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  • 1
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 921-926 
    ISSN: 1434-1948
    Schlagwort(e): Aluminium ; Chelates ; Lewis acids ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Sodium nitrite (NaNO2) dissolves readily in THF, when the methylene-bridged dialuminium compound R2Al-CH2-AlR2 [R = CH(SiMe3)2] 1 with two coordinatively unsaturated aluminium atoms is added. Compound 1 reacts as a chelating Lewis acid, and, as shown by a crystal structure deter-mination of the [Na([18]crown-6)(Et2O)]+ derivative 5c, a compound (5) is formed, in which one oxygen atom and the nitrogen atom of the nitrite ion are each coordinated by one aluminium atom to form a five-membered Al2CNO hetero-cycle. The second oxygen atom of the nitrite anion is not affected. Similarly, lithium nitrate (LiNO3) reacts with 1 to yield a THF soluble product (6a). Single crystals were obtain-ed of the [Li(N,N′,N′′-trimethyltriazinane)2]+ derivative 6c, whose structure shows each aluminium atom to be coordinated by one oxygen atom of the nitrate ion to give a six-membered Al2CNO2 heterocycle.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 1434-1948
    Schlagwort(e): Aluminium ; Gallium ; Diazo compounds ; Dimerization ; Coordination modes ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Lithium trimethylsilyldiazomethanide Li(SiMe3)CN2 reacted with the dialkylaluminium or -gallium halides R2AlCl and R2GaBr [R = CH(SiMe3)2] by the elimination of lithium halide and the formation of the corresponding aluminium or gallium diazo compounds. As shown by a crystal structure determination, the gallium derivative 1 adopts the nitrile imine structure, in which the gallium atom is coordinated by the terminal nitrogen atom of the diazo group. The N-N-C-Si moiety is almost ideally linear with N-N and C-N bond lengths of 125.5 and 115.9 pm on average. In contrast, the diazomethane structure was formed with dialkylaluminium chloride, and the aluminium atom in 2 is attached to the carbon atom of diazomethane. The almost linear N-N-C group (174.1°) has N-N and N-C distances of 120.0 and 126.4 pm, respectively, inverse to that of the gallium derivative. The bonding situations can best be described by the resonance structures R-C≡N+-N--GaR2 for 1 and R2Al-(R)C=N+=N- for 2. The nitrile imine isomer of the aluminium compound could be detected by NMR spectroscopy as a by-product. Both compounds gave dimers in the solid state, a Ga2N2 four-membered heterocycle was formed of 1, while an eight-membered Al2C2N4 heterocycle resulted with 2.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 0009-2940
    Schlagwort(e): Silicon ; Germanium ; Tin ; Carbene homologues ; Digermene ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The reaction of the diaminosilylene :Si(tBuNCH2CH2NtBu) (5) with the diaminogermylene :Ge(tBuNCH2CH2NtBu) is thought to proceed via a germasilene → silylgermylene rearrangement and dimerisation to furnish the (Z)-1,2-diamino-1,2-disilyldigermene (Z)-9. The X-ray structure analysis of (Z)-9 reveals a long Ge—Ge bond length of 245 pm and a large trans-bent angle of 42°. Air-oxidation of (Z)-9 takes place with retention of configuration at the germanium atoms to provide the corresponding substituted (Z)-2,4-digerma-1,3-dioxetane (Z)-10. Treatment of 5 with the stannylene :Sn[N(SiMe3)2)2 gives, as a final product, the hydridodisilylstannane 12. The structures of (Z)-10 and 12 were also determined by X-ray crystallography.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 0009-2940
    Schlagwort(e): Germanium ; Digermenes ; Tin ; Germylenes ; Stannylenes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Treatment of GeCl2 · dioxane with the Grignard reagent RMgBr (R=2-tBu-4,5,6-Me3C6H) furnishes the tetraaryldigermene R2Ge=GeR2 (8). X-ray structure-analysis of 8 reveals a short Ge=Ge double bond, a nearly planar environment of both germanium atoms and extremely widened C—Ge—C angles of 128°. In solution, 8 dissociates into two germylene molecules R2Ge, which can be trapped with oxygen or by [4+1] cycloaddition reactions with 1,4-dihetero-1,3-dienes. A similar cycloadduct of a stannylene wa obtained by thermolysis of (R′2Sn)3 (R′=2,4,6-iPr3C6H2), in the presence of a 1,4-diazabutadiene and characterized by an X-ray structure-analysis.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    ISSN: 0044-2313
    Schlagwort(e): Aluminium ; indium ; Al—Al bond ; In—In bond ; benzoato bridges ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: The Reactions of R2Al—AlR2 and R2In—InR2 with Benzoic Acid - Synthesis and Crystal Structure of R2Al(μ-H)(μ-O2C—C6H5)AlR2 and RIn(μ-O2C—C6H5)4InR [R = CH(SiMe3)2]Tetrakis[bis(trimethylsilyl)methyl]dialane(4) 1 reacts with benzoic acid by the oxidative cleavage of the Al—Al bond: The Al atoms are inserted into the O—H bond of the acid and the proton is reduced to a hydride anion. As shown by a crystal structure determination, the product 4 shown an unprecedented structure with both dialkylaluminium fragments unsymmetrically bridged by the hydrogen atom and a benzoato group. 4 can be described as a model compound for the first step of the hydrolysis of compounds with low-valent Al atoms as well as elemental aluminium itself. The diindane(4) analogue of 1 (2) and benzoic acid yield, however, elemental indium and mixed alkyl benzoato indium derivatives, from which bis(trimethylsilyl)methyldi(benzoato)indium 9 has been characterized by a crystal structure determination. 9 consists of a dimer with a remarkable cage structure, in which both monoalkylindium groups are interconnected by four benzoato-O,O′ bridges.
    Notizen: Tetrakis[bis(trimethylsilyl)methyl]dialan(4) 1 reagiert mit Benzoesäure unter oxidativer Öffnung der Al—Al-Bindung, wobei sich formal die Al-Atome in die O—H-Bindung der Säure einschieben und das Proton zu einem Hydridion reduzieren. Die beiden Dialkylaluminium-Fragmente des daraus erhaltenen Produkts 4 werden, wie durch Kristallstrukturbestimmung gezeigt wird, in bisher unbekannter Weise durch das Wasserstoffatom und eine Benzoatogruppe unsymmetrisch miteinander verbrückt. 4 läßt sich als Modellverbindung für die erste Stufe der Hydrolyse von Derivaten mit niederwertigen Al-Atomen und elementarem Aluminium beschreiben. Das zu 1 analoge Diindan(4) 2 ergibt dagegen mit Benzoesäuren unter Abscheidung von elementarem Indium gemischte Alkyl-benzoatoindium-Verbindungen. Bis(trimethylsilyl)methyl-di(benzoato)indium 9 wird kristallstrukturanalytisch untersucht; es liegt als Dimeres mit einer Käfigstruktur vor, in der zwei Monoalkylindium-Reste über vier Benzoato-O,O′-Brücken miteinander verbunden werden.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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