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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 108 (1975), S. 3096-3104 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Intramolecular Hydrogen Bond in 6-hydroxy-1-fulvenecarbaldehydeThe title compound 1 (C7O2H6) crystallizes in the space group Pbca, Z = 8, a = 7.70, b = 14.35, c = 10.95 Å. The structure has been determined by X-ray and neutron diffraction experiments. The refinements gave conventional R-factors of 0.076 and 0.070, respectively. The distance between the oxygen atoms was found to be 2.513 (X-ray) and 2.550 Å (neutron diffraction). The neutron diffraction investigation sowed a slightly unsymmetric hydrogen bond with O—H distances of 1.343 and 1.214 Å. The O—H—O angle is 171.2°.
    Notes: 6-Hydroxy-1-fulvencarbaldehyd C7O2H6 (1) kristallisiert in der Raumgruppe Pbca, Z = 8, a = 7.70, b = 14.35, c = 10.95 Å. Die Struktur wurde durch Röntgen- und Neutronenbeugungs-experimente bestimmt. Die Verfeinerungen führten zu konventionellen R-Faktoren von 0.076 bzw. 0.070. Der Abstand zwischen den beiden Sauerstoffatomen ergab sich zu 2.513 (Röntgenbeugung) bzw. 2.550 Å (Neutronenbeugung). Nach den Ergebnissen der Neutronenbeugungsuntersuchungen ist die Wasserstoffbrücke unsymmetrisch, wobei die O—H-Abstände 1.343 und 1.214 Å betragen. Der O—H—O-Winkel wurde zu 171.2° bestimmt.
    Additional Material: 1 Tab.
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 827-832 
    ISSN: 0009-2940
    Keywords: Conformations, solid state ; Conformers in solution ; UV-Vis transition energies and CO/CO dihedral angles ; CO/CO rotational barriers ; Calculations, CNDO/S-CI, MMP1, PIMM / PE spectroscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chromophoric Systems, 2. - Conformation and Absorption of Light in (2-Alkoxyvinyl)ethanedionesThe unusual color properties of yellow 1,2-bis(4,5-dihydrofuran-3-yl)ethane-1,2-dione (1) and colorless 1,2-bis(5,6-dihydro-4H-pyran-3-yl)ethane-1,2-dione (2) in the solid state and in solution are investigated by crystal structure analysis, UV-Vis, PE, and 13C-NMR spectroscopy as well as by reparameterized force-field calculations. Dione 1 takes an antiperiplaner CO/CO conformation of its chromophore in the solid state whereas dione 2 is twisted in this respect by 102°. In solution both chromophores are not planar, but 1 is less distorted (ca. 142°) than dione 2 (ca. 126°). The calculated rotational barrier for CO/CO twisting amounts to 0.9 kcal mol-1 for 1 and to 2.2 kcal mol-1 for 2.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 607-613 
    ISSN: 0009-2940
    Keywords: Arene complexes ; Chromium compounds ; Alkynes ; Catalysis ; Coupling reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The palladium-copper-catalyzed coupling of the tricarbonyl-chromium-complexed chlorobenzene 1 with (trimethylsilyl)-acetylene gives tricarbonyl{η6-[(trimethylsilyl)ethynyl]-benzene}chromium(0) (2) in high yield. After desilylation of 2 tricarbonyl[η6-(ethynylbenzene)]chromium(0) (3) is obtained quantitatively. Using the palladium-copper-catalyzed methodology, we can readily introduce Cr(CO)3-complexed phenylethynyl units by a multifold coupling of 3 with iodobenzene, 1,2-, 1,3-, 1,4-di- and 1,3,5-tiiodobenzene (4a-e) or 1 to give polynuclear Cr(CO)3-complexed (phenylethynyl)benzenes 5a-e and doubly Cr(CO)3-complexed tolane 6 in good to moderate yield. The crystal structure analyses of μ3-{η6:η6:η6[1,3,5-benzenetriyltris(2,1-ethynediyl)]tris(benzene)}tris[tricarbonylchromium(0)] (5e) and μ-{η6:η6-[1,2-ethynediylbis(benzene)]}bis[tricarbonylchromium(0)] (6) reveal that the tricarbonylchromium tripods in the same molecule are arranged in antiparallel syn-eclipsed conformations. The Eglington coupling of 3 affords a doubly Cr(CO)3-complexed diphenylbutadiyne 7 in excellent yield.
    Additional Material: 2 Ill.
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  • 14
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermolabile Hydrocarbons, XXV1). Relationships between Thermal Stability, Strain, and Structure of 1,1′-Diphenyl-1,1′-bicycloalkylsThe products and activation parameters of the thermolysis reaction of the title hydrocarbons 1a (n = 4-8) and 1b (n = 12) were determined. Strain enthalpies and structural data of the compounds 1a and of the radicals 2a, which are generated on thermolysis, were obtained from force field calculations. For 1a (n = 8) a crystal structure analysis was carried out.  -  The importance of i-strain action is estimated from the relationship between ΔG≠ of the thermolysis reaction and the strain enthalpy of 1 from which the ring strain of the corresponding cycloalkane was substracted as a correction factor. In addition, a linear correlation between ΔG≠ and the change in strain enthalpy (MM2 results) in the course of the dissociation process was found. The large variation in ΔS≠ can be rationalized by consideration of the change in internal mobility (MM2 results) during the dissociation process.
    Notes: Die Produkte und Aktivierungsparameter der Thermolyse der Kohlenwasserstoffe 1a (n = 4-8) und 1b (n = 12) wurden bestimmt. Die Spannungsenthalpien und Strukturdaten der Verbindungen 1a und der beim thermischen Zerfall entstehenden Radikale 2a wurden durch Kraftfeldberechnungen ermittelt. Für 1a (n = 8) wurde eine Kristallstrukturanalyse durchgeführt.  -  Die Beziehungen zwischen ΔG≠ der Thermolyse und den um die Ringspannung korrigierten Spannungsenthalpien gestatten eine quantitative Analyse der i-strain-Wirkung. Außerdem wird eine lineare Korrelation zwischen ΔG≠ und der Änderung an Spannungsenthalpie im Dissoziationsprozess nach Kraftfeldrechnungen aufgezeigt. Stark unterschiedliche Aktivierungsentropien werden durch die Änderung der inneren Beweglichkeit im Zuge des Dissoziationsprozesses, die aus Kraftfeldrechnungen abschätzbar ist, verständlich.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 15
    ISSN: 0009-2940
    Keywords: Charge-transfer complexes ; Electric conductivity ; Segregated stacking ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conducting Charge-Transfer Complexes of 2,5-Bis(cyanoimino)-2,5-dihydrothieno[3,2-b]thiophenes with Organic DonorsFrom the title compound 4 and several donors 13 charge-transfer (CT) complexes have been obtained. Most of them show powder conductivities of 0.01-2.0 Scm-1. The crystal structure of 4d/TTF (20 Scm-1) reveals segregated stacks of donor and acceptor molecules in a novel stacking pattern. The structure of 4d/TMTSF consists of mixed stacks (insulator), however a second phase (no structure available) exhibits very high conductivity (200 Scm-1).
    Additional Material: 7 Ill.
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  • 16
    ISSN: 0009-2940
    Keywords: Arene complexes ; Chromium compounds ; Substituent effects ; Push-pull chromophores ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tricarbonylchromium complexes chlorobenzene 1 reacts with terminal alkynes 2 through a palladium-copper-catalyzed coupling to give a variety of Cr(CO)3-complexed phenylethynyl arenes, heteroarenes and ferrocene 3 in good to excellent yield. Due to the electron-withdrawing nature of the Cr(CO)3 group these novel complexes can be regarded as organometallic push-pull chromophores. Analogously, the corresponding free ligands 4 (phenylethynyl arenes, heteroarenes and ferrocene) were synthesized by coupling iodobenzene and 2. The crystal structure analysis of the singly Cr(CO)3-complexed tolane 3e reveals a strong deviation from coplanarity of both phenyl rings by an angle of 50.9(2)° presumably due to crystal packing. Correlations are established between selected substituent parameters (σP, σI, σR, σP+ and Δπ) and the carbonyl carbon resonances in the 13C-NMR spectra for the complexes 3. The overall electronic substituent effect is transmitted to the carbonyl groups by both mesomeric and inductive mechanisms. The push-pull complexes 3 display relatively small negative solvochromicities of longest wavelength absorption band (MLCT band).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 1017-1041 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Substituent Effects on the C—C-Bond Strength, 1. Structure and Strain Enthalpy of Tetrasubstituted SuccinonitrilesEleven Succinonitriles, tetrasubstituted by alkyl or aryl groups, were prepared, partially as pure meso- and DL-diastereomers. For four of them standard heats of formation ΔHfo and strain enthalpies Hsp were determined from heats of combustion. Their values were used together with data from the literature to deduce the CN-base value required for the computation of heats of formation ΔHfo of nitriles and dinitriles with Allinger's MM2 force field. In addition rotational barriers, conformational equilibria, dipole moments and structures were determined by force field calculations. The agreement with experimental data as e. g. the X-ray structures of 7d und 7g was good. The relationships between strain and structure are discussed.
    Notes: Elf durch Alkyl- oder Arylgruppen tetrasubstituierte Bernsteinsäuredinitrile wurden, teilweise als meso- und DL-Diastereomere, dargestellt. Durch Verbrennungskalorimetrie wurden von vier Bernsteinsäuredinitrilen Bildungsenthalpien ΔHfo und Spannungsenthalpien Hsp bestimmt, die es, zusammen mit Literatur-Werten ermöglichten, das Kraftfeld MM2 zur Berechnung der Bildungswärmen ΔHfo von Nitrilen und Dinitrilen zu parametrisieren. Mit dem Kraftfeld wurden zusätzlich Rotationsbarrieren, Konformationsgleichgewichte, Dipolmomente und Strukturen berechnet. Die Übereinstimmung mit experimentellen Werten, u.a. den Röntgenstrukturanalysen der Dinitrile 7d und 7g, ist gut. Die Zusammenhänge zwischen Strukturparametern und Spannungsenthalpien werden diskutiert.
    Additional Material: 7 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 3235-3263 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermolabile Hydrocarbons, XX. Synthesis, Structure, and Strain of Sym. Tetraalkyl-1,2-diarylethanesThe syntheses of 18 1,1,2,2-tetraalkyl-1,2-diarylethanes 1-4 by dimerisation procedures starting with 10-13 are reported. In the absence of p-substituents X and with increasing alkyl side chains the α, p-dimers 6 or their aromatic counter parts 7 are obtained besides or instead of 1. The relationships between strain enthalpy Hs, bond lengths, bond angles, torsional angles, and rotational barriers are discussed on the basis of force field calculations. They are supported by two additional experimental structure determinations by X-ray diffraction.
    Notes: Die Synthesen von 18 1,1,2,2-Tetraalkyl-1,2-diarylethanen 1-4 durch Dimerisierungsverfahren ausgehend von 10-13 werden beschrieben. Bei fehlenden p-Substituenten X und großen Alkylseitenketten R1 und R2 erhält man neben oder statt 1 α, p-Dimere 6 oder deren aromatische Folgeprodukte 7. Die Zusammenhänge zwischen Spannungsenthalpie Hs und Bindungslängen und -winkeln sowie Torsionswinkeln und Rotationspotentialen werden anhand von Kraftfeldberechnungen diskutiert. Zur Absicherung der Kraftfeldmethode wurden zwei weitere Kristallstrukturanalysen durchgeführt.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 19
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Conformation of Tetravinyl- and Trivinylmethane - Comparison between the PE Spectra of Tetravinylmethane and trans,trans,trans- 1,2,3,4-TetravinylcyclobutaneThe conformations of tetravinylmethane (1) and trivinylmethane (3) have been calculated using a π-SCF force field and the MINDO/3 method. Both methods predict for 1 a conformation of S4 symmetry and for 3 a conformation of C3 symmetry to be most stable. Based on these predictions we discuss the He(I) photoelectron (PE) spectra of 1 and 3. The comparison between the PE spectrum of 1 and that of all-trans-1,2,3,4-tetravinylcyclobutane (2) reveals a similar interaction between the vinyl groups in 2 compared with 1.
    Notes: Die Konformation von Tetravinylmethan (1) und Trivinylmethan (3) wird mit Hilfe einer π-SCF-Kraftfeldrechnung und der MINDO/3-Methode berechnet. Beide Methoden sagen für 1 eine Konformation der Punktgruppe S4 und für 3 der Punktgruppe C3 voraus. Basierend auf diesen Konformationen werden die He(I)-Photoelektronen(PE)-Spektren von 1 und 3 diskutiert. Der Vergleich zwischen dem PE-Spektrum von 1 und dem von all-trans-1,2,3,4-Tetravinylcyclobutan (2) ergibt eine ähnliche Wechselwirkung der Vinylgruppen bei 2.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 20
    ISSN: 0009-2940
    Keywords: Alkylrhodoximes ; Radicals, alkyl ; Halogen abstraction ; Carbon-carbon bond formation ; Stereochemistry ; Photoreactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Primary, secondary, and tertiary alkylrhodoximes 1 were prepared from alkyl bromides and tosylates 4 and the trans1-dichlororhodium complex 3. X-ray crystallography of the previously unknown tert1-butylrhodoxime 1k reveals structural features of this tert-s̰1-alkylrhodium compound. Photochemical homolytic cleavage of the Rh - C bond in alkylrhodoximes 1 only occurs in the presence of efficient radical traps which allow further mechanistic studies.
    Additional Material: 1 Ill.
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