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  • 1
    Electronic Resource
    Electronic Resource
    Controlled Conversion of the Transient 2-Mesityl-1,1-bis(trimethylsilyl)silene into a Tetrahydro-2,3-disilanaphthalene, a 1,2-Disilacyclobutane, or a 1,3-Disilacyclobutane (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1083-1088 
    Details
    ISSN: 0009-2940
    Keywords: Silenes ; Silene dimerization ; 1,2-Disilacyclobutanes ; 1,3-Disilacyclobutanes ; 2,3-Disilanaphthalene, tetrahydro- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mesityl[tris(trimethylsilyl)silyl]methanol (1) reacts with strong bases with elimination of trimethylsilanolate according to a Peterson-type mechanism, the outcome of the reaction being dependent on solvent, temperature, and nature of the organometallic base applied. Thus, 1 was converted by treatment with MeLi in ether at -78°C to (E)-1,2,3,8a-tetra -hydro-1-mesityl-5,7,8a-trimethyl-2,2,3,3-tetrakis (trimethylsi-lyl)-2,3-disilanaphthalene (3), formally a [2 + 4] cyclodimer of the transient silene (Me3Si)2Si=CHMes (2). The reaction of 1 with PhMgBr in THF after some days resulted in the formation of (Z)-3,4-dimesityl-1,1,2,2-tetrakis(trimethylsilyl) -1,2-disilacyclobutane (6) as the main product besides small quantities of 3, the polysilane (Me3SiSi(SiMe3)2CH2Mes (10), and the alkoxysilane (Me3Si)3SiCH(Mes)OSi(Si-Me3)2CH2Mes (7). Compound 6, the formal [2 + 2] cycloadduct of 2, can also be obtained by thermal treatment of 3 and is considered to be the thermodynamically more stable silene dimer whereas 3 is the kinetically preferred product. At high LiBr concentrations in the reaction mixture 1 was converted by PhMgBr in THF to (E)-2,4-dimesityl-1,1,3,3-tetrakis(tri- methylsilyl)-1,3-disilacyclobutane (13) besides 6 and [bis(tri-methylsilyl)silyl]mesityl(trimethylsiloxy)methane (11). The unforeseen formation of 13 is discussed as proceeding via the silene-lithium bromide adduct (Me3Si)2Si(Br)CH(Li)Mes (12). In the absence of LiBr 1 was converted by MeLi in THF at -78°C to 11 and the trisilane (Me3Si)2Si(Me)CH2Mes (4b). Probable pathways of the formation of all new compounds are discussed. For 6 and 13 the results of the X-ray structural analyses are given.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951281105
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  • 2
    Electronic Resource
    Electronic Resource
    Geminal di(hypersilyl) Compounds  -  the Synthesis and Structure of Bis[tris(trimethylsilyl)silyl]methanol (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1709-1714 
    Details
    ISSN: 0009-2940
    Keywords: Silicon ; Strained molecules ; Silanes, sterically congested ; Tris(trimethylsilyl) silanes ; Silenes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(trimethylsilyl)silyllithium (1) reacts with methyl formate in diethyl ether (molar ratio 2:1) to give 1,2-di(hypersilyl)- ethylene 13. The formation of 13 proceeds through the intermediates formyl tris(trimethylsilyl)silane (4) and lithium bis-[tris(trimethylsilyl)silyl]methoxide (5). In diethyl ether, the alkoxide 5 spontaneously eliminates lithium trimethylsilanolate thereby generating 1,1-bis(trimethylsilyl)-2-[tris(trimethylsilyl)silyl]silene (9), which undergoes a formal [2+2] cycloaddition with the carbonyl compound 4 to afford 13. This was verified by crossover experiments. In Pentane, the alkoxide 5 is moderately stable. Thus, the intermediate 5, prepared by reaction fo 1 with tert-butyl formate in pentane. was protonated with water to give the di(hypersilyl)methanol 6 in good yield. The structure of 6 in good yield. The structure of 6 was elucidated by an X-ray crystal structure analysis, which expectedly revealed tremendous distortions of the molecular skeleton. Thus, the spatial demand of the two extended hemispherical (Me3Si)3Si groups forces a widening of the Si-C-Si angle at the central sp3 carbon atom to a value of 135.5°.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301123
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of Transient Silenes by a Modified Peterson Reaction (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 143-149 
    Details
    ISSN: 0009-2940
    Keywords: Silenes ; Silene dimerization ; 1,2-Disilacyclobutanes ; 2,3-Disilanaphthalene, tetrahydro- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(trimethylsilyl)silylmagnesium bromide, obtained in situ from tris(trimethylsilyl)silyllithium and magnesium bromide, reacts with acetone, pivalaldehyde, or 2,4,6-trimethylbenzaldehyde to give the (1-hydroxyalkyl)tris(trimethylsilyl)silanes (Me3Si)3SiC(OH)Me2 (1a), (Me3Si)3CH(OH)tBu (1b), and (Me3Si)3SiC(OH)Mes (1c), resp. After deprotonation with methyllithium in ether at -78°C 1a-c eliminate trimethylsilanolate according to a modified Peterson mechanism to form transient silenes (Me3Si)2Si=CR1R2 (6a: R1 = R2 = Me; 6b: R1 = H, R2 = tBu; 6c: R1 = H, R2 = Mes). In the absence of trapping agents these silenes dimerize, 6a leading to the linear dimer 1-isopropenyl-2-isopropyl-1,1,2,2-tetrakis(trimethylsilyl)disilane (7) and 6b giving the head-to-head cyclodimerization product (E)-3,4-di-tert-butyl-1,1,2,2-tetrakis(trimethylsilyl)-1,2-disilacyclobutane (8), whereas 6c in a very unusual cyclodimerization step affords (E)-1,2,3,8a-tetrahydro-1-mesityl-5,7,8a-trimethyl-2,2,3,3-tetrakis(trimethylsilyl)-2,3-disilanaphthalene (9). Compound 9 is the result of an unexpected [2 + 4] reaction, in which the silene formally acts as the monoene and - involving the aromatic substituent - simultaneously also as the diene. The reaction of 1a-c with methyllithium in THF at low temperature initiates 1,3-Si,O-trimethylsilyl migrations leading to (trimethylsiloxy)-[bis(trimethylsilyl)silyl]alkanes (Me3Si)2SiH-CR1R2OSiMe3 3a-c. Reaction of 1a-c with an excess of methyllithium, tert-butyllithium, or phenyllithium, leads to trisilanes (Me3Si)2-SiR3-CHR1R2 11a-e, formed by the addition of the organolithium reagent to the Si=C bond of the transient silences 6a-c. Deprotonation of 1b and 1c in the presence of 2,3-dimethyl-1,3-butadiene gives the [2 + 4] cycloadducts 6-tert-butyl-3,4-dimethyl-1,1-bis(trimethylsilyl)-1-sila-3-cyclohexene (12a) and 6-mesityl-3,4-dimethyl-1,1-bis(trimethylsilyl)-l-sila-3-cyclohexene (12b). For 8 and 9 the results of the X-ray analyses are given.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280210
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  • 4
    Electronic Resource
    Electronic Resource
    2-(2,4-Di-tert-butylphenyl)-1,1-bis(trimethylsilyl)silene and 2-(2,4,6-Tri-tert-butylphenyl)-1,1-bis(trimethylsilyl)silene - Two New Sterically Protected but Still Unstable Silaethenes (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 15-20 
    Details
    ISSN: 0009-2940
    Keywords: Silenes ; Silene dimerization ; 1,2-Disilacyclobutanes ; 2,3-Disilanaphthalene, tetrahydro- ; 2-Silanaphthalene, tetrahydro- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (2,4-Di-tert-butylphenyl)tris(trimethylsilyl)silylmethanol (1a), prepared by the reaction of tris(trimethylsilyl)silylmagnesium bromide with 2,4-di-tert-butylbenzaldehyde, was deproto-nated by treatment with methyllithium in ether at -78°C to give the transient 2-(2,4-di-tert-butylphenyl)-1,1-bis(trimeth-ylsilyl)silene (3a), which dimerizes in a head-to-head fashion with the formation of (E)-/(Z)-3,4-bis(2,4-di-tert-butylphenyl)-1,1,2,2-tetrakis(trimethylsilyl)-1,2-disilacyclobutane (5). Besides 5 an unstable compound 4 was obtained, which was preliminarly assigned as 5,7-di-tert-butyl-1-(2,4-di-tert-bu-tylphenyl) -1,2,3,8a-tetrahydro-2,2,3,3-tetrakis(trimeth-ylsilyl)-1,2-disilanaphthalene (4), the formal [2 + 4] cyclodimer of 3a. Compound 4 gradually decomposes to give (E)-/(Z)-5, and is considered to be the kinetically preferred dimer of 3a, which is converted into the thermodynamically stable 5. 2,4,6-Tri-tert-butylbenzaldehyde reacts with tris(tri-methylsilyl)silyllithium resulting in the formation of 6,8-di-tert-butyl-1,2,3,4-tetrahydro-4,4-dimethyl-2,2- bis(trimethylsilyl)-2-silanaphthalene (6). Compound 6 is the product of the insertion of the Si=C bond into the C-H bond of an o-tert-butyl group of the intermediate 2-(2,4,6-tri-tert-butylphenyl)-1,1-bis(trimethylsilyl)silene (3b), which despite extreme steric shielding proved to be still unstable. For compounds (Z)-5 and 6 the results of the X-ray analyses are given.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290105
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and Structure of Methoxybis[tris(trimethylsilyl)silyl]methane - The First Geminal Di(hypersilyl) Compound with a Central Carbon Atom (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 841-844 
    Details
    ISSN: 0009-2940
    Keywords: Methane, methoxybis[tris(trimethylsilyl)silyl- ; Tris(trimethylsilyl)silyllithium ; Dichloromethyl methyl ether ; Polysilanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methoxy-bis[tris(trimethylsilyl)silyl]methane (4), the first compound bearing two hypersilyl groups at a carbon atom, was synthesized by the reaction of tris(trimethylsilyl)silyllithium with dichloromethyl methyl ether. As a byproduct of the reaction, 1,2-dimethoxy-1,2-bis[tris(trimethylsilyl)silyl]-ethane (5) could be identified. Possible pathways leading to 4 and 5 are discussed. The structure of 4, elucidated by an X-ray crystal structure analysis, is characterized by tremendous distortions of the molecular skeleton due to the spatial demand of the two extended hemispherical (Me3Si)3Si groups. For example, the central Si-C-Si angle is widened to 132.7°, the trimethylsilyl groups of the two hypersilyl substituents are pressed together to give an average Si-Si-Si angle of 105.6°, and the methoxy carbon atom and the nearest neighboring trimethylsilyl carbon atom approach to a distance of 3.25 Å, i.e. approx. 19% less than the sum of the van der Waals radii of two methyl groups.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290717
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  • 6
    Electronic Resource
    Electronic Resource
    The Acid-Induced Rearrangement of 1-Hydroxyalkyltris(trimethylsilyl)silanes (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 177-181 
    Details
    ISSN: 1434-1948
    Keywords: Silanes ; Rearrangements ; Polysilanes ; Hypersilylalcohols ; 1,2-Trimethylsilyl migration ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the presence of strong acids, such as HCl or H2SO4, 1-hydroxyalkyltris(trimethylsilyl)silanes (Me3Si)3Si-C(OH)R1R2 (1a-f) isomerize by 1,2-Me3Si/OH exchange to give the trimethylsilylmethylsilanols (Me3Si)2Si(OH)-C(SiMe3)R1R2 (4a-f) [R1,R2: a: Me, Me; b: H, 4-MeC6H4; c: H, 4-iPrC6H4; d: H, Mes; e: H, 2-Me2NC6H4; f: H, 2,4,6-(MeO)3C6H2]. A mechanism for the isomerization is proposed. In the case of the reaction of 1d with sulfuric acid, the silylsulfate (Me3Si)2Si(OSO3H)-C(SiMe3)HMes (5) was isolated. 5 is the intermediate in the H2SO4-catalyzed isomerization of 1d and was converted in situ with methanol, acetic anhydride, HF or HCl to give the respective methoxysilane 6, acetoxysilane 7, fluorosilane 8, or chlorosilane 9. Deprotonation of 4a, d, f with sodium hydride causes a further rearrangement, a 1,3-C,O-trimethylsilyl migration, to give the siloxanes (Me3Si)2(Me3SiO)Si-CHR1R2 (11a, d, f).
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    The Synthesis and Dimerization of Transient 1-Silabutadienes (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 801-806 
    Details
    ISSN: 0044-2313
    Keywords: Silabutadienes ; syntheses ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese und Dimerisierung instabiler 1-SilabutadieneDurch Umsetzung des Tris(trimethylsilyl)-silyllithiums (5) mit 3,3-Dimethylacrolein oder Zimtaldehyd werden 3-Methyl-1-tris(trimethylsilyl)silyl-2-butenol(1) (6) und (E)-3-Phenyl-1-tris(trimethylsilyl)silyl-2-propenol(1) (7) hergestellt, die sich als geeignete Precursoren zur Gewinnung der instabilen 1-Silabutadiene (Me3Si)2Si = CHCH = CR1R2 8 und 9 (8: R1 = R2 = Me; 9: R1 = H, R2 = Ph) nach dem Prinzip der modifizierten Peterson-Reaktion erwiesen. So eliminieren 6 und 7 nach Deprotonierung mit überschüssigem MeLi in Ether bei tiefer Temperatur Trimethylsilanolat und bilden 8 und 9, die durch das überschüssige Organolithium-Reagens durch nucleophile 1,2- und 1,4-Additionsreaktionen abgefangen werden. In Abwesenheit von Abfangreagenzien, z. B. dann, wenn 8 und 9 aus 6 und 7 durch stöchiometrische Mengen MeLi in Ether erzeugt werden, dimerisieren die freigesetzten 1-Silabutadiene im Sinne einer formalen [2 + 2]-Kopf-Kopf-Cycloaddition und man erhält die 1,2-Disilacyclobutane 17 und 18 neben Polymermaterial. Die Einwirkung von MeLi auf 6 in Tetrahydrofuran bewirkt eine 1,3-Si,O-Trimethylsilylwanderung unter Bildung des Alkoxysilans (Me3Si)2SiH—CH(OSiMe3)CH = CMe2 19.
    Notes: 3-Methyl-1-tris(trimethylsilyl)silyl-2-butenol(1) (6) and (E)-3-Phenyl-1-tris(trimethylsilyl)silyl-2-propenol(1) (7) were prepared by the reaction of tris(trimethylsilyl)silyllithium (5) with 3,3-dimethylacrolein and (E)-cinnamaldehyde, resp. The alcohols 6 and 7 proved to be suitable precursors for the generation of the transient 1-silabutadienes (Me3Si)2Si = CHCH = CR1R2 8 and 9 (8: R1 = R2 = Me; 9: R1 = H, R2 = Ph) following the principle of the modified Peterson reaction. Thus, 6 and 7 after deprotonation with excess MeLi in ether at low temperatures eliminated trimethylsilanolate and gave 8 and 9, which were trapped by the excess organolithium reagent undergoing nucleophilic 1,2- or 1,4-addition reactions. In the absence of scavengers, e.g. when 8 and 9 were generated by treatment of 6 and 7 with stoichiometric quantities of MeLi in ether, the 1-silabutadienes dimerize in a [2 + 2] head-to-head fashion to give the 1,2-disilacyclobutanes 17 and 18, resp., besides polymeric material. Treatment of the alcohol 6 with MeLi in tetrahydrofuran caused a 1,3-Si,O-trimethylsilyl shift affording the alkoxysilane (Me3Si)2SiH—CH(OSiMe3)CH = CMe2 19.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220509
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