Silane-hydrogen mixtures

FIG. 8. (a) The total and partial pressures p and (b) the partial pressure ratio of silane and hydrogen in a silane-hydrogen mixture, at different flow ratios The total flow rate is 30 seem. (Adapted from E. A. G. Hamers. Ph.D. Thesis. Universiteit Utrecht. Utrecht, the Netherlands. 1998. with permission.)... 

Simulation of RF Discharges in Silane-Hydrogen Mixtures with the Hybrid Model... 

Fig. 2.5. Diagram showing the typical deposition conditions for microcrystalline silicon and a-Si H films deposited from silane/hydrogen mixtures at different rf power.

In a conjugated diene, where one of the carbon atoms is branched, both alkenic bonds are hydrogenated in the trifluoroacetic acid/silane reaction mixture to give the corresponding... 

Alternatively to decomposition of silane/hydrocarbon-mixtures hydrogenated amorphous Sii xCx films can be deposited from the gas phase by conventional pyrolysis, photolysis or plasma assisted decomposition of various small hydridocarbosilanes. The composition and therefore the properties of the films are known to be affected by the conditions of the... 

When silanic hydrogen (SiH) is present in the sample direct reaction as outlined above causes difficulties due to formation of a mixture of methylfluorosilanes and methylhydrogen fluorosilanes. 

The characteristic feature of these elastomers is that they are based on liquid materials which can be fabricated by injection moulding. The basic components are low viscosity materials, supplied as a two-pack system, which are blended before injection. The mixture is then cured by heating in the mould at 150-200°C. Liquid silicone elastomers are based on polydimethylsiloxanes containing vinyl groups which are cross-linked by compounds containing silanic hydrogen. In the presence of a platinum catalyst, the following addition reaction occurs ... 

Another method of manufacturing SiC by the decomposition of a gas mixture containing silane, propane, and hydrogen, and hydrogen chloride has been described (80). With such a mixture, it was possible to work at a relatively lower (1200°C) temperature and it was claimed that compact, homogeneous P SiC crystals were obtained. In a variation of this gas-phase synthesis theme, SiC has been produced from the reaction of SiCl and methane (81). SiC precipitates from 1000 to 3000°C. 

A teehnique that is a convenient source of radieals for study by EPR involves photolysis of a mixture of di-t-butyl peroxide, triethylsilane, and the alkyl bromide corresponding to the radieal to be studied. Photolysis of the peroxide gives t-butoxy radieals, whieh selectively abstract hydrogen from the silane. This reactive silicon radieal in turn abstracts bromine, generating the alkyl radieal at a steady-state eoncentration suitable for EPR study. 

The situation does not improve with mixtures with the hydrides of the elements. Thus, a detonation occurred during contact between water and chlorine due to an accidental spark. Phosphine, silane and diborane all combust spontaneously in chlorine (their behaviour is the same in oxygen). With hydrogenated nitrogenous compounds ammonia, hydrazine, hydroxylamine, ammonium salts (especially ammonium chloride), and also sulphamic acid (these last two in an acid medium) there is ignition or even detonation. 

In the plasma reactor dedicated for intrinsic material deposition (2 in Fig. 5), only hydrogen and silane are used, along with argon. A mixture of trimethylboron (5% TMB in H2), SiHa, and methane (CH4) is used in the / -plasma reactor (3 in Fig. 5). Diborane can also be used. A mixture of phosphine [PH3 (1% in H2)] and SIH4 is used in an n-plasma reactor (4 in Fig. 5). All gases are of 6.0 quality (99.9999% pure) if available from manufacturers, and otherwise as pure as possible. 

The hydrogenation of alkenes and alkynes in water can also use silanes as hydrogen sources. Tour reported that by using palladium acetate as catalyst, triethoxysilane reduced C-C unsaturated bonds to saturation in a mixture of THF and water.18 The reaction showed excellent chemo- and stereoselectivity. Water was essential to the reaction. In the absence of water, 95% of the starting alkene remained unchanged (Eq. 3.3). 

A similar dichotomy was observed in the titanium catalyzed polymerization of primary silanes coupled to the hydrogenation of norbornene (20). At low catalyst concentration (ca. 0.004H), essentially complete conversion of norbornene to an equimolar mixture of norbornane and bis-phenylsilyl- (and/or 1,2-diphenyl-disilyl)norbornane was observed. Under these conditions no evidence for reduction of titanium was obtained. At higher catalyst concentrations (> 0.02M) rapid reduction of the dimethyltitanocene to J, and 2 occurs and the catalytic reaction produces mainly polysilane (DPn ca. 10) and norbornane in ca. 80 per cent yields, and silylated norbornanes in about 20 per cent yield. 

Fiirstner and coworkers developed a new Pt- and Au-catalyzed cycloisomerization of hydroxylated enynes 6/4-141 to give the bicylo[3.1.0]hexanone skeleton 6/4-143, which is found in a large number of terpenes [317]. It can be assumed that, in the case of the Pt-catalysis, a platinum carbene 6/4-142 is formed, which triggers an irreversible 1,2-hydrogen shift. The complexity of the product/substrate relationship can be increased by using a mixture of an alkynal and an allyl silane in the presence of PtCl2 to give 6/4-143 directly, in 55 % yield (Scheme 6/4.36). 

A mixture of exo- and endo-isomers of 5-methylbicylo[2.2.1]hept-2-ene is hydrogenated with the aid of five equivalents of triethylsilane and 13.1 equivalents of trifluoroacetic acid to produce a 45% yield of < <7o-2-methylbicylo[2.2.1] heptane (Eq. 71). The same product is formed in 37% yield after only five minutes. The remainder of the reaction products is a mixture of three isomeric secondary exo-methylbicylo[2.2.1]heptyl trifluoroacetates that remains inert to the reaction conditions. Use of triethylsilane-l-d gives the endo-2-methylbicylo-[2.2.1]heptane product with an exo-deuterium at the tertiary carbon position shared with the methyl group. This result reflects the nature of the internal carbocation rearrangements that precede capture by the silane.230... 

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