Preparation of silicon-containing

In our research at MIT we have found transition metal chemistry a very useful aid in the preparation of silicon-containing ceramics by the polymer pyrolysis procedure. 

Transition Metal Compounds in the Preparation of Silicon-Containing Ceramics 271... 

Summary A brief review of the preparation of silicon containing preceramic polymers to prepare silicon carbide and silicon carbonitride fibers is given. Methylchlorodisilanes are converted to polysilanes and polysilazanes which yield ceramic fibers after meltspinning, curing, and pyrolysis. 

Successful sila-modification of several peptides leading to new protease inhibitors (03CODD526) stimulated the elaboration of synthetic methods for the preparation of silicon-containing amino acids. Among these compounds a-amino acids-containing silacycles were synthesized... 

Table 5 Preparation of Silicon-Containing Heterocycles and Spiro Compounds from Asymmetric (2-Butene-l,4-diyl)magnesium...

Scheme 5 Preparation of silicon-containing heterocycles and spiro compounds.

Preparation of silicon-containing oxetane monomers and their polymerization was also investigated by Sangermano et al. Following monomers were reported ... 

Triphosgene [35] or diphosgene [36] have been employed for the preparation of silicon-containing (52) [37], sulfur (54), and 3,6-disubstituted 2-hydroxy (or thio) pyrazine (56) chloroformates [38]. 

Amine 17 was prepared from4 by reaction with aniline at 80 °C. Treatment of 17 with mercury(II) acetate followed by borohydride reduction gave the azasilacycle (18) in modest yield (eq 9). This result is in accord with the 8-carbocation stabilizing effect of a silicon atom. Synthon 4 is thus a useful building block for the preparation of silicon-containing heterocycles. 

Related examples of silicon-containing titanocycles have also been prepared (282). These compounds are air-stable and not decomposed by methanol. When CpCpWiClOAr reacts with Grignard reagents, the aryloxy group is replaced by R, not by Cl (283). Compounds of the formula (Cp2TiR)20 prepared from (CP2TiCl)20 + RLi, where Ris CH, C2H, CgH, y)-tolyl, CgH CM2, or CH2=CH, are thermally stable and quite stable to air (283,284). 

Soluble polydiorganosilane homo and copolymers have recently shown great potential in such areas as precursors for the preparation of silicon carbide fibers (1), as photoinitiators in alkene polymerization (2), as photoconductors (3), and as positive or negative self-developing photoresists for photolithographic applications (4). A number of copolydiorganosilane copolymers have been reported recently (5) in which the copolymer contained equal amounts of both monomers in the feed. 

Preparation, characterization, and properties of silicon-containing triorganotin fluorides, both symmetrical and unsymmetrical, were investigated. It was observed that introduction of a trimethylsilyl group in the alkyl chain results in a considerable enhancement of solubility in various nonpolar solvents including dense carbon dioxide. 

Fleissman et al. (4) prepared glossy cosmetics consisting of silicone-containing polyurethanes by condensing bis-polyethylene glycol dimethicone-polypropy-lene glycol with isophorone diisocyanate. 

J.M. Silva, D.M. Dardaris, and G.C. Davis, Method of preparing transparent silicone-containing copolycarbonates, US Patent 6833422, assigned to General Electric Company (Niskayuna, NY), December 21, 2004. 

The most important class of silicon-containing polymers that have not yet been covered are the polysilazanes, shown in 7.1. These polymers, or precursors to them, are generally prepared by the reaction of organic-substituted chlorosilanes with ammonia or amines as is shown in reaction (l).32... 

Processes of this kind have some synthetic utility, since they permit exchange of silicon-containing groups from the readily prepared Si-Co compounds to other metal centres. The partial exchange of groups on silanediyl derivatives also provides a route to mixed-metal systems ... 

Flame-retardant epoxy resins with different silicon contents were prepared using silicon-containing epoxides or silicon-containing prepolymers. The thermal stability and flame-retardant properties of the produced epoxide systems were evaluated and related to the silicon content. The char yields under nitrogen and air atmospheres increased with increase in silicon content. The authors pointed out that the silicon-containing resin has improved flame retardancy over the silicon-free resin as evidenced by the LOI. LOI values increased from 24 for a standard commercial resin to 36 for silicon-containing resins.35... 

Why then write another review on the (helium I) photoelectron spectroscopy of silicon compounds At a time of rapidly increasing computer application to various aspects of preparative chemistry, it seems worthwhile to summarize historic and more recent achievements in the rapidly progressing knowledge of silicon-containing molecules, and their molecular state properties, which are via Koopmans theorem intimately connected to quantum chemical calculations. Above all, some selected cases are well-suited to illustrate... 

The synthesis of silicon-containing heterocycles was reported employing Si-C bond-forming <01JOM160> or aldehyde allylation <01TL581> reactions to prepare the metathesis substrates (Scheme 54). 

A typical embodiment for the porous layer technology is described in several patents and patent applications, e.g., a US patent application in 2006. This patent application describes a method for the preparation of silicon dioxide dispersions wherein the surface of the silicon dioxide is modified by treatment with the reaction products of a compound of trivalent aluminum with amino-organo-silane. The invention relates to recording sheets for inkjet printing having such a dispersion incorporated in the porous inkreceiving layer. Another US patent describes the preparation of nanoporous alumina oxide or hydroxide which contains at least one element of the rare earth metal series with atomic numbers 57 to 71. 

There are several reports in recent literature on the application of silicon-containing compounds as the initiators of cationic ring-opening polymerization. This apparently is related to the attempts to prepare block copolymers containing polysiloxane or polysilane segments. (CfL SiCFAgClCL system was used to initiate cationic polymerization of tetrahydrofuran... 

A series of silicon-containing spirobarbiturates 58 has been synthesized from 3,3-di(ethoxycarbonyl)-l-silacycloalkanes 57, prepared from chlor-omethyl(3-chloropropyl)silanes 56 and diethyl malonate in the presence of sodium ethylate, and urea or thiourea (64JMC695) (Scheme 12). Analogous silacycloheptyl derivatives were prepared from (4-chlorobutyl)chloro-methylsilanes similarly. 

Trimethyl(trifluoromethyl)silane can be converted into tributyl(trifluoromethyl)tin (40) in quantitative yield by treatment with bis(tributyltin) oxide in tetrahydrofuran under fluoride ion initiation. Tributyl(trifluoromethyl)tin readily trifluoromethylates disilyl sulfides at room temperature giving the corresponding trifluoromethylated di- and trialkylsilancs 41 in high yields. This method provides a new approach for the preparation of silicon-based trifluoro-methylating reagents via transtrifluoromethylation of compounds containing Si — S bonds. 

To meet the challenges of new material requirements, scientists must strive constantly to develop new systems. One recent approach has been to prepare inorganic-organic hybrid materials by using the sol-gel method common to ceramists. This technique allows a considerable range of chemistry to be used and may lead to the development of a whole array of systems that have potential applications (structural, optical, etc.). This chapter provides an overview of the general status of this approach, with emphasis on the work that comes from our laboratory. The chemistry discussed in this chapter involves the use of silicon-containing species in the preparation of polymeric network systems. 

The chapter gives a brief review of the preparation and use of silicon-containing preceramic polymers to prepare ceramic fibers. Several key issues are discussed that must be addressed if this area of technology is to continue to advance. 

The degree of substitution of the synthesized cellulose esters ranged from 0.2 (at n = 16) to 0.52 (n = 4). The hydrolytic stability of the C-O-Si bond increases with increasing n due to the shielding effect of the radicals. Thus, whereas more than 90% of the Si-O-C bonds are hydrolyzed in a preparation of trimethylsilylcellulose ( = 0) on boiling in water for 10 hours, the figure falls to 24% at n = 16 (Fig. 4). The hydrolytic stability of silicon-containing esters also increases when there are no Si-O-C bonds in the ester. A cellulose ester of this type has been prepared by the reaction of alkali cellulose with halomethyltrialkylsilanes (65) ... 

In general, sila-heterocycles are believed to be promising candidates for the development of silicon-based dmgs and agrochemicals. For example, the sila-proline ester 184 was prepared as part of a systematic study of silicon-containing amino acids and proteins <2000JOM19>. 

In addition to the head-to-tail hydrosilylation described above we could show that monomeric vinyl-functionalized hypervalent silanes can be used for the preparation of polycarbosilanes containing silicon atoms in a trigonal-bipyramidal environment [7b, 8] Treatment of... 

Another special type of silicone containing polymers is polysilazanes. These materials are used in for the preparation of high performance ceramics, silicon nitride, etc. Polysilazane can be prepared from substituted methylchlorodisilanes and gaseous ammonia in the following reaction [4] ... 

The aim of this contribution is to present data on the preparation of catalysts containing as embedding species a large family of eolloids such as colloids of ruthenium, platinum, or palladium-gold alloys and triflate derivatives such as lanthanum and silver triflate or tert-butyldimethylsilyltrifluoromethanesulfonate (BMSTM). Silica, zirconia and tantalum oxides were used as carrier. All these preparations considered the polymeric sol-gel route using as starting materials silicon, zirconium or tantalum alcoxides. 

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