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  • 1995-1999  (2)
  • 1985-1989  (1)
  • Inorganic Chemistry  (3)
  • 1
    Digitale Medien
    Digitale Medien
    X-ray and Solution Structure of Inosine 5' -Monophosphate Coordinated to (Ethylenediamine)palladium(II).  - the Importance of Intramolecular Hydrogen Bonding (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1551-1555 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Antitumor agents ; Nucleotides ; Palladium ; Hydrogen bonds ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The compound [Pd(en)(5′-IMP-N7)2].11 H2O, where 5′-IMP = inosine 5′-monophosphate, crystallizes in the tetragonal space group P4322 with the unit cell parameters: a = b = 12.060(5) and c = 28.510(5) Å, V = 4147(3) Å3, Z = 4. A head-to-tail orientation with A configuration is observed for the nucleotides which are coordinated through the N(7) positions such that d[Pd-N(7)] = 2.053(8) Å. The sugar moieties exhibit anti orientations toward the purine bases while their pukkers adopt C(3)′-endo conformation. The overall conformation about the phosphate backbone is gauche+. Intramolecular hydrogen bonding is observed between the phosphates and the NH groups of the en ligand with a donor-acceptor distance of 2.88 Å. The coordination mode of the solid-state structure is shown to be identical to that observed by 1H-NMR spectroscopy in solution under slightly acidic conditions, where the N (l) positions of the nucleotides are protonated. The results are discussed in reference to closely related systems reported in the literature with emphasis on the importance of hydrogen bonding in such complexes.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971301032
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  • 2
    Digitale Medien
    Digitale Medien
    Kinetics and Mechanism of Substitution Reactions of cis-[PtMe2(dmso)2] with Pyridine (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1791-1799 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Platinum substitution ; Metal-carbon bonds ; trans-Labilization ; Kinetics ; Activation parameters ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The substitution reactions of cis-[PtMe,(dmso),] with pyridine (py) to produce cis-[PtMe2py2] in toluene proceeds in two steps. In the absence of added dimethylsulfoxide (dmso), these steps can not be separated due to the rate constants being very similar. In the presence of added dmso, the rate of the first step, the formation of the monopyridine complex is retarded, which is indicative of a dissociative mechanism. A parallel associative reaction path with pyridine could also be observed. This pathway is independent of the concentration of added dmso. Above a 40-fold excess of dmso, the dissociative pathway is suppressed and only the associative reaction occurs. A plot of Kobs vs the pyridine concentration for this pathway is linear at low [py], but shows a saturation at high [py]. This suggests that the reaction occurs via the formation of a precursor-complex, for which the formation constant was found to be 0.32 · 0.03 M-1. The volume of activation at a high pyridine concentration is -11.4 · 0.8 cm3 mol-1, which indicates that the ligand interchange process is of the associative type. The second step, the formation of the bispyridine complex, can clearly be separated from the first reaction step. This step occurs via a dissociative mechanism, as demonstrated by the decrease in kobs with increasing pyridine concentration. The dissociation of dmso was characterized by a rate constant of (8.1 · 0.9).10-45-1 at 25°C, ·H = 116 ·9 kJ mol-1 and AS. = 86 · 29 JK-1 mol-1. At higher pyridine concentrations evidence for a parallel associative reaction was found, for which the rate constant is (1.3 · 0.2).10-3 M-1S-1 25°C. The results are discussed in reference to available literature data.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19971301214
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  • 3
    Digitale Medien
    Digitale Medien
    A Spectroscopic and Mechanistic Study of the Enolization and Diol Formation of Hexafluoroacetylacetone in the Presence of Water and Alcohol (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 315-320 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Acetylacetone, hexafluoro- ; Diol formation / Enolization ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Eine spektroskopische und mechanistische Untersuchung der Enolisierung und Diol-Bildung von Hexafluoracetylaceton in Gegenwart von Wasser und AlkoholDie Reaktionen von Hexafluoracetylaceton (Hfac) (6) mit Wasser, Methanol, Ethanol und Isopropylalkohol wurde im einzelnen anhand von 1H-, 13C-, 17O-, 19F-NMR- und UV-VIS-Spektroskopie untersucht. Dabei konnten die Zwischen- und Reaktionsprodukte bei der Enolisierung und Diol-Bildung spektroskopisch identifiziert werden. Die vorgeschlagenen Reaktionswege werden unter Bezug auf früher in der Literatur berichtete Daten diskutiert. Ein wichtiges Ergebnis dieser Untersuchung ist der direkte Nachweis für die Bildung der Addukt-Spezies Hfac(OH)4 (10), Hfac(OMe)2 (13a) und Hfac(OEt)2 (13b).
    Notizen: The reactions of hexafluoroacetylacetone (hfac) (6) with water, methanol, ethanol, and isopropyl alcohol were studied in detail using 1H-, 13C-, 17O-, 19F-NMR, und UV-VIS spectroscopy. The reported spectra enable the identification of intermediate and product species, and allow a mechanistic analysis of the enolization and diol formation. The suggested mechanisms are discussed with reference to earlier data reported in the literature. An important feature of this study is the direct evidence presented for the formation of the adduct species hfac(OH)4 (10), hfac(OMe)2 (13a), and hfac(OEt)2 (13b).
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19891220218
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