Si-Cl bonds

Methylchlorodisilanes are by-products of the dkect-process residue, commonly called high boiling point residue or simply residue, and are formed in about 4% of the total (CH2)2SiCl2 produced, which in 1994 was about 30,000 tons per year. Disilanes are key constituents of the residue, and novel reactions forming Si—Cl bonds have been described (44,45). Some chemical reactions of dkect-process disilanes are shown in Figure 2. Cleavage chemistry of Si—Si compounds with HCl practiced industrially has also been described (47). 

Synthesis of Silicone Monomers and Intermediates. Another important reaction for the formation of Si—C bonds, in addition to the direct process and the Grignard reaction, is hydrosdylation (eq. 3), which is used for the formation of monomers for producing a wide range of organomodified sihcones and for cross-linking sihcone polymers (8,52—58). Formation of ether and ester bonds at sihcon is important for the manufacture of curable sihcone materials. Alcoholysis of the Si—Cl bond (eq. 4) is a method for forming silyl ethers. HCl removal is typically accomphshed by the addition of tertiary amines or by using NaOR in place of R OH to form NaCl. 

According to these results the yields and E. F. decrease with the increasing number of Si-Cl bonds in the functional initiators. It is possible that Si-Cl bonds may slowly react with the diethylaluminum chloride coinitiator and thus reduce the expected E.F. as follows40 ... 

It is also possible that Si-Cl bonds may be consumed slowly by chain transfer process as follows41 42) ... 

Although the effective functionality of CISi-PaMeSt was less than one, attempts were made to obtain block copolymers by coupling with living polyisoprenyllithium and a,w-disodium polyisobutylene glycolate. These particular coupling reactions were selected because it is known that Si-Cl bonds readily react with organolithium compounds and sodium alkoxides43 45 . 

Si-H containing functional initiators have been obtained by reduction with LAH of the corresponding Si-Cl containing compounds. Conditions have been developed under which the benzylic chloride remains unchanged while the Si-Cl bond is converted to Si-H (for experimental details see Sect. H.C.). The initiators obtained are shown in Table 1. 

Another class of silicon-containing polymers that have great potential to be extremely useful precursor materials are poly(chlorocarbosilanes).14f 46 Poly (chlorocarbosilanes) are not useful without modification because of the rapid hydrolysis of Si—Cl bonds, forming HC1 and an insoluble crosslinked polymer network. However, nucleophilic substitution of these Si—Cl bonds with various reagents produces materials widi a broad range of properties that are determined by the nature of the nucleophile used.47 Poly(chlorocarbosilanes) can be easily synthesized by ADMET (Fig. 8.18) without any detrimental side reactions, since the Si—Cl bond is inert to both catalysts 12 and 14. Early studies produced a polymer with Mn = 3000.14f... 

The most common behavior, especially for substrates with Si—Cl bonds, is the extensive isomerization of excess of olefin during rapid hydrosilylation. 

C09-0030. What factor accounts for each of the following differences in bond length (a) The bond is longer than the CDC bond, (b) The C—Cl bond is shorter than the Si—Cl bond, (c) The C—C bond is longer than the O—O bond. 

When starting (chloromethyl)chlorosilane contained more than one Si-Cl bond, lower yields of the 1,3-disilacyclobutane were obtained due to side reactions resulting from the availability of more Si-Cl functions (in the case of CH3Si(CH2Cl)Cl2, 2 was produced in addition to cyclo-[CH3(Cl)SiCH2]2) and to formation of higher yields of polysilmethylene [13, 14]. 

Palladium dimethylsilanedithiolato complex is a precursor for Ti—Pd and Ti—Pd2 heterometal-lic complexes.311 The bis-silyl sulfides (R3Si)2S have been widely used to prepare a variety of metal sulfide clusters, because these reagents exploit the strength of the Si—O and Si—Cl bond to... 

The Si-Cl bonds will react in ways that are typical of covalent bonds between halogens and nonmetals. One such reaction is... 

The method of competitive reactions was used (38) to measure the relative rates of addition of Et3 ClnSiH (n = 0-3) to 1-heptene with Co2(CO)8 and RhCl(PPh3)3 as catalysts. With the rhodium catalyst at 80°C no hydrosilation took place at 120°C only that silane with a greater number of Si—Cl bonds yielded products. 

The germylene 107 undergoes an oxidative insertion into an Si-Cl bond of SiCU (Equation (255)), and the reaction pathway of this process has been proposed (Equation (256)).320... 

Stannylsilanes have also been made by the insertion of a diarylstannylene into an Si-Cl bond (Equation (163)). 

The X-ray structure of 83 was in accord with the prediction of Scheme 4 in that the Si-Cl bond lies in the niobocene bisecting plane trans to the hydride and is elongated compared with classical complexes of the type [M(SiR2Cl)L ]. There was, however, no good reference system that would allow for the comparison of the Nb-Si bond lengths. The metal-silyl bond lengths are strongly affected by Bent s... 

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