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  • 1
    ISSN: 1434-4475
    Keywords: Keywords. Density functional study; Silicon compounds; Metal silyl complexes; Anionic metal complexes.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung.  Der Einfluß des Substitutionsmusters des Silylliganden wurde für Komplexe des Typs (CO)4Fe(H)SiR 3 und der korrespondierenden Anionen [(CO)4FeSiR 3]− durch eine Dichtefunktional-Studie untersucht. Schrittweise Substitution von R=H gegen R=Cl führt bei beiden Komplextypen zu einer Verkürzung der Fe-Si-Bindung. Der Substitutionseffekt ist bei den anionischen Komplexen viel größer, was durch die stärkere Rückbindung vom Metallzentrum zum SiR 3-Ligand erklärt wird. Die optimierten Strukturen der Komplexe stimmen gut mit experimentell ermittelten überein. Die Elektronendichteänderungen werden auch in den berechneten Schwingungsfrequenzen der CO-Liganden und den Protonenaffinitäten der anionischen Komplexe widergespiegelt. Zunehmender Elektronenabzug durch die Silylliganden verringert die Protonenaffinität.
    Notes: Summary.  The effect of the substitution pattern at the silyl ligand in complexes of the type (CO)4Fe(H)SiR 3 and the corresponding anions [(CO)4FeSiR 3]− was investigated by a density functional study. Upon successive substitution of R=H for R=Cl, a contraction of the Fe–Si bond takes place in both types of complexes. The effect of the substitution is much larger in the anionic complexes which is explained by a higher degree of back bonding from the metal center to the SiR 3 ligand. The optimized structures of the complexes are in good agreement with related experimental ones. The changes in electron density at the metal center are also reflected in calculated vibrational frequencies of the CO ligands and the proton affinities of the anionic complexes. An increasing electron withdrawal by the silyl ligand lowers the proton affinity.
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  • 2
    ISSN: 1434-4475
    Keywords: Keywords. Hypervalency; Tin compounds; X-Ray structure analysis.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung.  Es wurden neue Organozinnderivate ArNSn(X)RR′ (ArN=2-Me2NCH2C6H4; X=Cl, H, OMe; R,R′=Me, Ph) sowie ArNSnCl2Ph und (ArN)4Sn synthetisiert und hinsichtlich intramolekularer Sn*N-Wechselwirkungen untersucht. Die Bildung der Methoxyderivate ArNSn(OMe)RR′ durch Reaktion von ArNSn(H)RR′ mit Methanol wird mit zunehmender Substitution von Methyl- durch Phenylgruppen schwieriger. Die Molekülstrukturen von ArNSnClMe2, ArNSnCl2Ph und (ArN)4Sn wurden durch Röntgenbeugung bestimmt. ArNSnClMe2 und ArNSnCl2Ph sind trigonal-bipyramidal gebaut, wobei die Sn*N-Wechselwirkung bei ArNSnClMe2 stärker ist als bei ArNSnCl2Ph. Bei (ArN)4Sn findet man in Kristall zwei kristallographisch unterschiedliche Moleküle mit schwachen Sn*N-Wechselwirkungen beider Aminogruppen. Sie unterscheiden sich durch die relative Position der Aminogruppen.
    Notes: Summary.  New organotin derivatives ArNSn(X)RR′ (ArN=2-Me2NCH2C6H4; X= Cl, H, OMe; R, R′=Me, Ph) as well as ArNSnCl2Ph and (ArN)4Sn were prepared and investigated with regard to intramolecular Sn*N interaction. The formation of the methoxy derivatives ArNSn(OMe)RR′ by reaction of ArNSn(H)RR′ with methanol is rendered more difficult by successive replacement of the methyl substituents by phenyl groups. The molecular structures of ArNSnClMe2, ArNSnCl2Ph, and (ArN)4Sn were determined by X-ray diffraction. ArNSnClMe2 and ArNSnCl2Ph have a trigonal bipyramidal structure, the Sn*N interaction being stronger in ArNSnClMe2 than in ArNSnCl2Ph. There are two crystallographically different molecules in crystalline (ArN)4Sn with weak Sn*N interactions of both amino groups. They differ by the relative position of the amino groups.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 131 (2000), S. 813-818 
    ISSN: 1434-4475
    Keywords: Keywords. Silicon compounds; Nanostructures; Structure elucidation; Solid state reactions.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  Reaction of solid SiO with CuI, AgI, AgCl, or AgF results in the formation of the silicon tetrahalides SiX 4 and elemental silver or copper. The crystal structure of SiI4 was re-determined (Si-I 2.427(2) and 2.416(4) Å).
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 131 (2000), S. 931-936 
    ISSN: 1434-4475
    Keywords: Keywords. Glycolate; Manganese complexes; X-Ray structure determination; Jahn-Teller effect.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  The crystal structure of consists of individual layers in which the anionic complexes form strings of vertex-sharing octahedral units. These strings are interconnected by units to form layers via Na-Cl and Na-O interactions. An outstanding feature of the compound are the unusually strong Jahn-Teller elongated trans- octahedra.
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  • 5
    ISSN: 1434-4475
    Keywords: Keywords. Metal Silyl complexes; Oxidative addition; Hydride complexes.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung.  Photochemische Umsetzung von Cp′Mn(CO)3 mit HMe2Si-1,2-C6H4-SiMe2H und von Cp′Mn(CO)2PMe3 mit HMe2Si-X-SiMe2H (X=1,2-C6H4, C2H4,O) führt zur Bildung der oxidativen Additionsprodukte Cp′(CO)(L)Mn(H)SiMe2-X-SiMe2H. Außer bei der Kombination X= 1,2-C6H4 und L= PMe3 werden auch die zweikernigen Komplexe [Cp′(CO)(L)Mn(H)SiMe2]2 X gebildet.
    Notes: Summary.  The photochemical reaction of Cp′Mn(CO)3 with HMe2Si-1,2-C6H4-SiMe2H and of Cp′Mn(CO)2PMe3 with HMe2Si-X-SiMe2H (X=1,2-C6H4, C2H4, O) results in the formation of the oxidative addition products Cp′(CO)(L)Mn(H)SiMe2-X-SiMe2H. Except for the combination X= 1,2-C6H4 and L=PMe3, the binuclear complexes [Cp′(CO)(L)Mn(H)SiMe2]2 X are additionally formed.
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  • 6
    ISSN: 1434-4475
    Keywords: Keywords. Silyl complexes; Platinum complexes; Ligand exchange.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung.  Umsetzung von cis-(R 3P)2Pt(SiPhMe2)2 mit einem Überschuß an HSi(OMe)3, HSiPh3, HSi3Ph7, HPh2SiSiMe3 oder H2SiPh2 führt zum stufenweisen Austausch der Silylliganden. Der Austausch des ersten SiPhMe2-Liganden erfolgt rascher als der des zweiten. Die Austauschgeschwindigkeit hängt von der Art der Reste R′ in HSiR 3 ′ ab und sinkt in der Reihenfolge HSi(OMe)3≫ H2SiPh2〉HPh2SiSiMe3≫HSi3Ph7〉HSiPh3. Bei der Reaktion von (R 3P)2Pt(SiMe2Ph)2 mit einem Überschuß an HSi(OMe)3 wird der Austausch in Abhängigkeit vom R 3P-Liganden in der Reihenfolge PPh2Me〉PEt3〉PPhMe2 langsamer. Bei der Reaktion des Chelat-Komplexes (Ph3P)(Ph3Si)Pt(PPh2CH2CH2CH2SiMe2) mit HSi(OMe)3 oder H2SiPh2 wird nur Austausch des nichtchelatisierten Silylliganden beobachtet.
    Notes: Summary.  Reaction of cis-(R 3P)2Pt(SiPhMe2)2 with an excess of HSi(OMe)3, HSiPh3, HSi3Ph7, HPh2SiSiMe3, or H2SiPh2 results in a stepwise exchange of the silyl ligands. Exchange of the first SiPhMe2 ligand is faster than that of the second. The exchange rate depends on the nature of the groups R′ in HSiR 3 ′ and decreases in the order HSi(OMe)3≫H2SiPh2〉HPh2SiSiMe3≫HSi3Ph7〉 HSiPh3. The rate of the exchange reaction of (R 3P)2Pt(SiMe2Ph)2 with an excess of HSi(OMe)3 depends on the R 3P ligand and decreases in the order PPh2Me〉PEt3〉PPhMe2. When the chelated complex (Ph3P)(Ph3Si)Pt(PPh2CH2CH2SiMe2) is reacted with HSi(OMe)3 or H2SiPh2, only exchange of the non-chelated silyl ligand is observed.
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  • 7
    ISSN: 1573-4846
    Keywords: aerogels ; porous materials ; elasticity ; hydrophobicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Organically modified aerogels were prepared by NH4OH-catalyzed hydrolysis and condensation of RSi(OMe)3 (R = Me, Pr n , Ph, Bu i )/Si(OMe)4 or (MeO)3Si-Y-Si(OMe)3/Si(OMe)4 (Y = C2H4, p-C6H4, C6H12) mixtures, followed by supercritical drying of the alcogels with methanol. Starting from 1:4 mixtures of RSi(OMe)3 and Si(OMe)4, hydrophobic aerogels with nearly no residual Si-OH or Si-OMe groups were obtained. These aerogels were therefore insensitive towards moisture. Their elastic constant was distinctly lower than that of unmodified silica aerogels. Aerogels similarly prepared from 1:8 mixtures of (MeO)3Si-Y-Si(OMe)3 and Si(OMe)4 had a rather high concentration of residual Si-OMe groups, and therefore they were hydrophilic. Their elasticity was about the same as that of unmodified silica aerogels. The difference between the two types of aerogels suggests different microstructures, depending on the nature of the organic groups.
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  • 8
    ISSN: 1573-4846
    Keywords: precursor chemistry ; titanium alkoxides ; polymerizable ligands ; hybrid materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Modified transition metal alkoxides with polymerizable organic ligands were synthesized which are worthwhile precursors for the development of novel inorganic-organic materials. Titanium tetraisopropoxide was treated with isoeugenol (2-methoxy-4-propenylphenol), itaconic anhydride (methylene succinic anhydride), and 2-acrylamido-2-methyl-propanesulfonic acid, respectively. Isoeugenol forms a chelate complex with titanium via the phenolic OH group and the oxygen of the methoxy substituent. The reaction products of the cyclic itaconic anhydride with titanium alkoxide were two isomers due to different paths of ring opening; the reaction proceeded without the formation of an alcohol. 2-Acrylamido-2-methyl-propanesulfonic acid formed a link to titanium via the SO3 group, and after hydrolysis the sol consisted of rather small particles.
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  • 9
    ISSN: 1573-1111
    Keywords: MALDI-TOF-MS ; supramolecular chemistry ; metal coordination array ; characterization in the solid state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract MALDI-TOF mass spectrometry was used for the characterization of metallo-supramolecular coordination arrays with molecular weights between 500 and 4000 g/mol. The stepwise loss of the counterions was used as an additional fingerprint for the investigated species. The isotope pattern yielded further information, especially in combination with simulations.
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  • 10
    ISSN: 1573-1111
    Keywords: terpyridine ; metal complexes ; thermal stability ; thin film preparation ; supramolecular systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 5,5''-Dimethyl-2,2':6',2''-terpyridine complexes with various transition metal ions like Zn(II), Co(II), Mn(II) and Hg(II) were investigated concerning their thermal properties. A significant dependency of the thermal stability (5% weight loss) of the complexes depending on the kind of metal ion used could be observed ranging from 315 to 390 °C. Furthermore, self-assembled thin films of such metallo-supramolecular Hg(II) complexes were prepared and characterized by synchrotron based X-ray reflectivity and fluorescence techniques.
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