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  • 1
    ISSN: 1434-4475
    Keywords: Keywords. Cyclosiloxanes; Functionalized cyclosiloxanes; Molecular alumosiloxanes; Host-guest chemistry in molecular alumosiloxanes.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  The synthesis of cyclic polysiloxanes of the general formula (OSiX 2) n with X=halogen, nitrogen, or oxygen centered ligand is achieved using a new strategy of assembling difunctional entities. The actual progress in this field is reviewed. Furthermore, polysiloxanes are described in which at distinct locations the silicon atoms are replaced by aluminum to which hydroxide groups are attached. The central molecule of interest has the formula [(Ph2Si)2O3Al(OH)]4, and its reactions with bases like diethylether, triethylamine, or pyridine are discussed following ideas of host-guest chemistry. Reaction of [(Ph2Si)2O3Al(OH)]4 with lithium organyls are also reviewed.
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  • 2
    ISSN: 1572-9753
    Keywords: dispersal ; species abundance ; xerothermic habitat ; Stenobothrus lineatus ; Stenobothrus stigmaticus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Nature of Science, Research, Systems of Higher Education, Museum Science
    Notes: Abstract Two congeneric species of grasshopper, Stenobothrus lineatus and S. stigmaticus, are compared in an analysis of genetic structure relative to their observed mobility, and to the spatial structure of their habitat networks. The species differ in their habitat requirements, the latter being rarer and more restricted to isolated patches. We tested for different patch connectivity between the two species in an analysis of genetic variance (based on allozymes) under the assumption that, besides isolation, rarity influences the genetic parameters. Between the species we found no differences in genetic structure as estimated by FST; i.e., no isolation effects and no apparent differences between the species in the potential to move between habitat fragments on either a local or regional scale were found. However, the amount of genetic variation in the more widely distributed and less xerothermic S. lineatus was significantly higher than in S. stigmaticus. Some consistency with observed philopatry within patches was found (FIS 〉 0), but we consider regular dispersal events of medium and especially long distance to cause the habitat linking. We conclude that the connectivity between occupied patches inferred by genetic analyses can seldom be derived from low observed life-time movements recorded by conventional marking studies. Consequences of applying observed relative to indirect dispersal estimates for the examination of grasshopper metapopulations are discussed.
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  • 3
    ISSN: 1573-4846
    Keywords: barium titanate ; barium zirconate ; sol-gel ; metal alkoxide ; single-source precursor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-gel synthesis of nano-sized BaTiO3, BaZrO3 and BaTi0.5Zr0.5O3 ceramics using alkoxide and semi-alkoxide routes has been investigated and the pervoskites obtained have been compared with respect to crystallisation temperature, crystallite size and compositional purity. Heterometal alkoxides containing two (for BaTiO3 and BaZrO3) and three (for BaTi0.5Zr0.5O3) different metals were used as single-source precursors in the alkoxide route while semi-alkoxide synthesis was performed by reacting barium hydroxide or acetate with Ti and/or Zr alkoxides. Semi-alkoxide synthesis also produces stoichiometric and phase-pure oxides, however, at temperatures higher than 1000°C. At temperatures below 1000°C, BaCO3 and small amounts of other undesired phases (e.g., BaTi2O4) were present in the oxides derived from semi-alkoxide synthesis. Thermal behaviour, studied by TGA/DTA measurements, shows that thermal decomposition occurs in three major steps and depends on the educt composition and the synthesis route. Among alkoxide derived powders, crystalline BaTi0.5Zr0.5O3 phase is formed at 400°C while complete crystallisation of BaMO3 ceramics occurs around 600°C. The cubic to tetragonal phase transition for BaTiO3 is clearly observed at relatively low-temperature of 800°C. The stoichiometry and phase homogeneity of the obtained powders were demonstrated by energy dispersive X-ray analysis and powder diffractometry. The averaged crystallite size of the obtained nano-ceramics was evaluated using the FormFit programme. SEM and TEM observations revealed a high microstructural uniformity.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 104 (1971), S. 3191-3203 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Derivatives of Hydrazine, 3 Preparation and Oxidation of Silylated, Germylated, and Stannylated Hydrazines and OrganylhydrazinesOxidation of silyl- or germyl-substituted (trimethylstannyl)-organylhydrazines [for example (Me3Sn)RN - N(EMe3)(SnMe3); R = Me, CMe3, Ph; E = Si, Ge] with p-benzoquinone (or, less advantageously, with oxygen) affords silyl- and germyl-substituted diimines R-N=N-EMe3 in high yields. Stannyl-substituted organyldiimines (E = Sn) could not be prepared in this way. Methods for the preparation of the substituted organylhydrazines used for the oxidation reactions are reported.
    Notes: Durch Oxydation silylierter bzw. germylierter Trimethylstannyl-organyl-hydrazine, z.B. des Typs (Me3Sn)RN - N(EMe3)(SnMe3) (R = Me, CMe3, Ph; E = Si, Ge), mit p-Benzochinon (bzw. weniger vorteilhaft mit Sauerstoff) entstehen in hohen Ausbeuten silylierte und germylierte Organyldiimine R - N=N - EMe3. Stannylierte Organyldiimine (E = Sn) können auf diesem Reaktionsweg nicht gewonnen werden. Über die Darstellung der für die Oxydation benötigten substituierten Organylhydrazine wird berichtet.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 104 (1971), S. 3176-3190 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Derivatives of Hydrazine, 2 Preparation and some Properties of Tetrasubstituted Hydrazines (Me3E)2N - N(EMe3)2 (E = C, Si, Ge, Sn)Reaction of hydrazine, N2H4, with chlorides Me3ECl (E = C, Si, Ge, Sn) or amines Me3SiNMe2 and reaction of hydrazides (Me3E)mN2HnLip (m+n+p = 4) with Me3ECl yield easily sublimable, high melting and melting and thermally stable hydrazines (Me3E′)(Me3E″)N - N(E‴Me3)-(E‴′Me3) with similar (E = E′ = E″ = E‴ = E‴′) and different ligands Me3E (for example: E′ = C, E″ = Si, E‴ = Ge, E‴′ = Sn). Only hydrazines with trimethylstannyl groups are easily solvolized and oxidized.
    Notes: Durch Reaktion von Hydrazin, N2H4, mit Chloriden Me3ECl (E = C, Si, Ge, Sn) sowie Aminen Me3SiNMe2 bzw. durch Reaktion von Hydraziden (Me3E)mN2HnLip (m+n+p = 4) mit Me3ECl konnten gleichartig substituierte (E = E′ = E″ = E‴ = E‴′) sowie gemischt substituierte Hydrazine (Me3E′)(Me3E″)N - N(E‴Me3) (E‴′Me3) (z. B. E′ = C, E″ = Si, E‴ = Ge, E‴′ = Sn) als leicht sublimierbare, hochschmelzende und thermisch sehr stabile Verbindungen gewonnen werden. Nur die trimethylstannylgruppen-haltigen Hydrazine solvolysieren leicht und werden von Oxydationsmitteln rasch angegriffen.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 111 (1978), S. 2536-2546 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclic Diazastannylenes, V. Synthesis and Structure of a New Cage Compound with a SiN2Sn2O SkeletonThe cage compound 1,5-di-tert-butyl-6,6-dimethyl-3-oxa-1,5-diazonia-6-sila-2λ2,4λ2-distannatotricyclo[2.2.0.02,5]hexane (5) originates as an SnCl2 adduct from controlled hydrolysis of a mixture of 1,3-di-tert-butyl-2,2-dimethyl-1,3,2,4λ2-diazasilastannetidine (1) and 1,3-di-tert-butyl-4,4-dichloro-2,2-dimethyl-1,3,2,4λ4-diazasilastannetidine (2). Crystal data and the molecular structure have been obtained by X-ray methods (table 1; R = 0.035). The structure is dominated by an SnCl2 band, to which the cage units are connected via the oxygen atom acting as an electron donor (Sn—O: 2.07 Å). The cage can be understood as a regular N2Sn2 tetrahedron (Sn—N: 2.31 Å) bridged by a dimethylsilyl group (Si—N: 1.76 Å) across the N—N edge and by an oxygen atom across the opposite Sn—Sn edge (Sn—O: 2.09 Å). An alternative description would be that of a twisted six-ring D bridged across the 1,4- and 2,5-positions. All tin atoms in the structure conform to the stannate(II) geometry.
    Notes: Die Käfigverbindung 1,5-Di-tert-butyl-6,6-dimethyl-3-oxa-1,5-diazonia-6-sila-2λ2,4λ2-distannatotricyclo[2.2.0.02,5]hexan (5) entsteht als SnCl2-Addukt bei vorsichtiger Hydrolyse eines Gemisches aus 1,3-Di-tert-butyl-2,2-dimethyl-1,3,2,4λ2-diazasilastannetidin (1) und 1,3-Di-tert-butyl-4,4-dichlor-2,2-dimethyl-1,3,2,4λ4-diazasilastannetidin (2). Die Kristalldaten sowie die Molekülstruktur wurden mit röntgenographischen Methoden erhalten (Tab. 1; R = 0.035). Die Struktur baut sich aus einem SnCl2-Band auf, an das die Käfigmoleküle über den Sauerstoff als Elektronendonor gebunden sind (Sn—O: 2.07 Å). Der Käfig kann als N2Sn2-Tetraeder beschrieben werden (Sn—N: 2.31 Å), dessen gegenüberliegende N—N- und Sn—Sn-Kanten jeweils mit Dimethylsilyl (Si-N: 1.76 Å) bzw. Sauerstoff (Sn—O: 2.09 Å) überbrückt sind. Eine alternative Beschreibung wäre ein Sechsring in der „twist“-Konformation D, der in 1,4- und 2,5-Position nochmals verbunden ist. Alle in der Struktur vorkommenden Zinnatome erreichen eine Stannat(II)-Geometrie.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 2141-2152 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclic Diazastannylenes, XIII. [SnN2(CH3)2]4 and [SnNCH(CH3)2]4, Molecules with Cubane-like Structures1,3-Di-tert-butyl-2,2-dimethyl-1,3,2,4λ2-diazasilastannetidine (1) reacts in benzene with N,N-dimethylhydrazine spontanously and with isopropylamine after warming shortly to yield N,N′-di-tert-butyl-Si,Si-dimethylsilazane (2) and the tetrameric molecules (SnN2Me2)4 (5) and (SnNCHMe2)4 (6). An X-ray structure determination (R = 0.026) proves 5 to be built of a very distorted Sn4N4-cube, the nitrogen atoms being attached to dimethylamino groups. In the crystal the molecules are linked together by Sn—Sn contacts (351 pm) forming a zick-zack band, which runs in the direction of the hexagonal axis. Typical Sn—N bond lengths are found to be 220.9 and 225.1 pm, while the mean N—N distance is 146.2 pm. When heated or by contact with oxygen the crystals of 5 decompose vehemently: the products are found to be β-tin, molecular nitrogen, and varying amounts of methane, ethane, and dimethylamine (by contact with oxygen small amounts of tin(II)-oxide are formed as well).
    Notes: 1,3-Di-tert-butyl-2,2-dimethyl-1,3,2,4λ2-diazasilastannetidin (1) reagiert in Benzol mit N,N-Dimethylhydrazin spontan und mit Isopropylamin nach kurzem Erwärmen zu N,N′-Di-tert-butyl-Si,Si-dimethylsilazan (2) und den Tetrameren (SnN2Me2)4 (5) und (SnNCHMe2)4 (6). Eine Röntgenstrukturbestimmung (R = 0.026) zeigt, daß 5 einen stark verzerrten Sn4N4-Kubus besitzt, an dessen Stickstoffatome Dimethylaminogruppen gebunden sind. Im Kristall sind die Moleküle über Sn—Sn-Kontakte (351 pm) zu einem Zickzack-Band verknüpft, das in Richtung der hexagonalen Achse verläuft. Typische Sn—N-Bindungslängen liegen bei 220.9 und 225.1 pm, während für N—N 146.2 pm ermittelt werden. Beim Erhitzen sowie bei Sauerstoffzufuhr zersetzen sich die Kristalle von 5 heftig: als Produkte erhält man β-Zinn, molekularen Stickstoff und in wechselnden Mengen Methan, Ethan und Dimethylamin (bei Sauerstoffeinwirkung auch geringe Mengen an Zinn(II)-oxid).
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1941-1944 
    ISSN: 0009-2940
    Keywords: Alkali alkoxystannates(IV) ; Mixed metal alkoxides ; Tin(IV), pentavalent ; Coordination polymers, helical ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation and Structure of Alkali Penta-tert-butoxystannates(IV)Potassium, rubidium, and caesium tert-butoxide react with tin tetra-tert-butoxide in toluene to form compounds MSn(OtBu)5 [M=K(2), Rb (3), Cs (4)] in contrast to lithium and sodium tert-butoxide. The compounds 2-4 are soluble in non-coordinating solvents and seem to be almost monomeric. 2 crystallizes as 2 · 1/2 toluene in the orthorhombic space group Fddd. The X-ray structure determination shows 2 to be coordinated as a helical polymer with the tin atom in the center of a trigonal bipyramid of tert-butoxide groups interlinked by two structurally different potassium atoms.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2625-2635 
    ISSN: 0009-2940
    Keywords: Amides, hetero metal ; Polycycles ; Metal clusters of thallium ; Metal nitrogen bonding ; Carbanion, stabilized by metal complexation ; Silane, tris(tert-butylamino) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homo and Hetero Metal Amides of Tris(tert-butylamino)methylsilane - Polycycles and Clusters with Li, Na, Mg, Al and TlThe hydrogen atoms attached to nitrogen in tris(tert-butyl-amino)methylsilane (1) can be substituted by metallic main-group elements in a quite general way. If 1 is treated with trimethylaluminium apart from the monosubstituted product MeSi(tBuNH)2(tBuNAlMe2) (2) the trisamide MeSi(tBuNAlMe2)3 (3) is obtained. In similar ways complete substitution of the amino hydrogen atoms in 1 yields the compounds MeSi[tBuNMgN(SiMe3)2]3 (6), [MeSi(tBuNLi)3]2 (10), and [MeSi(tBuNTl)3]2 (11), the later two being dimeric. If methyl-magnesium iodide is allowed to react with 1 the intermediate MeSi(tBuNMgI)3 (4) in some instances can be isolated as the THF adduct or may react with a further equivalent of the Grignard compound to generate the complex [MgI-(THF)5]+ [MeSi(tBuNMgI)3CH3 · THF]- (5). The aluminium compound 2 has been used to access to heterometallic amides combining aluminium and sodium as in MeSi(tBuNAlMe2)(tBuNNa)(tBuNH) (7) or magnesium and aluminium as in the dimeric compounds [MeSi(tBuNAlMe2)(tBuNH)(tBuNMgI)]2 (8) and [MeSi(tBuNAlMe2)(tBuNH)(tBuNMgMe)]2 (9). X-ray structure analyses reveal 3 (tricyclic SiN3Al3 skeleton with Al - N distances from 2.014 to 2.025 Å), 6 (tricyclic Si-N3Mg3 skeleton), and 7 [bicyclic SiN3AlNa skeleton with Na - N distances of 2.47(1) and 2.52(1) Å] to be monomeric even in the solid state. The compounds 8 and 9 (both pentacyclic with spiro magnesium atoms) form centrosymmetric dimers by Mg - I - Mg and Mg - (CH3) - Mg bridges, respectively. The dimers 10 and 11 are completely different in terms of chemical bonding: while in the lithium compound 10 a centrosymmetric polycycle is formed by principly ionic interactions of the lithium atoms with corresponding nitrogen atoms, the centrosymmetric dimer in 11 is held together by Tl - Tl bonds. The X-ray structure analysis of 5 reveals the anion containing a Mg-coordinated CH3-.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 347-355 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclic Diazastannylenes, XXIV. - The Reaction of (tert-Butylimino)stannylene with Hydrogen Chloride(tert-Butylimino)stannylene (1) reacts with hydrogen chloride to form [tBuN(H)-SnCl]2 (2a), tBuNH2 · SnCl2 (3), and tBuNH3⊕ SnCl3⊖ (4). As separation of the crystalline products is difficult, alternative syntheses for 2a, 3 and 4 are necessary. Me2Si[N(tBu)H][N(tBu)]SnX (6a: X = Cl, 6b: X = Br, 6c: X = I) is a substrate which may be treated with tert-butylamine to yield 2a (X = Cl) or 2b (X = Br) quantitatively. 3 and 4 are obtained from 2a by addition of HCl. 6a, b, and c show temperature dependance in the 1H-NMR spectra which is due to intramolecular ligand rearrangements. X-ray determinations reveal 6a to crystallize in an orthorhombic lattice (space group P212121), 3 in two different lattices (monoclinic, P21/c, and triclinic, P1), and 4 again in a triclinic lattice P1). 6a is a molecule with an intramolecular donor-acceptor bond [Sn-N = 2.347(6) Å], 3 adopts the same structure in the two modifications consistent with an adduct of SnCl2 and tBuNH2 [Sn-N = 2.334(4) Å (monoclinic) and 2.338(4) Å (triclinic)], and and 4 has to be formulated as an ion pair tBuNH3⊕ SnCl3⊖ connected by H-Cl bridges in the crystal [Sn-Cl = 2.542 (mean number), C-N = 1.515(6) Å].
    Notes: (tert-Butylimino)stannylen (1) reagiert mit Chlorwasserstoff zu [tBuN(H)-SnCl]2 (2a), tBuNH2 · SnCl2 (3) und tBuNH3⊕ SnCl3⊖ (4). Da die Trennung der kristallinen Produkte Schwierigkeiten macht, ist man auf Alternativsynthesen von 2a, 3 und 4 angewiesen. Me2Si[N(tBu)H][N(tBu)]SnX (6a: X = Cl, 6b: X = Br, 6c: X = I) stellt eine Ausgangsstufe dar, die mit tert-Butylamin zu 2a (X = Cl) und 2b (X = Br) quantitativ umgesetzt werden kann. 3 und 4 entstehen aus 2a u.a. durch HCl-Addition. 6a, b und c zeigen unterschiedliche 1H-NMR-Spektren in Abhängigkeit von der Temperatur, was auf eine intramolekulare Ligandenumordnung hinweist. Die Röntgenstrukturanalysen von 6a (orthorhombisch, Raumgruppe P112121), 3 (monoklin, P21/c, und triklin, P1) und 4 (triklin, P1) weisen 6a als Molekül mit einer intramolekularen Donor-Akzeptor-Bindung [Sn-N = 2.347(6) Å], 3 in beiden Modifikationen als Addukt von SnCl2 an tBuNH2 [Sn-N = 2.334(4) Å (monoklin) bzw. 2.338(4) Å (triklin)] und 4 als Ionenpaar tBuNH3⊕ SnCl3- mit H-Cl-Brücken im Kristall aus [Sn-Cl = 2.542 (Mittelwert), C-N = 1.515(6) Å].
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