Silicon derivatives

The Peterson reaction has two more advantages over the Wittig reaction 1. it is sometimes less vulnerable to sterical hindrance, and 2. groups, which are susceptible to nucleophilic substitution, are not attacked by silylated carbanions. The introduction of a methylene group into a sterically hindered ketone (R.K. Boeckman, Jr., 1973) and the syntheses of olefins with sulfur, selenium, silicon, or tin substituents (D. Seebach, 1973 B.T. Grdbel, 1974, 1977) illustrate useful applications. The reaction is, however, more limited and time consuming than the Wittig reaction, since metallated silicon derivatives are difficult to synthesize and their reactions are rarely stereoselective (T.H. Chan, 1974 ... 

Kira reported the synthesis of a derivative of spiro[2.2]pentasiladiene 101 [5, 16], The spiropentadisilene derivative is stable with a melting point of 216-218 °C, whereas spiropentadiene 98 decomposes even below -100°C [81], The carbon congeners are more strained with introdnction of the double bond(s), while the silicon derivatives possess almost the same SE (Scheme 34) [5],... 

Marciniec B, Pretrasznk C (2004) Synthesis of Silicon Derivatives with Rntheninm Catalysts. 11 197-248... 

Synopsis of dangerous reactions of sulphur, phosphorus and silicon derivatives... 

Of the group 14 elements (Si, Ge, Sn and Pb), only tin is known to form a variety of poly(pyrazoIyl)borato alkyl derivatives. For example, the reactions between K[pzTp] and the silicon derivatives Me SiCl4 (n = 1-3) have not given tractable products (115). Similarly, the reaction between K[pzTp] and Me2GeCl2 gives a complex that has been spectroscopically characterized as [pzTp]2GeMe2, but which readily decomposes. 

Table 1 Molecular parameters of the diatomic oxides and sulfides of carbon and silicon derived experimentally (force constant f and bond energy BE) and theoretically (bond distance d, charge Q, and Shared Electron Number SEN).

Table 8 Comparison of 11B and 29Si NMR constants for boron and silicon derivatives with and without Si-H-B interraction...

The two acetylenic functions in the silicon or tin derivative make possible a competition between 1 1 and 2 1 reactions (Scheme 39, pathway b), and the product ratio depends significantly on the reaction conditions. For silicon derivatives an excess of 1-boraadamantane in the reaction mixture (acetylenic component added to 1-boraadamantane) leads to the octacyclic compounds 88 (up to 60%), while when the much more reactive 1-alkynyltin analogues are used, a second intramolecular 1,1-organoboration often takes place <2001CEJ775>. The stmcture of 88c (M = Sn, R = Me, R1 = SiMe3) was confirmed by X-ray analysis <2001CEJ775>. 

The most widely applied commercial nano filtration membrane is the MPF series of Koch Int.[19] (Figure 4.9). The series contains polymeric silicon-derived membranes in the MWCO range of 400-700 Da. [20] The membranes are supplied in a 50% ethanol / water mixture, and should under no circumstances be allowed to dry out. Before use, the membranes must be conditioned with the solvent of choice. 

STARMEM240 400 MET polyimide silicon derived Tol, Xyl, EtOAc, C6 common org solvents, limited 60... 

Mack, S. Meitl, M. A. Baca, A. J. Zhu, Z.-T. Rogers, J. A. 2006. Mechanically hexible thin-hlm transistors that use ultrathin ribbons of silicon derived from bulk wafers. Appl. Phys. Lett. 88 213101. 

A pjr-djr effect was found also in the silicon derivative in the series p-CICgEEMMes (M = C, Si, Ge, Sn)74. In this case the hyperconjugation minimizes the difference in orbital energy 712-713, where 713 is the phenyl orbital affected by the conjugation, which is stabilizing for the chlorine 3p orbitals, destabilizing for the M empty d orbitals. 

A recent review covers the redox chemistry of monomeric and oligomeric phthalocyanines in the form of monomers and stacks174. Of the group 14 elements, the electrochemical redox data described concerns mostly silicon derivatives and one germanium compound, m -oxobis(tetra-t -butyl) phthalocyanatogermanium175. 

In silicon derivatives, X-ray studies of compound 27 were consistent with a covalently bonded trigonal bipyramidal molecule <2000CC565>. In addition, nucleophilic substitution at silicon for similar compounds was modeled either by NMR or X-ray techniques and both methods correlate in the calculation of % Si-O bond formation <2003JOM66, 2003JOM154>. 

Clusters of the elements aluminum to thallium containing only one or two carbon atoms and strong direct element-element interactions, similar to boron rich car-baboranes, have not yet been synthesized, and also the corresponding silicon derivatives are relatively rare. To the best of our knowledge only one aluminum-silicon and one gallium-silicon cluster (1 and 2) has been reported in the literature. The reaction of metastable aluminum(I) chloride with decamethylsilicocene or with a mixture of SiCl4 and (AlCp )4, respectively, afforded black crystals of... 

Silicon derivatives of these simple amines have also been studied using /-irradiation in CFCI3 solution at 77 K. The radical cations 7 and 8 are formed in each of the cases. The EPR study showed that the singly filled MO of the radical cation was delocalized and extended into the silyl groups. The hydrazine derivative 9 also affords a radical cation... 

Iridium siloxide complexes show a similar activity. Catalytic tests performed in the presence of [ Ir( 4-OSiMe3)(cod) 2], with the use of trimethylvinylsilane and dimethylphenylsilane as reactants [59], gave the same type of silicon derivatives as those obtained by Murai and coworkers [58], but the siloxide iridium precursor used appeared to be more efficient under milder conditions. When the [Ir(cod)(PCy3)(OSiMe3)] was used rather than the binuclear iridium siloxide complex, Z-Me3SiCH2CH=CHOSiMe2Ph was obtained exclusively [59],... 

Other silicon derivatives containing Si—X—C bonds (where X is O and/or N) can be successfully prepared by using iridium-catalyzed reachons such as the asymmetric hydrosilylation of ketones and amines, the silylcarbonylation of alkenes, and the alcoholysis of Si—H bonds. Indeed, oxygenation of the latter bond to silanol also proceeds smoothly in the presence of iridium compounds. 

Mardniec, B. and Pietraszuk, C. (2004) Synthesis of silicon derivatives with mthenium catalysts, in Topics in Organometallic Chemistry, Vol. 11 (ed. 

Coupling constant data (Hz) for silicon derivatives of triethylphosphines... 

The a-elimination process is a very fast and effective reaction of trifluoromethyl carbanions (Figure 1.9)." Consequently, the corresponding organometallic species (Li, Mg) cannot be used in organic synthesis. When the carbon-metal bond is close to a covalent bond, the anionic species is more stable, but has almost no reactivity toward electrophiles. Zinc, and especially silicon, derivatives constitute the best compromises." When the fluoroalkyl chain is longer, organometallics are more stable and can be used in synthesis (Figure 1.10)." ... 

The diphenyl derivative is more stable than the radical anion of its carbon derivative, 9,9-diphenylfluorene, but, after extended periods of reduction, the spectrum of the biphenyl radical anion begins to grow in intensity. The 5,5-dimethyl derivative appears to be stable under these conditions. The enhanced stability of the silicon derivative might be due to stabilization of the carbon-silicon bonds by delocalization of charge into available d-orbitals 81). Methyl proton hyperfine splitting observed for the anion radicals of the 5,5-dimethyl- and 5,5-diethyldibenzosilole has been cited as evidence for d-7r interaction (56). 

The mechanism of the photochemical degradation of catenated silicon derivatives has received considerable attention (25). Substituted cyclic derivatives photochemically extrude a silylene fragment which can be intercepted by appropriate trapping reagents (e.g., trialkylsilanes or 2,3-dimethyl butadiene). This extrusion results in the formation of the corresponding ring contracted cyclopolysilane. The process continues upon additional irradiation until a cyclotetrasilane results which then undergoes... 

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