Germanium preparation

Reaction (1) is similar to that used for the preparation of other volatile chlorides (BC13, TiCl4) reaction (2) has already been mentioned in connection with the recovery of germanium. Preparations of SnBr4 and Snl4 from the elements are also convenient. 

Aldol reactions Enolates are formed from a-bromo carbonyl compounds on reaction with germanium (prepared in situ from Gel and K). The aldol reaction is jyn-selective. 

Nagata N, Yoneyama T, Yanagida K, Ushio K, Yanagihaea S, Matsubaea O and Eishi Y (1985) Accumulation of germanium in tissues of a longterm user of germanium preparation died of acute renal failure. J Toxicol Sci 10 333-341. 

In humans, germanium is widely distributed throughout the body. Hamilton et al. [28] found the highest germanium concentrations in kidney (5 p,g/g fresh tissue) and lower ones in brain (0.1 xg/g fresh tissue). In users of germanium preparations, particularly high accumulations of this element were found in spleen, renal cortex, brain, and skeletal muscle [29], as well as in hair and nails [30]. 

Organic germanium preparations are biotransformed by the liver microsomal cytochrome P-450 enzyme system, probably through a C-hydroxylation mechanism [31]. Most germanium (>90%)... 

Figure 2.9 Bright-field TEM images of amorphous thin films of (a) silicon and (b) germanium prepared by evaporation. The corresponding electron diffraction patterns are shown in the insets.

The product is a solid yellow hydrated oxide. If prepared by a method in the absence of water, a black anhydrous product is obtained. Germanium(II) oxide is stable in air at room temperature but is readily oxidised when heated in air or when treated at room temperature with, for example, nitric acid, hydrogen peroxide, or potassium manganate(VII). When heated in the absence of air it disproportionates at 800 K ... 

Germanium(IV) oxide occurs in two forms one has a rutile lattice and melts at 1359 K whilst the other has a quartz lattice and a melting point of 1389 K. It can be prepared by oxidation of germanium using, for example, concentrated nitric acid, or by the hydrolysis of germanium tetrachloride ... 

Germanium forms divalent compounds with all the halogens. Germaniunil 1) chloride can be prepared by passing the vapour of germanium(IV) chloride (see below) over heated germanium. The reaction is reversible and disproportionation of germanium(II) chloride is complete at about 720 K at atmospheric pressure ... 

Germanium(II) fluoride can be prepared by a similar process using a slightly lower temperature.)... 

Germaniiimil V) chloride can be prepared by passing chlorine over germanium at a temperature of 370 50 K ... 

Characterization of Germanium PhosphosUicate Films Prepared by MCVD," presentation, at the faU meeting of the American Ceramic Society, 1981, Bedford, Pa, 1981. 

Germanium difluoride can be prepared by reduction (2,4) of GeF by metallic germanium, by reaction (1) of stoichiometric amounts of Ge and HF in a sealed vessel at 225°C, by Ge powder and HgF2 (5), and by GeS and PbF2 (6). Gep2 has been used in plasma chemical vapor deposition of amorphous film (see Plasma TECHNOLOGY Thin films) (7). 

Germanium monoxide [20619-16-3], GeO, can best be prepared in pure form by heating a mixture of Ge and Ge02, in the absence of oxygen. At temperatures above 7I0°C, GeO sublimes from the mixture and condenses as a glassy deposit in the cooler part of the reaction vessel. Germanium monoxide is stable at room temperature. 

Miscellaneous Inorganic Compounds. Germanium nitride [12065-36-0], Ge N, is about as inert as tetragonal Ge02. It is prepared most... 

AH intrinsic germanium metal sold is specified to be N-type with a resistivity of at least 40 H-cm at 25°C or 50 H-cm at 20°C. Germanium metal prepared for use in infrared optics is usuaHy specified to be N-type with a resistivity of 4-40 Hem, to be stress-free and fine annealed, and to have certain minimum transmission (or maximum absorption) characteristics in the 3—5 or 8—12 pm wavelength ranges. Either polycrystaHine or single-crystal material is specified. 

Analysis of refined germanium products is done in a wide variety of ways, including several methods that have become ASTM standards (47). Electronic-grade Ge02 is analyzed using an emission spectrograph to determine its spectrographic purity. Its volatile content is measured in accord with ASTM F5 and its bulk density with F6. Other ASTM standards cover the preparation of a metal biHet from a sample of the oxide (F27), and the determination of the conductivity type (F42) and resistivity (F43) of the biHet. 

Germanium metal is also used in specially prepared Ge single crystals for y-ray detectors (54). Both the older hthium-drifted detectors and the newer intrinsic detectors, which do not have to be stored in hquid nitrogen, do an exceUent job of spectral analysis of y-radiation and are important analytical tools. Even more sensitive Ge detectors have been made using isotopicahy enriched Ge crystals. Most of these have been made from enriched Ge and have been used in neutrino studies (55—57). 

The reaction of HCl and silicon, germanium, and boron hydrides is cataly2ed by aluminum chloride and is useful for preparing chloro-substituted silanes andgermanes. 

DiaLkyl peroxides may be prepared by reaction of alcohols or alkyl trifluoromethanesulfonates with organomineral peroxides of siUcon, tin, and germanium (44,108), where Q = Sn and Ge ... 

The polymetallosiloxanes above may in fact be considered as variants of a series of polymetalloxanes which are akin to the silicones but which contain, for example, tin, germanium and titanium instead of silicon. Of the poly-organostannoxanes, dibutyl tin oxide finds use as a stabiliser for PVC and as a silicone cross-linking agent. Polyorganogermanoxanes have also been prepared (Figure 29.13). 

In some materials, semiconductors in particular, interstitial atoms play a crucial role in diffusion. Thus, Frank and Turnbull (1956) proposed that copper atoms dissolved in germanium are present both substitutionally (together with vacancies) and interstitially, and that the vacancies and interstitial copper atoms diffuse independently. Such diffusion can be very rapid, and this was exploited in preparing the famous micrograph of Figure 3.14 in the preceding chapter. Similarly, it is now recognised that transition metal atoms dissolved in silicon diffuse by a very fast, predominantly interstitial, mechanism (Weber 1988). 

Germanium phthalocyanine (PcGeCl2), similar to silicon phthalocyanine, is prepared from isoindolinediimine and germanium(IV) chloride in quinoline.105,1 10,1 53 Besides this common procedure, it can also be prepared by metal insertion into PcH2 starting from germanium(IV) chloride in dimcthylformamidc.141 The diol can be obtained by reprecipitation from concentrated sulfuric acid. 

The state of the synthetic art in this area, in 1979, is much more satisfactory. During the past decade, several new synthetic developments have occurred such that we are closer to the point where the limitations upon synthesis of trifluoromethyl compounds are related more to stability problems in isolated cases, and are not nearly so much due to lack of widely applicable synthetic techniques. We find ourselves, for example, in a position in 1979 where the germanium compound, Ge(CF3)4, which in the past decade, was considered by many workers to be of insufficient stability to permit isolation, has been prepared by four independent methods and is known to be stable to over 100°C. Many of these new synthetic techniques have emerged from studies conducted in our laboratory at the University of Texas and previously... 

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