO)2Co(RO)2Ge(OR), (97) where each Co center is surrounded by four bridging tert-butoxide ions.416 These form via a photochemically induced labile solvent complex, or else through thermally induced substitution... 

Harbuck, D. D. Judd, J. C. Behunin, D. V. Germanium solvent extraction from sulfuric acid solutions (and co-extraction of germanium and gallium). Solvent Extr. Ion Exch. 1991, 9, 383-401. 

Carbon, silicon, and germanium neither lose nor gain. They share electrons with other atoms. Tin and lead are too large to form the close electron-sharing bonds of the other three. They lose electrons to form +2 or + 4 ions. 

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