Silicon framework

For the last few years we have tried to synthesize larger two-dimensional silicon frameworks. We wanted to find out how large a molecule must be in order to show delocalization effects of electrons as in elemental silicon. It is well known that radical anions are possible in simple cyclosilanes in which the additional electron is completely delocalized in the cycle [11]. 

The cyclohexasilane ring of trans-lfl has a chair form and both chlorine atoms occupy axial positions. The cyclotetrasilane ring has a folded structure with the fold angles of 33.0 and 33.6°. The structure of the silicon framework of trans-lfl resembles that of bicyclo[4.2.0]octane, in which the cyclohexane ring has a chair form and the cyclobutane ring has a folded structure.67... 

Nesper R, Currao A, Wengert S (1996) Silicon frameworks and Electronic structures of novel solid silicides. In Auner N, Weis J (eds) Organosilicon Chemistry. Wiley-VCH,... 

The British scientist wondered whether he could produce similar substances based on a silicon framework. His efforts inadvertently planted the seeds of an idea that has since blossomed in the mind of many science fiction writers an alien world may exist where everything is based on the chemistry of silicon instead of carbon. Kipping, however, by his own admission, did not think that he had come up with anything dramatic. He produced a variety of oils and gunks, which he... 

All-anti-octasilane 327 (Figure 20) composed of two bicyclic trisilane units with trimethylsilyl groups at the termini was prepared and its structure was confirmed by X-ray crystal structure. The spectroscopic data demonstrated the effective (T-delocalization over the silicon framework <2006JA6800>. 

Silicon Frameworks and Electronic Structures of Novel Solid Silicides... 

The large set of older and novel silicides provides a fascinating supply for silicon linkages from molecular to polymeric character in one, two, and three dimensions. Silicides have been used to perform topochemical reactions preserving at least partially the silicon framework. Numerous investigations on CaSi2 date back more than 50 years until the late 70 s [49, 50]. 

Figure 14, Postoperative appearance of the same child shown in Figure 13 following ear reconstruction with the silicone elastomer implant. His own subcutaneous tissue and skin were shaped around the silicone framework during the process of ear reconstruction.

Fig. 2.14 Phase relations for BagNUSi46-x-y at 1,000 °C. Analysis of the equilibrium phases after annealing clearly shows the deviation of the homogeneity range from the iso-concentration line describing the composition BagNixSi46 x and hence the presence of defects in the silicon framework [83]...

On the basis of theoretical calculations, the highdimensional silicon framework results in a smaller bandgap than that of the low-dimensional one [19,20]. In order to reduce the bandgap of the polysilanes, tiie synthesis of branched polysilanes, poly(organosilynes), has been attempted. 

Until now the double-quantum coherence spectroscopy has not often been used for silicon frameworks. In double-quanmm coherence spectroscopy the silicon nucleus is almost ten times as sensitive as the C nucleus because of the higher natural abundance of Si (4.7% compared with 1.1% C). Disadvantages of the Si nucleus are the long relaxation times T i) and the negative nuclear Overhauser effect (NOE). In practice, this means that a very long recording time is necessary unless a relaxation reagent such as Cr(acac)3 is used. 

Si—C bond (equation 35). The reasons for the diffeent behavior of 23 toward lithium remain unclear. It was, however, suggested that the facile formation of 24 is due to its thermodynamic stabilization by electron delocalization into the silicon framework. ... 

This effect is referred to as pseudo-luminescence. In fact, the glass fibers are gradually leached selectively to the extent that ultimately only a naked silicon framework is left [814], [815], [816], [817]. 

The structure (which incidentally is that of the silicon framework in ThSi2) is likely to have a density between diamond and graphite. It is calculated, unreliably, to be 17 kcal/mole of C unstable relative to diamond. And predicted to be metallic. These two predictions are connected to each other. 

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