- Reaction of the (dichloromethyl)oligosilanes R(Me3Si)2Si - CHCl2 (R = Me, Ph, Me3Si) with organolithium reagents and the synthesis of novel kinetically stabilized silenes
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The dichloromethyloligosilanes R1(Me3Si)2Si - CHCl2 (1a,b) (1a: R1 = Me; 1b: R1 = Ph), prepared by treatment of methylbis(trimethylsilyl)silane or phenylbis(trimethylsilyl)silane respective
- Schmohl, Kathleen,Reinke, Helmut,Oehme, Hartmut
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p. 481 - 489
(2007/10/03)
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- Dimere der Ethene Me2E=C(SiMe3)2 (E=Si, Ge, Sn): Auf welchem Wege entstehen sie aus Me2EX-CM(SiMe3)2? Wie sind sie strukturiert?
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Alkali metal organyls or silyls MR (e.g. LiMe, LinBu, LitBu, LiPh, LiCH(SiMe3)2, LiC(SiMe3)3, NaSitBu3) convert equimolar amounts of bromomethanes Me2EX-CBr(SiMe3)2 with E=Si, Ge, Sn and electronegative substituents X (e.g. F, Br, OPh) in organic solvents (e.g. pentane, diethyl ether, tetrahydrofuran) (i) by a very fast Br/M exchange into the 'metalation products' Me2EX-CM(SiMe3)2, which thermolyze under formation of 'cyclobutanes' [-Me2E-C(SiMe3)2-]2, and (ii) to a lesser extent by X/R exchange into 'substitution products' Me2ER-CBr(SiMe3)2. As shown by trapping experiments, the unsaturated compounds Me2E=C(SiMe3)2 play the role of short-lived intermediates in both reactions. They are formed from Me2EX-CM(SiMe3)2 by MX elimination and add the present alkalimetal compounds Me2EX-CM(SiMe3)2≡MR′ or MR, respectively. The products Me2ER′-CM(SiMe3)2 with R′=C(EXMe2)(SiMe3)2, obtained in this way, eliminate MX under formation of the mentioned 'cyclobutanes'. On the other hand, the compounds Me2ER-CM(SiMe3)2 convert unreacted Me2EX-CBr(SiMe3)2 in Me2EX-CM(SiMe3)2 under formation of Me2ER-CBr(SiMe3)2. Relative rates of both the metalation reactions and the salt eliminations are determined. X-ray structure analyses of [-Me2E-C(SiMe3)2-]2 (E=Si, Ge, Sn) prove their 1,3-dielementacyclobutane structure with planar four-membered ECEC rings.
- Wiberg,Passler,Wagner,Polborn
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p. 292 - 303
(2007/10/03)
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- Reaction of (Me3Si)2C(SiMe2Ph)(SiEt2I) with AgBF4. 1,3-Migration of the Phenyl Group
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The reaction of (Me3Si)2C(SiMe2Ph)(SiEt2I) with AgBF4 in Et2O has been shown to give a ca. 2:3 ratio of the unrearranged (Me3Si)2C(SiMe2Ph)(SiEt2F) and the rearranged (Me3Si)2C(SiEt2Ph)(SiMe2F).The reaction is thought to proceed via a cation, II, in which
- Eaborn, Colin,Lickiss, Paul D.,Najim, Sabah T.,Stanczyk, Wlodzimierz A.
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- 1,3-Migration of a Phenyl Group via a Silicocation
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The reaction of (Me3Si)2C(SiMe2Ph)(SiEt2I) with AgBF4 in Et2O has been shown to give a ca. 2:3 ratio of the unrearranged (Me3Si)2C(SiMe2Ph)(SiEt2F) and the rearranged (Me3Si)2C(SiMe2F)(SiEt2Ph); the reaction is thought to proceed via a Ph-bridged cation (
- Eaborn, Colin,Lickiss, Paul D.,Najim, Sabah T.,Stanczyk, Wlodzimierz A.
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p. 1461 - 1462
(2007/10/02)
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- On the Way to Silaethene Me2Si=C(SiMe3)2: Trisilylated Methanes (Me3Si)2(Me2XSi)CY (X=e. g. Hal, RO, RS; Y e. g. Br, Li)
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Bromotrisilylmethanes (Me3Si)2(Me2XSi)CBr (1 - 15) are formed as a result of the reaction of (Me3Si)2(Me2PhSi)CBr (16) with iodine monochloride, bromine and iodine (X = Cl, Br, I) respectively, and also through the reaction of (Me3Si)2(Me2BrSi)CBr (1) with AgX (X = F, p-TolSO2, p-TolSO3, MesSO3, Ph2PO2, Ph2PO3, Ph2PO4) or MX (M = H, Li, Na; X = HO, RO, RS, Bu, Ph).Butyl- as well as phenyllithium convert bromotrisilylmethanes 1 - 16 at low temperatures into lithium derivatives (Me3Si)2(Me2XSi)CLi (1a - 16a).These are in some cases (X = R, RO) thermostable, whereas, in other cases they decompose more or less readily under LiX elimination and lead (in many cases via silaethene Me2Si=C(SiMe3)2) to the disilacyclobutane derivative 2 (17).Acids HZ (e. g.HCl, HOMe, Me3CBr) protonate the lithium compounds into (Me3Si)2(Me2XSi)CH as well as (Me3Si)2(Me2ZSi)CH.Butyl bromide converts the more stable lithium compounds (Me3Si)2(Me2XSi)CLi (X = R, RO, F, Ph2POn) into butyl derivatives (Me3Si)2(Me2XSi)CBu.
- Wiberg, Nils,Preiner, Gerhard,Schieda, Oswald
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p. 2087 - 2103
(2007/10/02)
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