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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 109 (1976), S. 1195-1203 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organic Metal Complexes, XIII: Anisotropy Effects in the N. M. R. Spectra of metal Chelates of 3-Mesityl- and 3-(9-Anthryl)acetylacetone3-Mesityl- and 3-(9anthryl)-2,4-pentanedione (1 and 2) have been synthesized by heating tris[3-(bromo)acetylacetonato]chromium and iodomesitylene or 9-bromoanthracene with copper powder. Their complexes with Li, Na, K, Be, Al, Co, Pd, and Tl (1a-i) do not possess magnetic anisotropies in the chelate rings comparable with those of aromatic systems. This is shown in the n. m. r. spectra by means of the chemical shift differences of the o- and p- methyl signals (Δδ ≍ 0.1 ppm). Some boron chelates (7-9) have been investigated, too.
    Notes: Durch Erhitzen von Tris[3-(brom)acetylacetonato]chrom und jodmesitylen bzw. 9-Bromanthracen mit Kupferpulver werden 3-(Mesityl)- bzw. 3-(9-Anthryl)acetylaceton (1 and 2) dargestellt. Die NMR-Spektren der Chelatkomplexe mit Li, Na, K, Be, Al, Co, Pd und Tl (1a-i) zeigen an den Verschiebungsdifferenzen der o- und p-Methylsignale (Δδ ≍ 0.2 ppm) und für die Signale der 1-H und 4-H Atome am Anthrylrest (Δδ ≍ 0.1 ppm), daß diese Metallchelate keine mit aromatischen Systemen vergleichbare magnetische Anisotropie besitzen. Auch Borchelate (7-9) wurden untersucht.
    Additional Material: 2 Tab.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 109 (1976), S. 1184-1194 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Anisotropy Effects of Conjugated Cyclic Systems, I: N.M.R. Spectra of Mesityl- and (9-Anthryl)-substituted Aromatic CompoundsThe chemical shift differences Δδ of the n. m. r. signals of o-and p-methyl-groups in mesityl-substituted ring system are a measure of the magnetic anisotropy of aromatic systems. The same applies to the Δδ of the 1-H and 4-H signals of (9-anthryl)-substituents, but to a greater extent. The Δδ values for benzene, mesitylene, and anthracene as well as for pyrimidine, pyrazole, and isoxazole are reported and discussed.
    Notes: Die Differenz der chemischen Verschiebung Δδ von o-und p-Methylgruppen-Signalen in den NMR-Spektren mesitylsubstituierter Ringsysteme ist ein brauchbares Maß für die magnetische Anisotropie aromatischer Verbindungen. Das gleiche gilt noch verstärkt für die 1-H- und 4-H-Signale eines (9-Anthryl)-Substituenten. Δδ-Werte für Benzol, Mesitylen und Anthracen sowie Pyrimidin, Pyrazol und isoxazol werden mitgeteilt und besprochen.
    Additional Material: 1 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 83 (1971), S. 239-249 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Schwingungsspektren 2H-, 13C- und 18O-markierter Moleküle zeigen an, daß in allen untersuchten Metallchelaten des 2,4-Pentandions (Acetylacetons) der Ausgleich zwischen Doppel- und Einfachbindungen im sechsgliedrigen Ring vollständig ist, im 2,4-Pentandion selbst jedoch nicht. Quecksilber dagegen bindet die Liganden am mittleren C-Atom. Die Kernresonanzspektren der Metallchelate des 3-Mesityl- und 3-Anthryl-2,4-pentandions lassen erkennen, daß die Chelatringe keine mit der des Benzols vergleichbare magnetische Anisotropie besitzen. Es wird kritisch erwogen, wieweit es überhaupt sinnvoll ist, den Bindungszustand solcher Moleküle mit einem „aromatischen Charakter“ in Beziehung zu bringen und warum alle Vergleiche in der chemischen Reaktionsfähigkeit mit der des Benzols bisher zu umstrittenen Aussagen über den Bindungscharakter in den Metallchelaten des Pentandions geführt haben.
    Additional Material: 13 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 10 (1971), S. 225-235 
    ISSN: 0570-0833
    Keywords: β-Diketone metal chelates ; Chelates ; Bond theory ; Pentanedionates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The vibrational spectra of molecules labeled with 2H, 13C, and 18O show that delocalization of double and single bonds in the six-membered ring is complete in all the metal chelates investigated of 2,4-pentanedione (acetylacetone), but not in 2,4-pentanedione itself. Mercury, on the other hand, is bonded to the central C atom of the ligands. The NMR spectra of the metal chelates of 3-mesityl-2,4-pentanedione and 3-anthryl-2,4-pentanedione show that the chelate rings have no magnetic anisotropy comparable with that of benzene. A critical appraisal is made of the questions whether it is at all justifiable to attribute any “aromatic character” to such molecules and why all comparisons with the chemical reactivity of benzene have so far led to controversial conclusions concerning the character of the bonding in the metal chelates of 2,4-pentanedione.
    Additional Material: 13 Ill.
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