Boron and Silicon

The B - C migration can also be induced by other types of electrophiles. Trimethylsilyl chloride or trimethylsilyl triflate induces a stereospecific migration to form (3-trimethylsilyl alkenylboranes having cis silicon and boron substituents.34 It has been suggested that this stereospecificity arises from a silicon-bridged intermediate. 

Addition of Boron-Silicon and Boron-Germanium Bonds 758... 

Datolite is caldiun borosilicate with a monoclinic structure (2/m) and space group P2i/c. It consists of superimposed complex sheets of linked oxygen and O, OH tetrahedra around silicon and boron atoms respectively the Si04 and B(0,0H)4 tetrahedra alternate, forming rings of four and eight tetrahedra. The natural datolite in our study consisted of seven samples from a variety of geologic environments. Concentrations of potential luminescence impurities in one sample are presented in Table 4.8. 

For the first time we have discovered transparent (painted in various colours) thread-like crystals of carbon among the products of hydrocarbon pyrolysis and during synthesis of silicon and boron carbides (Fig. 3.6) [12]. The X-ray spectral analysis has shown that the transparent threads consist of carbon (Fig. 3.7). 

Growth of anisofiopic silicon and boron carbide nanoparticles from powdered reagents was performed using a process of exothermic nanosynthesis [6,7] (Fig. 3.8). 

Diamondlike Carbides. Silicon and boron carbides form diamondlike carbides beryllium carbide, having a high degree of hardness, can also be included. These materials have electrical resistivity in the range of semiconductors (qv), and the bonding is largely covalent. Diamond itself may be considered a carbide of carbon because of its chemical structure, although its conductivity is low. 

Sulphur, selenium and tellurium are soluble in the oxychloride in the cold, but on heating, reaction may take place. Sulphur interacts to form selenium monochloride, sulphur monochloride and sulphur dioxide. Tellurium is converted into its tetrachloride. Both red and yellow phosphorus react violently with the oxychloride, forming phosphorus pentoxide and selenium mono- and tetra-chlorides. Carbon, silicon and boron are unattacked. 

The rule reqiiires that in silicates the silicon tetrahedra share no elements with each other if the oxygen-silicon ratio is equal to or greater than four. This is found t o be vrue in general (topaz, zircon, olivine, other orthosilicates), Most of the few exceptional substances now known contain extra oxygen atoms in the form of hydroxide ions. These include the clay minerals, micas, and chlorites, discussed above, and also the mineral hemimorphite, Zn[Pg.561]

Leaching Introduction of contaminants from man-made materials, such as metals from stainless steel, silicon and boron from glass, lead and tin from solder, solvents from duct tape Use of inert materials, pH control, minimization of contact time with these materials... 

Mukasyan, A. S., Characteristics and mechanism of silicon and boron combustion in nitrogen. Ph.D. Dissertation, Institute of Chemical Physics, USSR Academy of Science (1986). 

Some preliminary information is also available on the reactions of S( D) atoms with silicon and boron hydrides. 

Chromium and Nitrogen, Phosphorus, Arsenic, and Antimony—Carbides and Carbonates—Cyanides, Chromioyanidcs, Chromithiooyanates—Compounds with Silicon and Boron. 

The reaction is not restricted to phosphorus, silicon, and boron compounds the tetrameric (NSEt) is, for instance, formed from ethylamine hydrochloride and sulfur dichloride (49). Nor is it restricted to nitrogen compounds the very stable cyclic phosphinoborines are formed by elimination of hydrogen from the dimethyl-phosphine borine complex (17). 

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