The silicon and germanium

Furthermore, the organic functionalization studies have indicated that multiple reaction products can form even for simple systems. Kinetic and thermodynamic influences must be considered in any analysis of the product distribution. Moreover, the studies have revealed differences in the dominance of kinetic vs. thermodynamic control between the silicon and germanium surfaces. The dissimilarity primarily stems from the fact that adsorbate bonds are usually weaker on Ge than on Si. This difference in energetics leads to observable differences in the degree of selectivity that can be achieved on the two surfaces. Another important motif is the significance of interdimer bonding in the products. Many molecules, even as small as ethylene, have been observed to form products that bridge across two dimers. Consequently, each analysis of adsorption products should include consideration of interdimer as well as intradimer species. 

The synthesis of chloromethyldichlorosilane, chlorometh-ylgermanium trichloride, and chloromethyldimethyltin chloride are described below as examples of the general procedure. Copper was included in the silicon and germanium runs to further improve the reaction, but it is not necessary with the halides employed herein. 

The p-RgPBsHg compounds discussed above apparently do not isomerize to the corresponding 2-substituted derivatives as the silicon and germanium derivatives do. This is not unexpected in view of the fact that the bridging phosphino-group is connected to the two basal borons by two 2-center two electron bonds as opposed to the one 3-center two electron bond which presumably binds the Group IV moieties previously discussed. 

These redistribution reactions between metal-tin complexes not only provide extremely useful transition-metal-substituted organotin chlorides, but also demonstrate the chemical robustness of the M—Sn bonds. For example, whereas the W—Sn bond in [(CO)5WSnPh3] resists attack by dry HC1, the silicon and germanium analogs are cleaved to [C1W(C0)5] 49. 

The chapter is organized as follows. In Section 2, we give a brief overview of the silicon and germanium (0 01) surfaces. Sections 3-7 cover various topics related to the dimer diffusion studies including the stability of various ad-dimer adsorption sites (Section 3), the existence of various diffusion pathways (Section 4), rotation of an on-top ad-dimer (Section 5), diffusion driven concerted motion of substrate atoms (Section 6) and intermixing (Section 7). In Section 8, we will briefly address the influence of the STM tip on the experimentally obtained activation barriers for diffusion and rotation. Finally, Section 9 contains a summary and the most important conclusions. 

This research was supported by National Science Foundation Grant CHE-8718469. The author wishes to thank the silicon and germanium community as a whole for their unending encouragement of theoretical investigations. 

Both these compounds may be prepared by the action of the appropriate tetrachloride on the Grignard reagent using a procedure identical to that used for the tin compound. The yields of the silicon and germanium compounds are 35 and 45% of theoretical, respectively, based on the metal halide. 

When the silicon and germanium salts are heated, N-demethylation occurs and the products are methyl bromide and dimethylaminomethyl-trimethylsilane. 

Figure 17.8. Illustration of the wide wavelength range of tunable gap sizes of all the silicon- and germanium-based nanotubes discussed herein for possible photoluminescence applications in optoelectronic nanodevices.

The alcoholysis reactions of tin(iv) alkoxides are comparatively faster than those of the silicon and germanium analogues and proceed to completion without any catalyst. Bradley thus prepared a number of primary, secondary and tertiary alkoxides by the alcoholysis reactions of tin tetraisopropoxide isopropanolate with various alcohols in the presence of benzene (Eq. 2.89) ... 

This chapter will deal with conducting systems, which are produced from the reaction of the silicon and germanium polymers with various dopants. Therefore, photoconducting polymers will not be involved. We shall also limit our attention to the polymers that have the silicon and germanium atoms in the main chain, but not in the side-group. 

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