Silicon nitrogen

Another possibility is to replace by nitrogen. Silicon nitride has become an increasingly important industrial product. 

Table 3 summarizes the results of an analysis of four extremely helium-rich luminous sdOs (Husfeld, 1986 Husfeld et al., in preparation). Here, only upper limits for the hydrogen abundances can be given as no traces of this element can be found in the spectra. Consequently, helium appears as the most abundant element. Significantly overabundant are also carbon (with one exception LSE 263) and nitrogen. Silicon is effectively unaltered. This abundance pattern compares well with the abundances found in the extreme helium stars of spectral type B (given in col. 6 of Table 3). However, it should be stressed that the carbon depletion in LSE 263 makes this star a peculiar object in its class.

Nitrogen-silicon bonds. The reaction of ethylenimine with chlorosil nee gives products in which the axiridine ring is attached to ailioon. 7... 

Other elements with which iron forms binary compounds, especially at higher temperatures, are boron, carbon, nitrogen, silicon, and phosphorus, l.ike FeO, these compounds often depart slightly or even considerably from daltonide composition, frequently being interstitial compounds, and in higher elements of groups VB and VIB, merging into the interstitial compound-solid solution picture which iron exhibits with the transition metals. 

III. PENTACOORDINATE NEUTRAL SILICON COMPLEXES A. Chelates with Nitrogen-Silicon Coordination... 

To test the generality of the jr-distortivity phenomenon and of the Valence Bond model for delocalization, it is of interest to apply the o-it partition to conjugated molecules other -than hydrocarbons, e.g. containing nitrogen, silicon or phosphorus atoms that we have kept in a constrained planar geometry. The total distortion energies, as well as their a and it components are displayed in Table 3, as calculated at the 6-31G/it-CI level. 

With the addition of small amounts of a third element (such as carbon, nitrogen, silicon) several new striking structures of the higher borides were found, leading to interesting properties. 

Pehlke, R. D., and J. F. Elliott High temperature thermodynamics of the silicon, nitrogen, silicon-nitride system. Trans. Met. Soc. AIME 215, 781-785 (1959). 

Another methylation method makes use of a reaction with iodomethane and a catalyst [478], as follows. About 30 mg of an oil dispersion of sodium hydride was washed three times with anhydrous diethyl ether, dried under a mild stream of nitrogen and suspended in 1 ml of freshly distilled dimethyl sulphoxide. A 200-jul portion of this suspension was added to ca. 1 /amol of phenylurea dissolved in 100 pi of pure dimethyl sulphoxide followed immediately by 50 pi of iodomethane. Reaction was allowed to proceed for 5—10 min with continuous stirring. Then 1 ml of water was carefully added and the mixture was extracted with three 1-ml portions of diethyl ether or light petroleum. The extracts were dried with anhydrous sodium sulphate, filtered and evaporated to dryness under a stream of nitrogen. Silicone stationary phases [OV-225 at 108°C or a mixture of DC-200 and QF-1 (1 3) at 170°C] were used. 

Thousands of compounds of the actinide elements have been prepared, and the properties of some of the important binary compounds are summarized in Table 8 (13,17,18,22). The binary compounds with carbon, boron, nitrogen, silicon, and sulfur are not included these are of interest, however, because of their stability at high temperatures. A large number of ternary compounds, including numerous oxyhalides, and more complicated compounds have been synthesized and characterized. These include many intermediate (nonstoicliiometric) oxides, and besides the nitrates, sulfates, peroxides, and carbonates, compounds such as phosphates, arsenates, cyanides, cyanates, thiocyanates, selenocyanates, sulfites, selenates, selenites, teflurates, tellurites, selenides, and tellurides. 

Carbodiimides are a unique class of reactive organic compounds having the heterocumu-lene structure R—N=C=N—R. They can be formally considered to be the diimides of carbon dioxide or the anhydrides of 1,3-substituted ureas, and they are closely related to the monoimides of carbon dioxide, the isocyanates. The substituent R can be alkyl, aryl, acyl, aroyl, imidoyl or sulfonyl, but nitrogen, silicon, phosphorous and metal substituted carbodiimides are also known. The unsubstituted carbodiimide HN=C=NH is isomeric with cyanamide, H2NCN. Mono substituted carbodiimides, generated in the thermolysis of 1-substituted tetrazoles, can be isolated at liquid nitrogen temperature but isomerize to the cyanamides at higher temperatures. ... 

The crystal structure shows three four-membered (SiNLiN)-ring systems which are planar. Although the nitrogen silicon angles are normally near 120 , the (SiNSi)-angles in this molecule are much larger. 

Precursors that release stoichiometric silicon ifitride in an inert gas atmosphere and which therefore avoid segregation of silicon metal can be obtained by coammonolysis of dichlorosilane and trichlorosilane. - Such polymers exhibit nitrogen silicon ratios greater than 4 3. Compared to [SiH2NH] copolymers [SiH2NH] ,[SiH(NH)i 5] are more highly cross-linked, but in contrast to [Si(NH)2l , they are processable. 

I. Inorganic siloxane, sulfur chains, black phosphorus, boron-nitrogen, silicones. 

An important question concerning the nitrogen chemical shifts of aminosilanes is whether the spectral data can give indications of the existence of nitrogen-silicon donor-acceptor bonds. (87, 88) In the case of two silatranes [1] a high-frequency shift of about 9 ppm has been... 

Gilpin, L.C., Davidson, K. and Roberts, E.C. The influence of changes in nitrogen silicon ratios on diatom growth dynamics. Journal of Sea Research (accepted, 2003). 

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