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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Geologische Rundschau 85 (1996), S. 19-28 
    ISSN: 0016-7835
    Keywords: Key words Anastomoses ; Crystal zoning ; Snow bands ; Liesegang rings ; Ostwald ripening ; Self organization ; Siderite ; Supersaturation theory ; Zebra rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Morphological instabilities in periodic patterns occurring both in precipitation and crystallization processes (Liesegang rings and crystal zoning) are investigated and compared with similar patterns in geological samples (zebra rocks and mud bands in snow sediments). In classical Liesegang systems, undisturbed parallel or concentric precipitation bands are emanated from even or concentric diffusion sources in homogeneous diffusion matrices of gelatine or other gels. In the case of superposing diffusion sources, sources with undulatory curvatures or local diffusion barriers there may occur several types of instabilities within the sequence of regular patterns: (a) gaps within the bands forming radial alleys free of precipitate, (b) transition from broken bands to speckled patterns and (c) apparent branching of bands linked together by so-called anastomoses. Calculations with a competitive particle growth (CPG) model show that lateral instabilities in Liesegang bands (gaps and radial alleys of gaps) are the result of Ostwald ripening effects taking place after precipitation. Apparent branching of bands or formation of anastomoses can be simulated with a prenucleation model according to Ostwald's supersaturation theory. Similar irregularities can be observed in zebra rocks (e.g. banded siderite) whose bandings are commonly explained by sequential sedimentation processes. A very different mechanism is assumed to be responsible for the origin of mud bands in snow sediments. An initially homogeneous distribution of intrinsic mud in snow sediments can be arranged into parallel bands according to a crystal zoning mechanism which is based on repeated thawing and freezing of the snow sediment due to the daily alternation of sun and darkness.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 3 (1980), S. 85-86 
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; Ion-pair reversed-phase ; Free porphyrin carboxylic acids in urine, complete separation ; Quantitation within 4.4-5.4% precision ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 3
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of the dimethylphosphinic, dimethylthiophosphinic and dimethylphosphinous ester derivatives of several monohydroxy steroids are reported. The fragmentations of the derivatized steroids largely depend on the nature of the the phosphorus-containing ester group. Phenolic ester derivatives exhibit the base peak at the molecular ion, whereas the spectra of the secondary phosphinic esters are dominated by very intense protonated phosphinic acid ions [Me2 P(XH)(OH)]+ at m/e 95 (X = O) or at m/e 111 (X = S). The present results also indicate the low ionization potential for the phosphinic ester group. Due to their good gas chromatographic properties, these steroid derivatives appear to be particularly suitable for gas chromatographic mass spectrometric analysis of biochemical materials.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of earth sciences 85 (1996), S. 19-28 
    ISSN: 1437-3262
    Keywords: Anastomoses ; Crystal zoning ; Snow bands ; Liesegang rings ; Ostwald ripening ; Self organization ; Siderite ; Supersaturation theory ; Zebra rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Morphological instabilities in periodic patterns occurring both in precipitation and crystallization processes (Liesegang rings and crystal zoning) are investigated and compared with similar patterns in geological samples (zebra rocks and mud bands in snow sediments). In classical Liesegang systems, undisturbed parallel or concentric precipitation bands are emanated from even or concentric diffusion sources in homogeneous diffusion matrices of gelatine or other gels. In the case of superposing diffusion sources, sources with undulatory curvatures or local diffusion barriers there may occur several types of instabilities within the sequence of regular patterns: (a) gaps within the bands forming radial alleys free of precipitate, (b) transition from broken bands to speckled patterns and (c) apparent branching of bands linked together by so-called anastomoses. Calculations with a competitive particle growth (CPG) model show that lateral instabilities in Liesegang bands (gaps and radial alleys of gaps) are the result of Ostwald ripening effects taking place after precipitation. Apparent branching of bands or formation of anastomoses can be simulated with a prenucleation model according to Ostwald's supersaturation theory. Similar irregularities can be observed in zebra rocks (e.g. banded siderite) whose bandings are commonly explained by sequential sedimentation processes. A very different mechanism is assumed to be responsible for the origin of mud bands in snow sediments. An initially homogeneous distribution of intrinsic mud in snow sediments can be arranged into parallel bands according to a crystal zoning mechanism which is based on repeated thawing and freezing of the snow sediment due to the daily alternation of sun and darkness.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 421 (1976), S. 129-134 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Transition Metal Alkyl Compounds. XVIII. On the Preparation and Properties of Tetrabenzyl Vanadium and Benzyl Tantalum ChloridesPure tetrabenzyl vanadium was isolated and characterized by elementary analyses, EPR and 1H-NMR spectra, by hydrolysis and thermal decomposition.  -  Experiments for the preparation of tetra or pentabenzyl compounds of niobium and tantalum failed, but we could prepare C6H5CH2TaCl4, (C6H5CH2)2TaCl3, and (C6H5CH2)3TaCl2, the last two in form of bipyridyl complexes.
    Notes: Vanadintetrabenzyl wurde in definierter Form isoliert und durch Elementaranalyse, ESR- und 1H-NMR-Spektrum sowie durch die hydrolytische und thermische Spaltung charakterisiert.  -  Versuche zur Gewinnung von Tetra- und Pentabenzylverbindungen des Niobs und Tantals blieben erfolglos. Es gelang jedoch, die Verbindungen C6H5CH2—TaCl4, (C6H5CH2)2TaCl3 und (C6H5CH2)3TaCl2, zum Teil in Form von Dipyridylkomplexen, zu gewinnen.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 455 (1979), S. 3-12 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Transition Metal Alkyl Compounds. XXIX. Dibenzyl Manganese - Preparation and ReactionsManganese(II) acetylacetonate reacts with tribenzyl aluminium and dibenzyl magnesium forming the yellow complexes 3(C6H5CH2)2Mn · Al(acac)3 and (C6H5CH2)2Mn · Mg(acac)2 Dibenzyl manganese is also formed at the reaction of dibenzyl magnesium or benzyl magnesium chloride with MnCl2 · 1.5 THF and was separated as the dioxan complex (C6H5CH2)2Mn · 2C4H8O2, the ligands of which can be removed to a great extent in vacuum.Dibenzyl manganese reacts with CO2, CS2 and SO2 with insertion into the Mn-C-bonds. The corresponding manganese compounds were isolated and furtherly characterized.
    Notes: Mangan(II)-acetylacetonat reagiert mit Tribenzylaluminium bzw. Dibenzylmagnesium zu den gelben Komplexen 3(C6H5CH2)2Mn · Al(acac)3 bzw. (C6H5CH2)2Mn Mg(acac)2. Dibenzylmangan entsteht auch bei Einwirkung von Dibenzylmagnesium oder Benzyl magnesiumchlorid auf MnCl2 · 1,5 THF; eine Abtrennung von den Magnesiumsalzen gelingt in Form des 1,4-Dioxankomplexes (C6H5CH2)2Mn · 2C4H8O2, dessen Ligandenmoleküle im Vakuum weit gehend entfernt werden können.Dibenzylmangan reagiert mit CO2, CS2 und SO2 unter Insertion in die Mn-C-Bindungen. Die entsprechenden Mangansalze wurden isoliert und näher charakterisiert.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 498 (1983), S. 115-120 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Transition Metal Alkyl Compounds. XXXIV. Synthesis and Properties of 3-(N,N-dialkylamino)propyl Manganese CompoundsMnCl2 reacts with lithium organyls of the type R2N(CH2)3Li with formation of definite organomanganese complexes. The pure [(CH3)2N(CH2)3]2Mn, [(C2H5)2N(CH2)3]2Mn, [(CH2)5N(CH2)3]2Mn and the complexes [(CH3)2N(CH2)3]2Mn · LiCl and Li{Mn[(CH2)3N(CH3)2]3} · 1,5 THF were isolated.[(CH3)2N(CH2)3]2Mn · 2 Li(acac) was obtained as a result of reactions of Mn(acac)2 and Mn(acac)3 with the corresponding lithium organyl.The σ-organomanganese(II) derivatives were characterized in detail by elementary analysis, molecular weight determination, ESR- and IR-spectra, conductivity measurements and the magnetic moments.
    Notes: MnCl2 reagiert mit Lithiumorganylen des Typs R2N(CH2)3Li zu definierten Organomanganverbindungen. In reiner Form wurden [(CH3)2N(CH2)3]2Mn, [(C2H5)2N(CH2)3]2Mn, [(CH2)5N(CH2)3]2Mn und Komplexe der Zusammensetzung [(CH3)2N(CH2)3]2Mn · LiCl und Li{Mn-[(CH2)3N(CH3)2]3} · 1,5 THF isoliert. Ausgehend von Mn(acac)2 und Mn(acac)3 wurde [(CH3)2N(CH2)3]2Mn · 2 Li(acac) erhalten.Die nähere Charakterisierung der σ-Organomangan(II)-Derivate erfolgt durch Elementaranalysen, kryoskopische Molmassebestimmungen, ESR- und IR-Untersuchungen, Leitfähigkeitsmessungen und Ermittlung der magnetischen Momente.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 511 (1984), S. 89-94 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Transition Metal Alkyl Compounds. XXXVIII. Reactions of Dibenzyl Manganese with Oxygene(C6H5CH2)2Mn · C4H8O2 reacts with oxygen forming an unstable deep violet compound which changes in a stable unsoluble yellow peroxide of the formula C6H5CH2MnO—OMnCH2C6 H5. With excess oxygen a polynuclear complex of 3 valent manganese is formed with the composition Mn4O4(OH)4(OCHC6H5)2.The compounds isolated were characterized by the products of hydrolyses and thermolyses, anaerobic reaction with iodine, magnetic moments, i.r. and e.s.r. spectra.
    Notes: Dibenzylmangan-1,4-dioxan reagiert mit Sauerstoff zu einer tiefvioletten instabilen Substanz. Diese wandelt sich in ein stabiles gelbes, schwerlösliches Peroxid der Formel C6H5CH2MnO—OMnCH2C6H5 um. Mit überschüssigem Sauerstoff entsteht daraus ein Mehrkernkomplex des 3wertigen Mangans der Zusammensetzung Mn4O4(OH)4(OCHC6H5)2.Die isolierten Verbindungen wurden durch ihre Hydrolyse- und Thermolyseprodukte, anaerobe Iodierung, magnetischen Momente sowie IR- und ESR-Spektren näher charakterisiert.
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  • 9
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The interaction between alkyl magnesium halides and titanium(IV)-chloride and -bromide in nonpolar solvents is investigated. The reaction products, mostly mixtures of two substances, were isolated in the form of thermally stable complexes with 2,2′-bipyridyl.
    Notes: Es wird über die Einwirkung ätherfreier Alkylmagnesiumhalogenide auf Titan(IV)-chlorid und Titan(IV)-bromid in unpolaren Lösungsmitteln berichtet. Die entstehenden Reaktionsprodukte, meist Substanzgemische, wurden als thermisch stabile 2,2′-Dipyridyl-komplexe isoliert.
    Additional Material: 1 Ill.
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  • 10
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Transition Metal Alkyl Compounds. XII. On Attempts to prepare Benzyl Compounds of Nickel, Cobalt, and IronReport about attempts to prepare benzyl compounds of nickel, cobalt and iron by reactions of halides of these metals, triaryl and trialkylphosphine complexes of nickel and cobalt halides, bis(cyclooctadiene-1,5)nickel and tetrakis(triphenylphosphine)-nickel with several benzylating agents. In the course of some reactions the intermediate formation of instable benzyl compounds seems to occur, but an isolation failed in each case.
    Notes: Bericht über Versuche zur Benzylierung von Nickel-, Kobalt-und Eisenhalogeniden, Triaryl- und Trialkylphosphinkomplexen von Nickel- und Kobalthalogeniden, Nickel-bis-cyclooctadien und Nickeltetrakis-triphenylphosphin mit verschiedenen Benzylierungsreagenzien. Bei einigen der Reaktionen erfolgte offensichtlich intermediär die Bildung instabiler Benzylmetallverbindungen, doch gelang in keinem Falle deren Isolierung.
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