Germanium deficiency

There is no known biological requirement for germanium, germanates or any organoger-manium compounds. Germanium deficiency has not been demonstrated in any animal5. 

Peng X, Lingxia Z, Scheauzee GN and Xiong G (2000) Selenium, boron, and germanium deficiency in the etiology of Kashin-Beck disease. Biol Trace Elem Res 77 193-197. 

In fact, additions of tributylgermyl radical and tributyltin radical to activated alkenes occur at about the same rate (see refs, 38 and 101). This addition reaction is probably more readily reversible in the case of tin (because a weaker bond is formed) and therefore hydrostannylation is a less serious problem than hydrogermylation. Thus, very reactive precursors (preferably iodides) are required as precursors if germanium hydride is used with an electron deficient alkene but this is not because the germanium radical is less reactive towards halides than the tin radical. 

Photoluminescence of Oxygen-Deficient Defects in Germanium Oxides. . . 108... 

In substoichiometric germanium oxides, Ge02 x, the insufficiency of oxygen atoms can result in the formation of oxygen-deficient defects. The most typical of these defects is the so-called E -center (-Ge=) defect, which can also be combined with OV located in its nearest neighborhood. The E -center and the E -OV combination exhibit peculiar optical properties considered in this subsection. 

This is confirmed by a very similar homologous germylene compound [85] that has two annulated quinoxaline units on an eight-membered germylene ring system. There, the germanium centre is sufficiently electron deficient to ligate a chloride anion, i.e. it acts as an electrophile not as a nucleophile. 

The electron deficiency model implies that etch stop should not occur on n-Si where there are abundant electrons in the conduction band. Unable to explain the etch rate reduction on phosphorus- or germanium-doped n-Si, Seidel et al suggested that the etch rate reduction observed on phosphorus-doped n-Si is caused by a different mechanism. Also, the electron deficiency model assumes that electrochemical reactions are responsible for the etching process in alkaline solutions. However, experimental results indicate that the etching process is mainly of chemical nature as described in detail in Chapter 5. 

Fischer-type carbenes are known as potential carbene transfer reagents to electron-rich and electron-deficient alkenes. Little is known about the chemistry of carbene complexes with silicon substituents at the carbene C-atom, whereas complexes with germanium, tin, or lead have not yet been prepared. The tungsten-carbene complexes 6 react with an excess of ethyl vinyl ether to give l,2-diethoxy-l-(trialkylsilyl)cyclopropanes 7." Only the f-isomers were formed and similar results can be achieved by using the corresponding molybdenum or chromium complexes. On the other hand, no reaction takes place with 2,3-dihydrofuran or ethyl ( )-but-2-enoate. ... 

For the attachment and the traceless release of electron-deficient aromatics, germanium-based hnkers of type 89 (Fig. 10) have been developed [103, 104]. This linker has the advantage that it is fairly stable towards strongly basic conditions and strong nucleophiles. 

What is more, the asymmetric structure of the surface dimers in silicon and germanium causes a polarization of the double bond. Hence may occur a nucleophilic attack on the Ji -orbital and the formation of a rr-complex from the attacking, electron rich alkene and the electron-deficient end of the surface dimer. The subsequent addition leading to the final product is easy to take place then (Figure 6.43). Obviously this is not the concerted and symmetric mechanism typical of pericyclic reactions, which is also why the prohibition of a thermal reaction is by-passed. 

Kashin-Beck Disease (KBD), a condition characterized by collagen breakdown and joint deterioration, was the second human disease to be associated with selenium deficiency (Dongxu 1990). Seasonal incidence variations suggest the involvement of infectious agents and of mycotoxins, as well as deficiencies of certain other trace elements (iodine, boron, germanium) (Dongxu 1990, Peng et al. 2000). 

Photosensitivity results from high temperature drawing of germanium doped fiber preforms. Oxygen deficient centers are present which, when irradiated with UV light, cause an increase in the core index. This effect can be increased by hydrogen doping of the fiber prior to... 

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