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  • General Chemistry  (1,203)
  • Inorganic Chemistry  (732)
  • 1990-1994  (1,935)
  • 1992  (1,935)
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  • 1990-1994  (1,935)
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  • 1
    Electronic Resource
    Electronic Resource
    Masthead (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250101
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesen neuer bororganischer Ringe mit zwei Bor-Atomen durch Borylierung des Trimethylenmethan-Dianions (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 23-29 
    Details
    ISSN: 0009-2940
    Keywords: Diboracycloalkanes ; Diboracycloalkenes ; Trimethylenemethane, borylation of the dianion of ; Allylboranes, B - C bond length ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of New Organoboron Rings with two Boron Atoms by Borylation of the Trimethylenemethane DianionBorylation of Li2[C(CH2)3] (1) provides a versatile starting point for the synthesis of 5-, 6-, 7-, and 8-membered ring systems with two boron atoms and leads to 1,5-bis(dialkylamino)-3,7-dimethylene-1,5-diboracyclooctanes 2a, b (a: R=Et; b: R=iPr), 1,3-bis(dialkylamino)-5-methylene-1,3-diboracyclohexanes 8a, b, 1,3-bis(diethylamino)-5-methyl-1,3-dibora-4-cyclo-hexene (10), and 1,4-bis(dialkylamino)-6-methylene-1,4-dibora-2-cycloheptenes 11a, b. The compounds 2b, 8b, and the 2,3-biboratafulvene derivative [Li(TMEDA)]2[CH2C(CHB)2-(NiPr2)2] are characterized by X-ray diffraction analysis. It is shown that for trigonal boron B - C(allyl) bond distances (typically 160 ± 1 pm) are significantly larger than B - C(alkyl) distances (typically 158 + 1 pm).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250105
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  • 3
    Electronic Resource
    Electronic Resource
    Trinuclear Homo- and Heterometallic Complexes of a Doubly Bridged Cyclopentadienyl Ligand (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 31-35 
    Details
    ISSN: 0009-2940
    Keywords: Cyclopentadienyl ligand, doubly bridged ; Cyclopentadienyl complexes, trinuclear ; Polymers, organometallic ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal complexes that are derived from the doubly bridged cyclopentadiene system 2,2,8,8-tetramethyl-2,8-disilatricyclo[7.3.0.03,7] dodeca-3,5,9,11-tetraene (LH2) are investigated. The dilithio salt of this compound (LLi2) reacts with (Me3Si)3-C5H2FeCl to give, amongst other products, the trinuclear ferrocene [(Me3Si)3C5H2FeL]2Fe (2). A starting material well suited for the selective preparation of similar trinuclear complexes is the mononuclear ferrocene (HL2)Fe (3) which is formed by reaction of HLLi with iron(II) chloride. Reaction of dilithiiated 3 with trimethyltin chloride yields (Me3SnL)2Fe (4). Cocomplexation of dilithiated 3 and Cp*Li (Cp*=C5Me5) with iron(II) chloride leads to the trinuclear ferrocene (Cp*FeL)2Fe (5). By reaction of 3 with octacarbonyldicobalt the heterometallic complex [(CO)2CoL]2Fe (6) is obtained, which yields [(CO)I2CoL]2Fe (7) by oxidative decarbonylation with iodine. The stereochemistry of the complexes presented is discussed. The trinuclear complexes 2, 5, 6, and 7 are model systems for organometallic polymers with spatially directed structures, whose stability even in mixed-valence states is evidenced by the mass spectra of these complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250106
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  • 4
    Electronic Resource
    Electronic Resource
    Metallkomplexe von Farbstoffen  -  Übergangsmetall-Komplexe mit 2-(1,3-Dioxo-2-indanyliden)benzimidazolinen (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 61-66 
    Details
    ISSN: 0009-2940
    Keywords: Benzimidazoline, 2-(1,3-dioxo-2-indanylidene)-, as chelate ligand ; Copper complexes ; Nickel complexes ; Palladium complexes ; Platinum complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal Complexes of Dyes  -  Transition Metal Complexes of Mono- and Dianions of 2-(1,3-Dioxo-2-indanylidene)-benzimidazolines2-(1,3-Dioxo-2-indanylidene)benzimidazolines (L) (1 - 6) react with metal salts and chloro-bridged complexes in the presence of NaH to give the mono and bis-N,O-chelate complexes (L  -  H+)2M (M=Cu, Pd, Ni) (7 - 9), (L  -  H+)M(PR3)Cl (M=Pd, Pt; 10 - 15 and (L  -  2H+)[Pt(PEt3)Cl]2 (16, 17). The electronic spectra of the bis(chelate) complexes show a large bathochromic shift of the absorptions in the visible region as compared to the free ligands. The structures of (L  -  H+)Pd(Cl)-(PnBu3) (10) and of (L  -  2H+)[Pt(Cl)PEt3)]2 (16) have been determined by X-ray crystallography. The two heterocyclic planes in 16 are bent along the elongated central C=C bond [143.2(12)pm] which gives a hip-roof-like structure.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250111
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  • 5
    Electronic Resource
    Electronic Resource
    Metal Complexes with Tetrapyrrole Ligands, LXI. Structure and Products of Electrochemical Oxidation of Zirconium(IV) and Hafnium(IV) Bisporphyrinate Double-Deckers (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 107-115 
    Details
    ISSN: 0009-2940
    Keywords: Zirconium porphyrins ; Hafnium porphyrins ; Porphyrin double-deckers ; Metal bisporphyrinates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemical oxidation of zirconium and hafnium double-deckers M(P)2 (M=Zr, Hf; P=OEP, TPP) (Scheme 1)2) leads to mono- and dications which show near infrared absorption bands which are of ≈ 2000 cm-1 higher energy than those of the corresponding cerium double-decker cations. [Zr(OEP)2]X, [Zr(OEP)2]X2, and [Zr(TPP)2]X (X=ClO4- and PF6-) are isolated after electrochemical oxidation and are characterized by IR and NMR spectroscopy. Magnetic susceptibility measurements (2 K 〈 T 〈 300 K) of the solids confirm the strong coupling of the electron spins in the diamagnetic dication salt [Zr(OEP)2][ClO4]2. The molecular structure of Zr(OEP)2 is elucidated by an X-ray structural analysis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250118
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  • 6
    Electronic Resource
    Electronic Resource
    Mehrfachbindungen zwischen Hauptgruppenelementen und übergangsmetallen, CII. Flüchtige MN4-Metallkomplexe von Niob und Tantal mit Dimethylsilyl-Substituenten (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 117-118 
    Details
    ISSN: 0009-2940
    Keywords: Imido ligands ; Amido ligands ; Niobium complexes ; Tantalum complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multiple Bonds between Main-Group Elements and Transition Metals, CII[1].  -  Volatile MN4 Metal Complexes of Niobium and Tantalum Containing Dimethylsilyl SubstituentsNiobium and tantalum complexes 4a and 4b of formula (Me2SiH)N=M[N(SiHMe2)2]3 (a: M=Nb; b: M=Ta) are formed from lithium bis(dimethylsilyl)amide and either MOCl3 (2a,b) or MCl5 (3a,b). No β-hydrogen decomposition of these compounds occurs under normal conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250119
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  • 7
    Electronic Resource
    Electronic Resource
    Organomolybdän- und Organowolfram-Reagenzien, II. über den carbonylolefinierenden μ-Methylenkomplex aus Mo2Cl10 und vier äquivalenten Methyllithium (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 143-148 
    Details
    ISSN: 0009-2940
    Keywords: Carbonyl olefination ; μ-Methylene complexes ; Molybdenum complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organomolybdenum and Organotungsten Reagents, II.  -  On the Carbonyl-Olefinating μ-Methylene Complex from Mo2Cl10 and Four Equivalents of MethyllithiumMo2Cl10 reacts at  -  70°C with 4 equivalents of methyllithium to give a methylated thermolabile molybdenum complex. At higher temperatures it forms a thermolabile carbonyl-olefinating reagent which according to NMR data is the μ-CH2 complex Cl3Mo(μ-CH2)2MoCl3 (2). Reactions of 2 with aldehydes, ketones, azomethines, and epoxides are described.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250123
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  • 8
    Electronic Resource
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    Alkyleisen- und Alkylcobalt-Reagenzien, III. Nichtstabilisierte Eisenalkyle: Bildung, Nachweis und Chemoselektivität (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 163-169 
    Details
    ISSN: 0009-2940
    Keywords: Iron ; organo reagents ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkyliron and Alkylcobalt Reagents, III.  -  Nonstabilized Ironalkyls: Formation, Detection, and ChemoselectivityThe crystalline ate complex Me4FeLi2(Et2O)2 (1 d) described in the literature as well as the complexes MeFeCl (1a), Me2Fe (1b), Me3FeLi (1c), nBu2Fe (2 a), nBu4FeLi2 (2b), nOct2Fe (3a), nOct3FeLi (3b), and nOct4FeLi2 (3c) are prepared in situ by transmetallation of MeLi, nBuLi, and nOctLi with FeCl2 (readily available by in situ reduction of FeCl3 with MeLi). All these complexes have been subjected to reaction with organic substrates for the first time. Evidence for this transmetallation has been furnished by a novel test (referred to as “β-bromostyrene-ketone test”). In this test, involving addition of β-bromostyrene (4) and 4-methylpentan-2-one (5), the alkyllithium compounds alkylate selectively only the ketone and the alkyliron compounds almost exclusively the β-bromostyrene. The high preference of the alkyliron reagents for the alkylation of the β-bromostyryl residue has been utilized for regioselective butylations and octylations of 1-{4-[(Z)-2-bromoethenyl]phenyl}-ethanone (6). Moreover, in competition reactions with benzaldehyde/4-methylpentan-2-one the alkyliron reagents have been found to react usually specifically with aldehydes. The decomposition temperatures of the reagents 1a,b,c and 2b in THF have been determined to be 0, -10, 25, and -20°C, respectively.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250127
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  • 9
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    Übergangsmetallaktivierte organische Verbindungen, XXXV. Ortho-Alkylierungen von aromatischen Azoverbindungen mit Alkyllithium-Reagenzien und Lithiumtrimethylferrat(1-) (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 153-155 
    Details
    ISSN: 0009-2940
    Keywords: Lithium, organo compounds ; Iron, organo compounds ; Azo compounds ; ortho-Alkylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transitional-Metal-Activated Organic Compounds, XXXV.  -  ortho-Alkylation of Aromatic Azo Compounds with Alkyllithium Reagents and Lithium Trimethylferrate(1-)Whereas methyllithium reacts with 4-(dimethylamino)-, 4-amino-, and 4-methoxyazobenzene, respectively, by ortho-methylation of the electron-rich phenyl residue of the azo compound, (CH3)3FeLi ortho-methylates the less electron-rich phenyl group of 4-(dimethylamino)azobenzene. A mechanistic rationalisation is given for both reaction modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250125
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  • 10
    Electronic Resource
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    7-Substituierte Cycloheptatriene als Dienophile in der Diels-Alder-Cycloaddition mit inversem Elektronenbedarf (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 171-176 
    Details
    ISSN: 0009-2940
    Keywords: Cycloheptatriene ; Norcaradiene ; Valence isomerization ; [4 + 2] Cycloadditions ; Site selectivity ; Valence isomer selectivity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 7-Substituted Cycloheptatrienes as Dienophiles in the Diels-Alder Cycloaddition With Inverse Electron DemandA series of 7-substituted cycloheptatrienes 1, including CN, CO2CH3, C6H5, C(CH3)3, CH3, CH(OCH3)2, H, N(CH3)2 groups has been submitted to inverse [4 + 2] cycloaddition with 3,6-bis(trifluoromethyl)-1,2,4,5-tetrazine (5). Reaction of 5 with π-acceptor-substituted cycloheptatrienes such as 1a-c leads exclusively to cyclopropa[f]phthalazines 8 and 9, whereas 7-alkylcycloheptatrienes 1d-f give mixtures of cyclopropa[f]phthalazines 10 and 12 and 7H-cyclohepta[d]pyridazines 11 and 13. Moreover, 7-methylcycloheptatriene (1e) yields three further products 19, 20, 21, derived from heptafulvene 16, formed intermediately by dehydrogenation of 1e. In contrast to 1a - f, reaction of 5 with cycloheptatriene (1g) yields the corresponding 5H-cyclohepta[d]pyridazine 22 quantitatively. Surprisingly, no [4 + 2] cycloadducts are observed with the π-donor-substituted cycloheptatriene 1h. Instead, the indazol 27 and the triazoles 25 and 28 are formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250128
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  • 11
    Electronic Resource
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    Alkylvanadium- und Alkylniobium-Reagentien, II. Niobium-induzierte reduktive Carbonyldimerisierung (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 149-151 
    Details
    ISSN: 0009-2940
    Keywords: Reductive carbonyl dimerisation ; Niobium pentachloride ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkylvanadium and Alkylniobium Reagents, II.  -  Niobium-Induced Reductive Carbonyl DimerisationNbCl5 reacts with one equivalent of methyllithium or metallic potassium to give a reagent for the transformation of aldehydes, ketones, benzalchloride, and benzotrichloride to symmetrically substituted ethene derivatives (Tab. 1). The reagent NbCl5/K (2) is distinctly more reactive than NbCl5/MeLi (1). For the reductive carbonyl dimerisation with niobium reagents a mechanism is proposed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250124
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  • 12
    Electronic Resource
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    Alkylchrom- und Alkylmangan-Reagenzien, IV. Über die Aldehyd- und cheleselektive Alkylierung organischer Carbonylverbindungen mit Monoalkylchrom(III)-Reagenzien (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 157-162 
    Details
    ISSN: 0009-2940
    Keywords: Chromium organo compounds ; Chemoselectivity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkylchromium and Alkylmanganese Reagents, IV.  -  On the Aldehyde and Cheleselective Alkylation of Organic Carbonyl Compounds with Monoalkylchromium(III) ReagentsMonoalkylchromium(III) reagents, prepared in crystalline form or in solution, alkylate aldehydes but normally not ketones. Ketones with a basic group (HO, MeO, Me2N) in α- or β-position are methylated by MeCrCl2(thf)3, allowing the highly selective («cheleselective») methylation of such ketones in the presence of normal ketones.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250126
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  • 13
    Electronic Resource
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    Collisionally Activated Dissociation of Some Bulkily Substituted Pyridinium Cations, II. Substituent Effect on Appearance Potential (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 177-181 
    Details
    ISSN: 0009-2940
    Keywords: Gas-phase dissociation ; Appearance energies ; Calculations, AM1 ; Pyridinium cations, N-benzyl-2,4,6-substituted ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Collisionally activated dissociations (CADs) of various pyridine-ring substituted N-benzylpyridinium cations in the gas phase form the substituted pyridine and benzyl carbocation. Appearance energies (AEs) are estimated quantitatively from the appearance thresholds of the corresponding fragment ion from the laser-desorbed pyridinium cations. MO calculations predict that such unimolecular dissociation processes lead initially to ion-molecule pairs (IMPs): some such IMPs are of significantly lower energy than the fully dissociated products. The AEs have also been compared with the energy differences [ΔΔHf=ΔHf(Py) + ΔHf(R+)  -  ΔHf(Py+R)] determined by AM1 calculations: in many cases these are quite close to the calculated energy differences; discrepancies are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250129
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  • 14
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    Zum Mechanismus der Cyclopropan-“Walk”-Umlagerung: Synthese und Eigenschaften eines optisch aktiven Diazoalkan-Addukts von Toluol; eine hochstereoselektive N2-EliminierungHerrn Professor Horst Prinzbach zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 197-208 
    Details
    ISSN: 0009-2940
    Keywords: Azoles, optically active, thermolysis and photolysis of ; Walk rearrangement ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mechanism of the Cyclopropane “Walk” Rearrangement: Synthesis and Properties of an Optically Active Diazoalkane-Toluene Adduct; a Highly Stereoselective N2 EliminationThe synthesis and the thermal and photochemical behavior of the optically active 2-diazo-1-methoxypropane-toluene adduct 3 are reported. The N2 elimination of 3 ocurs with one and the same stereochemical course upon thermolysis as well as direct photolysis: 7-(Methoxymethyl)-1,7-dimethyl-1,3,5-cycloheptatriene (1) is formed with retention of configuration at C-7 and 7-(methoxymethyl)-2,7-dimethyl-1,3,5-cycloheptatriene (2) with inversion of configuration at C-7. These stereochemical findings are explained by an intermediary singlet diradical 1[4] in which the ring closure between C-1 and C-7 or C-5 and C-7 is faster than the rotation around the single bond between C-6 and C-7. In the case of the thermally induced formation of 2 a concerted N2 elimination has to be considered as a competitive pathway. The results presented here are well in accord with the stereochemical analysis of the cyclopropane “walk” rearrangement 1⇋2 reported previously and are therefore a good evidence that the diradical intermediate 4 is also involved in the “walk” rearrangement. In the photochemically induced N2 elimination of 3, sensitized by benzophenone and leading again to 1 and 2, a surprisingly high degree of stereoselectivity is observed. Thus, the intermediary triplet diradical 3[4] must have a much shorter life time than ordinary 1,3-diradicals in the triplet state.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250132
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  • 15
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    Hydrierwärmen, IV. Zur Frage der Homoaromatizität von Norcaradien und Cycloheptatrien (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 217-224 
    Details
    ISSN: 0009-2940
    Keywords: Homoaromaticity ; Resonance energy ; Calculations, force-field ; Heats of hydrogenation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heats of Hydrogenation, IV.  -  Homoaromaticity in Norcaradiene and CycloheptatrieneBy comparison of the heats of hydrogenation of fixed norcaradienes with analogous cyclobutane derivatives and from the difference of experimental heats of formation with values calculated by force-field methods the homoaromatic stabilization of norcaradienes and cycloheptatrienes are calculated and compared with the equilibrium position of the respective valence isomers.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250134
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  • 16
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    Regio- and Diastereoselective Ene Reaction of Triazolinedione with Vinylsilanes (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 243-246 
    Details
    ISSN: 0009-2940
    Keywords: Ene reaction ; Silanes, vinyl- ; Triazolinediones ; Cycloaddition ; Regioselectivity ; Diastereoselectivity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ene reaction of 4-methyl-1,2,4-triazoline-3,5-dione (MTAD) with vinylsilanes 1 has been investigated. In all cases studied, only hydrogen abstraction geminal to the silyl group with formation of triazolidinediones 3 occurred, irrespective of the number and size of the substituents at the double bond. A mechanism with an aziridinium imide as intermediate is proposed to explain the observed regioselectivity and diastereoselectivity. For the former we invoke preferential cleavage of the C-N bond proximate to the silyl substituent on the aziridine ring, for the latter steric repulsion between the adjacent silyl and alkyl group controls the observed E-type stereochemistry. A new synthetic approach to the trisubstituted vinylsilane 1e based on reductive lithiation of the corresponding vinyl sulfide is described.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250138
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  • 17
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    [3.3]Metacyclophane mit anti-Konformation (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 255-258 
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    ISSN: 0009-2940
    Keywords: Cyclophane ; [3.3]Metacyclophane, conformation of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [3.3]Metacyclophanes with anti ConformationThe [3.3]metacyclophanes 5 and 9 with prevailing anti conformation were prepared by using different cyclisation techniques. 1H-NMR studies and X-ray structure analyses of both phanes 5 and 9 prove their unprecedented conformations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250140
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  • 18
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    Organische Synthesen mit Übergangsmetall-Komplexen, 57. 4,5-Homotropilidene durch intramolekulare Cyclopropanierung von (Cycloheptatrienylmethyl)carbenchrom- oder -wolfram-Komplexen (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 259-264 
    Details
    ISSN: 0009-2940
    Keywords: (Cycloheptatrienylmethyl)carbene complexes ; 4,5-Homotropilidenes ; Cyclopropanation, intramolecular ; Carbene complexes ; Cope rearrangement, metal influence on ; Rhodium complexes ; Iron complexes ; Chromium complexes ; Tungsten complexes ; Calculations, AM1, MNDO, PM3 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organic Syntheses via Transition Metal Complexes, 57[1].  -  4,5-Homotropilidenes by Intramolecular Cyclopropanation of (Cycloheptatrienylmethyl)carbenechromium or -tungsten Complexes(Cycloheptatrienylmethyl)carbene complexes LnM=C(OEt)-CH2C7H7 [3: LnM=Cr(CO)5 (a), W(CO)5 (b)] are obtained in yields of 80% by the reaction of the corresponding methylcarbene complexes LnM=C(OEt)CH3 1 with tropylium tetrafluoroborate (2) in THF/Et3N. Alkylation of 3 with 2 gives [bis(cycloheptatrienyl)methyl]carbene complexes LnM=C(OEt)CH(C7H7)2 [4: LnM=Cr(CO)5 (a), W(CO)5 (b)]. Thermolysis of 3 leads to the formation of an equilibrium mixture of the 4,5-homotropilidenes 5 and 6. According to NMR measurements and AM1 calculations the formation of 6 is strongly favored. An equilibrium between 4,5-homotropilidene complexes is significantly different from that of the metal-free ligands. By the reaction of 5/6 with bis(ethylene)rhodium 1,3-pentanedionate (8) the complexes 9 and 10 of both 4,5-homotropilidenes 5 and 6 are obtained in a 1:3 ratio. The (1,5-diene)rhodium(I) complexes 9 and 10 are nonfluxional and configurationally moderately stable at 20°C. The reaction of 5/6 with Fe2(CO)9 gives the π-allyl,σ complexes 11 and 12 in a 10:3 ratio, both of which may be derived from the minor 4,5-homotropilidene isomer 5. In 11 a vinylcyclopropane unit of 5 serves as a four-electron donor for a Fe(CO)3 group. In 12 the 4,5-homotropilidene unit is coordinated as a six-electron donor to a Fe2(CO)6 unit.
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    Über Hans Musso (1925-1988) und sein wissenschaftliches Werk (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. I 
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    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Struktur und Reaktivität von Bis(π-pentamethylcyclopentadienyl)-(2-methyliden)titanacyclobutan (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 291-299 
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    ISSN: 0009-2940
    Keywords: Titanacyclobutane complexes ; Vinylidene intermediates ; Titanium complexes ; MO theory, applied ; Cycloreversion ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure and Reactivity of Bis(π-pentamethylcyclopentadienyl)(2-methylidene)titanacyclobutaneThe reaction of vinyllithium with bis(π-pentamethylcyclopentadienyl)titanium dichloride in a molar ratio of 2:1 quantitatively yields the unexpected titanacyclobutane derivative (2) (Cp* = [C5(CH3)5]). The isolated complex 2 has been characterized by spectroscopic methods and by elemental analysis, and its structure has been confirmed by an X-ray structure determination. The chemical reactivity of 2 is characterized by the splitting of the four-membered ring at higher temperatures, forming a titanocene vinylidene fragment {Cp2*Ti = C = CH2} and ethylene. This cycloreversion is confirmed by the fragmentation behavior in the mass spectrometer, and some aspects of it have been studied by Extended Hückel Model calculations.
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    Ein Dipyrrino-Cryptand  -  Synthese, Kristallstruktur, Metallkomplexierung (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 447-452 
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    ISSN: 0009-2940
    Keywords: Chromoionophore ; Chromoacerand ; Cryptand ; Dipyrrin ; Metal complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Dipyrrino Cryptand  -  Synthesis, Crystal Structure, Metal ComplexationThe orange red cryptand 1, containing a dipyrrin chromophore, has been synthesized in seven steps. Its C2-symmetrical X-ray structure exhibits a planar dipyrrin unit and a twisted but not collapsed crown ring, two of the ether oxygen atoms projecting outwards. The complexation of alkali and transition metal cations by this concave dyestuff leads to changes of the color and to strong shifts in the UV/Vis spectra.
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    URL: http://dx.doi.org/10.1002/cber.19921250223
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    Synthesis of a Novel Optically Active C2-Symmetric 2,2′-Bipyridine (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 453-458 
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    ISSN: 0009-2940
    Keywords: 2,2′-Bipyridine ; Chiral ligand ; Palladium complexes ; Copper complexes ; Cobalt complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically active 2,2′-bipyridine (S,S)-1 was synthesized by radical cyclization and a nickel(0)-mediated coupling of enantiomerically pure bromopyridine (S)-8. Palladium, copper, and cobalt complexes of 1 were prepared. The solid-state structures of meso-1 and 11 were determined by X-ray crystal structure analysis.
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    Zum Kenntnisstand der 1,3,5-Triaza-2,4-diphospha-1,4-pentadieneHerrn Professor Heinrich Puff zum 70. Geburtstag gewidmet (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 321-330 
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    ISSN: 0009-2940
    Keywords: Phosphanes, (Z)-amino(imino)- ; 1,3,5-Triaza-2,4-diphospha-1,4-pentadienes, transition metal complexes of, dynamic behavior of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Knowledge of the 1,3,5-Triaza-2,4-diphospha-1,4-pentadienesHerrn Professor Heinrich Puff zum 70. Geburtstag gewidmetNucleophilic substitution reactions of the chloro(arylimino)-phosphane 1 yield the NH-functional amino(imino)phosphanes Mes*NPNHR (R = Mes, Ad, CPh3) 2d - f. Upon further reaction with 1 they are converted into the 1,3,5-triaza-2,4-diphospha-1,4-pentadienes Mes*NPN(R)PNMes* (R = Mes, Ad) 4d, e and Mes*NPN(Mes*)PNCPh3 5. According to crystal structure determinations all compounds 4a, d, e, 5 exhibit S conformation in the solid state. In addition to the “exo-endo” arrangement of the substituents (4a, 5) in the case of 4d, e the “endo-endo” conformation is observed for the first time. In solution, 4d, e and 5 are subject to dynamic rearrangements, whose mechanism is proven by NMR studies of partially 15N-enriched samples. The reaction of 4a with NorM(CO)4 (M = Cr, Mo) or Ni(CO)4 yields the metallaazadiphosphetidine complexes 6a - c Mes*NPN(tBu)PNMes*M(CO)n [M(CO)n = Cr(CO)4, Mo(CO)4, Ni(CO)2]. The crystal structure of 6a (“exo-endo-W”) is described.
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    Bis(cyclopentadienyl)methan-verbrückte Zweikernkomplexe, IV. Synthese, Struktur und Reaktivität von Zweikernkomplexen des Rhodiums und Iridiums in der Oxidationsstufe +I und +III mit dem Bis(cyclopentadienyl)methan-Dianion als Brückenliganden (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 337-346 
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    ISSN: 0009-2940
    Keywords: Dinuclear rhodium and iridium complexes ; Bis(cyclopentadienyl)methane dianion as bridging ligand ; Substitution and bridge-splitting reactions ; Rhodium complexes ; Iridium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(cyclopentadienyl)methane-Bridged Dinuclear Complexes, IV[1].  -  Synthesis, Structure, and Reactivity of Dinuclear Rhodium and Iridium Complexes in the Oxidation State +I and +III with the Bis(cyclopentadienyl)methane Dianion as Bridging LigandThe rhodium compounds [CH2(C5H4)2][Rh(L)(C2H4)]2 (2, 4) were prepared from [RhCl(L)(C2H4)]2 (1, 3) and CH2(C5H4)2Li2 in 92 and 73% yield, respectively. The reaction of 4 with Cl2, Br2, and I2 led to the almost quantitative formation of the dihalogeno derivatives [CH2(C5H4)2][RhX2(PiPr3)]2 (6-8), which on treatment with excess NaBH4 and methanol gave the dihydride [CH2(C5H4)2][RhH2(PiPr3)]2 (10). From [RhCl(C8H14)2]2 (12), PiPr3, and CH2(C5H5)2 the chloro(hydrido)rhodium complex [CH2(C5H4)2][RhH(Cl)(PiPr3)]2 (13) was obtained. Protonation of 10 with CF3CO2H in the presence of NH4PF6 gave the PF6 salt of the hydrido-bridged cation {[CH2(C5H4)2]-[RhH(PiPr3)]2(μ-H)}+ (14) of which the crystal structure was determined. In solution, fluxional behavior of the cation was observed. The dimethyl compound [CH2(C5H4)2][Rh(CH3)2-(PiPr3)]2 (17), prepared from 6, 7, or 8 and LiCH3 or CH3MgI in 80% yield, reacted with CF3CO2H at  -  78° C to give the tri-fluoroacetato derivative 18; this on treatment with P(OMe)3 and dmpe formed the dicationic complexes 19 and 20, respectively. The dinuclear iridium compounds [CH2(C5H4)2]-[Ir(olefin)2]2 (26, 27) and [CH2(C5H4)2][Ir(C8H12)]2 (28) were prepared from [IrCl(L)2]2 (23-25) and CH2(C5H4)2Li2 and used for the synthesis of {[CH2(C5H4)2][IrX2]2}n (29, 30). Compounds 29 and 30 served as starting materials for the preparation of the dinuclear derivatives [CH2(C5H4)2][IrX2(L)]2 (31-34) and {[CH2(C5H4)2][IrBr2]2(μ-dipy)} (35) and finally also for the dihydrido complex [CH2(C5H4)2][IrH2(PiPr3)]2 (36).
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    Bis(di-tert-butylphosphanyl)methan-Komplexe des Rhodiums: Geometrie, Elektronenstruktur und Derivate des 14-Elektronenteilchens [Rh(dtbpm)Cl]. Molekülstruktur von Rh(dtbpm)Cl(PMe3) (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 353-365 
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    ISSN: 0009-2940
    Keywords: Rhodium(I) phosphane complexes ; 14-Electron intermediates ; MO theory, applied ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(di-tert-butylphosphanyl)methane Complexes of Rhodium: Geometry, Electronic Structure, and Derivatives of the 14-Electron Fragment [Rh(dtbpm)Cl]. Molecular Structure of Rh(dtbpm)Cl(PMe3)14-Electron fragments [M(PR3)2X] (M = Rh, Ir, X = halogen etc.) are considered to be an important class of highly reactive, coordinatively unsaturated intermediates in many metal-induced stoichiometric or catalytic transformations of organic substrates. As available theoretical data suggest a slightly preferred T-shaped groundstate geometry with a less symmetric cis rather than the usually implied trans phosphane arrangement for such tricoordinate d8-ML3-type systems with monodentate phosphanes PR3, the chemistry of η2-diphosphanylmethane complexes of rhodium with four-membered RhPCP-chelate rings and thus with enforced cis phosphane coordination and anomalously small cis P - Rh - P angles has been studied by theory and by experiment. MO calculations (EH) have been performed both for the model 14-electron system [Rh(dhpm)Cl] (dhpm = diphosphanylmethane, H2P - CH2 - PH2) and for the experimentally accessible fragment [Rh(dhbpm)Cl], where dtbpm is bis(di-tert-butylphosphanyl)-methane, (tBu)2P - CH2 - P(tBu)2. The electronic and geometric structure of these species is described. Employing the unusual ligand dtbpm, tailor-made for stabilizing mononuclear η2- and destabilizing dinuclear μ-diphosphanylmethane coordination, the chloro-bridged dimer [Rh(dtbpm)Cl]2, has been synthesized. In agreement with steric and electronic considerations, its chemistry is dominated by a facile dissociation to monomeric (presumably solvent coordinated) fragments [Rh(dtbpm)Cl], even in benzene, as suggested by molecular mass determinations. Accordingly, by using [Rh(dtbpm)Cl]2 as a starting material, a series of sterically very congested but nevertheless mononuclear, square-planar complexes Rh(dtbpm)Cl(L) (L = CO, PMe3, PPh3, PCy3, pyridine, acrylonitrile) with chelating dtbpm could be readily prepared and fully characterized. The relative stability of these potential alternative precursors of a [Rh(dtbpm)Cl] intermediate towards dissociation of ligands L is reported. The molecular structure of Rh(dtbpm)Cl(PMe3) as the first representative of this class of compounds has been determined by X-ray crystallography.
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    Synthese und Struktur von Bis(trimethylstannyl)- und Bis(dimethylhalogenstannyl)aminen: zur Rolle des Stickstoff-Elektronenpaares (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 389-400 
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    ISSN: 0009-2940
    Keywords: Amines, bis(trimethylstannyl)organyl-, bis(dimethylhalostannyl)organyl- ; Bond cleavage, SnN ; 1,3,2,4-Diazadistannetidine, hexamethyl- ; N.N′-Bis(dichlorodimethylstannane) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Structure of Bis(trimethylstannyl) and Bis(dimethylhalostannyl) Amines: The Role of the Nitrogen Lone PairMonoaminostannanes RNH -  SnMe3 (1) with substituents R = tBu, Mes, 2,6-iPr2C6H3 are obtained by transmetallation from Me3SnX and RNH - Li, the distannylamines RN(SnMe3)2 (2) by transamination of Et2N  - SnMe3 with RNH2, and bis(dimethylhalostannyl)amines R - N(SnMe2X)2 (8) by stannazane cleavage of 2 with Me2SnX2 or by SnC cleavage with BX3 (8n, o). Me2Sn(NtBuH)2, prepared from tBuNHLi and Me2SnBr2, decomposes with tBuNH2 elimination into the diazadistannetidine 4 already below room temperature. Information from multinuclear NMR spectra of type 2, 4, and 8 compounds ascertain the proposed relation between the value of the geminal coupling constant 2J(119Sn117Sn) of distannazanes and the Sn - N - Sn bond angle as determined by the X-ray structure analysis of 2c and of (8a)2 as well as the participation of the electron pair at the nitrogen atom in bonding. 2c has C2 symmetry, contains a planar nitrogen atom with SnN bond lengths of 2.044 Å and an Sn - N - Sn bond angle of 125.0°. The aryl group stands perpendicular to the Sn2N plane. These data exclude any π interaction between the N atom and the substituents. 2c, therefore, represents an example of a tertiary amine with the lone electron pair at the nitrogen atom in a p-type orbital. The supposed distannylamine (ClMe2Sn)2NMe (8a) is actually a dimer, whose unexpected structure contains a diazadistannetidine unit bearing two Me2SnCl2 groups at its nitrogen atoms in cis-configuration. This arrangement allows the formation of weak intramolecular SnCl bonds.
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    Strukturaufklärung eines doppelsträngigen Polymers mittels Modellstudien (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 433-445 
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    ISSN: 0009-2940
    Keywords: Poly Diels-Alder reactions ; Molecules, double-stranded ; Configuration of double-stranded molecules ; Ladder polymers, spherical shape ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure Elucidation of a Double-Stranded Polymer by Using Model StudiesSyntheses and complete structural characterization (including constitution, configuration, conformation) of the double-stranded compounds Ua-5b, Ss-5b, U-7b, S-7b, UUa-8, SUs-8, UUUaa-9, USUas-9, SUUsa-9, and SSuss-9 are described. These compounds contain up to three repeating units of the ladder polymer 3 and are therefore used as model compounds to elucidate interesting structural aspects of this polymer. A model for the spherical shape of 3 is presented. The molecular structures in the crystals of S-7b, SUs-8, Ua-5b have been determined.
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    Synthesis, Fluorescence, and Photostabilities of 3-(Perfluoroalkyl)coumarins (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 467-471 
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    ISSN: 0009-2940
    Keywords: Bis(perfluoroalkanoyl) peroxides ; Coumarins, 3-perfluoroalkyl ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The regioselective reaction of coumarins 1 with bis(perfluo-roalkanoyl) peroxides affords 3-(perfluoroalkyl)coumarins 2 in moderate yields. The absorption and emission maxima of coumarins 2 show bathochromic shifts compared with the 3-unsubstituted coumarins. The fluorescence intensities of 3-(perfluoroalkyl)coumarins 2 are smaller than those of the 3-unsubstituted ones. However, the photostabilities of coumarins 2 are higher than those of the 3-unsubstituted ones.
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    Asymmetrische Katalysen, 77[1] Neue optisch aktive Pyrazolderivate für die enantioselektive Katalyse (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 701-709 
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    ISSN: 0009-2940
    Keywords: Pyrazoles, optically active ; Pyridines, 2-[3(5)-pyrazolyl]-, 2,6-bis[3(5)-pyrazolyl]-, 2-(1-pyrazolyl)- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Asymmetric Catalysis, 77[1]. - New Optically Active Pyrazole Derivatives for Enantioselective CatalysisStarting from the amines 3-6 and the dipyrazolopyrazinedione 2, the optically active (pyrazolylmethyl)amines 11-14 have been synthesized. Furthermore, the preparation of the (+)-camphor-derived optically active pyrazole 17 is described. Pyrazoles 11-13 and 17 are introduced as chiral building blocks into the 2-(1-pyrazolyl)pyridines 30-33. The optically active compounds 23-25 are formed from 2-[3(5)-pyrazolyl]pyridine and 2,6-bis[3(5-)pyrazolyl]pyridine, respectively, and (+)-3-(bromomethyl)pinane. The pyrazole derivatives 27-29 contain (+)-(1-phenylethyl)hydrazine as the optically active component.
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    Organophosphorverbindungen, 53[1] Cyclopropenyliden-methylen-diphosphane - neue gekreuzt konjugierte Phosphapolyene[2] (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 729-732 
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    ISSN: 0009-2940
    Keywords: Phosphaalkenes ; Phosphatriafulvenes ; Cross-conjugated phosphapolyenes ; Diphosphanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organophosphorus Compounds, 53[1]. - Cyclopropenylidene-methylene-diphosphanes - New Cross-Conjugated Phosphapolyenes[2]The reaction of chloromethylenephosphanes 7 with the inverse cyclopropenylidenephosphanes 6, 10 leads to the formation of the title compounds 8 and 11 as a new class of cross-conjugated phosphapolyenes. The structure of compound 8a has been confirmed by an X-ray structural analysis.
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    Reductive Transformations, 16[1] Electron Transfer and Regioselectivity in the Alkylation of a Hydrocarbon Mono- and Dianion (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 505-513 
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    ISSN: 0009-2940
    Keywords: Carbanion alkylation ; Electron transfer ; Cyclic voltammetry ; Rate constants ; Circular dichroism ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reductive alkylation of the pyrene isomer 1 affords bridged [14]annulenes (2) and 2a,3-dihydro-2a,3-dialkyldicyclopenta[ef,kl]heptalenes (3). The involvement of an electron transfer (ET) in this reaction is demonstrated by optically pure electrophiles. Supporting evidence for ET processes is provided by cyclic voltammetric measurement of rate constants for both the ET process and the SN2 reaction. The choice of the electrophile is relevant not only for the importance of electron transfer, but also for the regioselectivity of the alkylation reaction.
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    η1-P- und η2-OP-gebundene (Ether-phosphan)osmium(II)-Komplexe und ihre gegenseitige Umwandlung (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 541-550 
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    ISSN: 0009-2940
    Keywords: Ether phosphanes ; Osmium(II) complexes ; Conversion ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: η1-P- and η2-OP-Bonded (Ether-Phosphane)Osmium(II) Complexes and their Mutual ConversionReactions of cis-Br2Os(CO)4 with the (ether-phosphane) ligands 2a-f results in the formation of the cis,cis,trans-complexes Br2Os(CO)2(P ∼ O)2 (3a-f). 3b crystallizes in the mono-clinic space group P21/c with Z = 4. Irradiation of 3a-f leads to the cleavage of a further CO group and the formation of an Os—O bond to give the mono(chelate) complexes Br2Os(CO)-(PO) PO (5a-f), with one of the O,P ligands being bidentate. 5a-f exist as mixtures of different trans-P (A,B) and cis-P isomers (C-G). Dependent on the fact that a reversible cis/trans equilibrium or an irreversible trans → cis transformation is possible or that no trans-P isomers are present at any temperature, 5a-f may be classified in three categories. Inter-conversion of the isomers A-G results from dissociation of the η1-P coordinated ether-phosphane and concomitant occurrence of the 16e- species Br2Os(CO)(PO) (8). From temperature-dependent 31P{1H}-NMR spectroscopic investigations the temperature for the reversible opening of the metal-oxygen contact is determined. The reversible opening leads to the complexes Br2Os(CO)(PO)2 (9) with a vacant coordination site depending on the Os-O bonding strength. 5a-f react with CO to give all-trans-Br2Os(CO)2(PO)2 (4a-f). The action of the ether-phosphanes 2a-f on OsBr2(PPh3)4 (7) affords the bis(chelate) complexes Br2Os(PO)2 (6a-f) which add carbon monoxide to form all-trans-4a-f.
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    „2,2′-Bisdimedonyliden” - ein neues elektrophiles OlefinHerrn Professor Klaus Brodersen zum 65. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 675-677 
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    ISSN: 0009-2940
    Keywords: 2,2′-Bisdimedonylidene, synthesis and electrophilic reactions of ; Olefin, electrophilic ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: „2,2′-Bisdimedonylidene‘ - a Novel Electrophilic OlefinHerrn Professor Michael Hanack zum 60. Geburtstag gewidmet.The title compound has been prepared unambiguously by dehydrogenation of known „2,2′-bisdimedonyl’ (8). Its typical electrophilic character leads to additions of various nucleophiles which prove the molecular structure. Physical data are in disagreement with those mentioned in the literature.
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    Kationische Umlagerungen bei 2-Azabicyclo[3.2.0]heptan-Systemen Zur NMR-Analytik von 17O- oder 18O-markierten Substanzen (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 691-700 
    Details
    ISSN: 0009-2940
    Keywords: Cationic rearrangements ; Nitrenium ions ; Ion pairs ; Regio- and stereoselectivity ; NMR, 17O ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cationic Rearrangements of 2-Azabicyclo[3.2.0]heptane Systems. - NMR and MS Methods for the Analysis of 17O- or 18O-Labelled CompoundsO-Tosylation of 2-hydroxy-2-azabicyclo[3.2.0]hept-6-ene and -heptane results in rearrangements to 1-aza-[2.2.1] systems. The regioselectivity is caused by kinetic control. High stereose-lectivity, partial scrambling of the O-label and low yields in cross-over experiments agree with the intermediacy of tight ion pairs. - For the quantitative analysis of labelling, 17O-NMR, 13C-NMR and mass spectrometry are optimized and their efficiencies compared.
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    1,8-Bis(diphenylamino)- and 1,8-Bis(methylphenylamino)naphthalene: Molecular Structure and Dynamic Behavior (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 723-728 
    Details
    ISSN: 0009-2940
    Keywords: 1,8-Diaminonaphthalenes, X-ray structure analysis of, conformational barriers of, dynamic behavior of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compounds 2 and 3 have been synthesized from 1,8-diaminonaphthalene. The molecular structure of 2 has been determined by X-ray structure analysis and is discussed with regard to the arrangement of the peri-diphenylamino substituents in the crystalline state and the steric strain in the molecule. NMR studies of 3 reveal two conformational processes. Their nature is discussed and barriers are reported.
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    Nichtkonzertierte Cope-Umlagerung? 1,2,6,7-Cyclodecatetraen-Thermolyse (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 739-749 
    Details
    ISSN: 0009-2940
    Keywords: Cope rearrangement ; Diradicals ; Oxygen trapping ; Energy well ; Chemical activation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nonconcerted Cope-Rearrangement? 1,2,6,7-Cyclodecatetraene ThermolysisFrom the pressure and oxygen dependence of the trapping rate a two-step mechanism for the Cope rearrangement of the title compound is deduced, its energy profile established, and the heat of formation of the intermediate diradical 3 determined. In contrast to the meso compound the rearrangement of the rac isomer proceeds by two competing processes, a concerted and a nonconcerted pathway. The different behavior of the meso and rac compound can be correlated to the boat and chair geometry of the respective transition states.
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    URL: http://dx.doi.org/10.1002/cber.19921250330
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    Stereoelectronic and Steric Effects in the Synthesis and Recognition of Diastereomeric Ethers by NMR and EPR SpectroscopyHerrn Professor Ernst Buyer zum 65. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 857-865 
    Details
    ISSN: 0009-2940
    Keywords: Quinone methides ; Stereoelectronic effects ; Chiral recognition ; EPR ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (2,6-Di-tert-butyl-4-hydroxyphenyl)-alkyl-carbinols I are easily dehydrated in the presence of catalytic amounts of a mineral acid to form the corresponding phenyl-alkyl-carbocations Ia. These cations can be reversibly deprotonated to the quinone methides Ib, therefore, an equilibrium between both reactive compounds is assumed. In the absence of nucleophiles a reaction of these intermediates with the starting carbinol is observed leading to symmetrical ethers Id. In alcoholic solution the solvent acts as a nucleophilic compound and the formation of an unsymmetrical ether Ie is observed predominantly. If the nucleophile contains a chiral carbon atom diastereomers are formed in this reaction which are observed in variable concentrations depending on the reaction time. The assignment of these isomers to the meso and racemic compound has been achieved by NMR investigations in solution in combination with their solid-state structures determined by X-ray crystallography. These results indicate a remarkable thermodynamic stabilization of the symmetrical ethers in the racemic form whereas the meso compounds are favored if the products are formed under kinetic control. In both cases the diastereomer ratio is determined by steric repulsion and the generalized anomeric effect. - A bonding interaction of lone pairs of the ether oxygen with the π system of the corresponding phenoxyl ring was also observed by EPR investigations. This electron delocalization contributes remarkably to the mechanism responsible for the distinction of the diastereomeric radicals by different β-proton coupling constants.
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    Alkyleisen- und Alkylcobalt-Reagenzien, IV[1] Aldehydselektive Cyanoalkylierungen mit Cyanoalkyl-Derivaten von Eisen(II) und anderen Übergangsmetallen (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 899-905 
    Details
    ISSN: 0009-2940
    Keywords: Organoiron compounds ; Iron(II) alkyls ; Cyanoalkylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkyliron and Alkylcobalt Reagents, IV[1]. - Aldehyde-Selective Cyanoalkylation with Cyanoalkyl Derivatives of Iron(II) and Other Transition MetalsFor the transfer of the cyanomethyl residue with high aldehyde vs. ketone selectivity, the Fe reagent 3 a is a good alternative to the known Ti reagent 1a[2], whereas analogous reagents with the metals Mn, Co, Ni or Cu are unfavorable. For the aldehyde- vs. ketone-selective transfer of the branched residues 1-cyanoethyl and cyanoisopropyl, the Fe reagents 3b and 3c are distinctly better than the Ti reagents 1b and 1c.
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    Remarkable Effect of Fluorine and Chlorine Atoms on the Stability of 1H-Phosphirene (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 923-927 
    Details
    ISSN: 0009-2940
    Keywords: 1H-Phosphirenes ; 2H-Phosphirenes ; Calculations, ab initio ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio MO calculations at the MP4/6-31G** level show that both fluorine and chlorine atoms exert a strong stabilizing effect on the three-membered ring 1H-phosphirene relative to its isomers. While unsubstituted 1H-phosphirene (12H) is the least stable C2H3P isomer, 1-fluoro-1H-phosphirene (12F) is calculated to be the global minimum of the C2H2FP potential energy surface; 1-chloro-1H-phosphirene (12Cl) is the third most stable of the six C2H2ClP isomers calculated. The remarkable stability of 12F is attributable to the particular strength of the P - F bond.
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    Stereoselektivität von Photocycloadditionen, 5[1] Photoreaktionen zwischen 2-Cyclopenten-1-on und Enolethern (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 933-940 
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    ISSN: 0009-2940
    Keywords: [2 + 2] Photocycloaddition ; Selectivity, stereo-, regio- ; 1,4-Biradicals ; INADEQUATE ; Calculations, AM1, FINITE ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stereoselectivity in Photocycloaddition Reactions, 5[1]. - Photoreaction of 2-Cyclopenten-1-one with Enol EthersThe regio- and stereoselectivity of [2 + 2] photocycloaddition reactions between 2-cyclopenten-1-one (1) and the electron-rich alkenes: ethyl, isopropyl, and phenyl vinyl ether (2-4) as well as 2,3-dihydrofuran (10) were examined. In all cases the annulated cyclobutene derivatives 5-7 and 11 were isolated in yields between 70 and 99%. The regioisomeric HT/HH products were formed in a ratio of 3:1 to 4:1. For the determination of the product stereochemistry, INADEQUATE and 1H,1-decoupling experiments were performed. Computer-assisted investigations on the molecular geometry and 1H,1H-coupling constants were performed by using semiempirical methods (AM1, FINITE). The HT regioisomers were formed with moderate endo diastereoselectivity, whereas in the case of the HH regioisomers both diastereomers (exo/endo) were formed in equal amounts. Photoreaction with 2,3-dihydrofuran (10) led to almost exclusive formation of exo-diastereomeric HH and HT regioisomers 11. The observed stereoselectivity is rationalized by the optimal geometry of the intermediate triplet 1,4-biradicals during intersystem crossing.
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    Chiral Organometallic Reagents, V[1] A Test on the Configurational Stability of Chiral Organolithium Compounds Based on Kinetic Resolution; Scope and Limitations (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 975-982 
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    ISSN: 0009-2940
    Keywords: Configurational stability ; Kinetic resolution ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The test on the configurational stability of chiral organolithium compounds is based on the kinetic resolution of the racemic organolithium compound on reaction with an enantiomerically pure electrophile. The limits of this test have been evaluated by model calculations. The factors that have been considered are: Optimum values for the kinetic resolution; effects of 〈 100% enantiomeric purity of the chiral electrophile; parallel side reactions of the organolithium compounds with the electrophile.
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    Masthead (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cber.19921250501
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    Metallkomplexe in Anorganischen Matrices, 8[1] Chromtricarbonyl-Komplexe von Benzoylacetonat-substituierten Titan-, Zirkonium- und Aluminium-AlkoxidenHerrn Professor Wolfgang Beck zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 999-1003 
    Details
    ISSN: 0009-2940
    Keywords: β-Diketonates ; Metal alkoxides ; Sol-gel chemistry ; π-Arene complexes ; Chromium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal Complexes in Inorganic Matrices, 8[1]. - Chromium Tricarbonyl Complexes of Benzoylacetonate-Substituted Titanium-, Zirconium-, and Aluminium Alkoxides*Benzoylacetone (bzac-H) reacts with one equivalent of Al(OtBu)3 or Zr(OPr)4 to give the mono-substituted compounds (bzac)Al(OtBu)2 (1b) and (bzac)Zr(OPr)3 (1a), while with one equivalent of Ti(OtBu)4 or Zr(OtBu)4 the bis-substituted derivatives (bzac)2Ti(OtBu)2 (3c) and (bzac)2Zr(OtBu)2 (3d) are obtained. Upon heating in dibutyl ether, 1b disproportionates into (bzac)2Al(OtBu) (3b) and Al(OtBu)3. Thermal reaction of 1a, 3b, and 3c with Cr(CO)6 leads to metal complexes having a Cr(CO)3 moiety π-bonded to the phenyl group of the benzoylacetonate ligand.
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    Bis(cyclopentadienyl)methan-verbrückte Zweikernkomplexe, V. Heteronukleare Co/Rh-, Co/Ir-, Rh/Ir- und Ti/Ir-Komplexe mit dem Bis(cyclopentadienyl)methan-Dianion als BrückenligandenHerrn Professor Wolfgang Beck zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1017-1022 
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    ISSN: 0009-2940
    Keywords: Cyclopentadienyl anion, substituted ; Cobalt complexes ; Rhodium complexes ; Iridium complexes ; Bis(cyclopentadienyl)methane dianion as bridging ligand ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(cyclopentadienyl)methane-bridged Dinuclear Complexes, V[1]. - Heteronuclear Co/Rh-, Co/Ir-, Rh/Ir-, and Ti/Ir Complexes with the Bis(cyclopentadienyl)methane Dianion as Bridging Ligand*The lithium and sodium salts of the [C5H5CH2C5H4]- anion, 1 and 2, react with [Co(CO)4I], [Rh(CO)2Cl]2, and [Ir(CO)3Cl]n to give predominantly the mononuclear complexes [(C5H5-CH2C5H4)M(CO)2] (3, 5, 7) together with small amounts of the dinuclear compounds [CH2(C5H4)2][M(CO)2]2 (4, 6, 8). The 1H- and 13C-NMR spectra of 3, 5, and 7 prove that the CH2C5H5 substituent is linked to the π-bonded ring in two isomeric forms. Metalation of 5 and 7 with nBuLi affords the lithiated derivatives 9 and 10 from which on reaction with [Co(CO)4I], [Rh(CO)2Cl]2, and [C5H5TiCl3] the heteronuclear complexes [CH2(C5H4)2][M(CO)2][M′(CO)2] (11-13) and [CH2(C5H4)2]-[Ir(CO)2][C5H5TiCl2] (17) are obtained. Photolysis of 11 and 12 leads almost quantitatively to the formation of the CO-bridged compounds [CH2(C5H4)2][M(CO)(μ-CO)M′(CO)] (14, 15). According to an X-ray crystal structure analysis the Co/Rh complex 14 is isostructural to [CH2(C5H4)2][Rh2(CO)2(μ-CO)] (16).
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    Alkoxygermanate(II), -stannate(II) und -plumbate(II) zweiwertiger Metall-Ionen, II. Verbindungen des Formeltyps M2El2(OtBu)8 (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1033-1042 
    Details
    ISSN: 0009-2940
    Keywords: Germanium compounds ; Tin compounds ; Lead compounds ; Transition-metal complexes ; Paramagnetism ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkoxygermanates(II), -stannates(II), and -plumbates(II) of Divalent Metal Ions, II[1]. - Compounds of the Formula M2El2(OtBu)8By simple salt-exchange processes the starting materials Na2El2(OtBu)6 (El = Ge, Sn, Pb) can be transformed to germanates, stannates and plumbates of divalent magnesium and divalent transition metals. Two types of compounds are formed in these reactions: MEl2(OtBu)6 [El = Ge, M = Mg (1A), Cr (1B), Mn (1C), Zn (1F); El = Pb, M = Mn (3C), M = Zn (3F)] and M2El2(OtBu)8 [El = Ge, M = Co (1d), Ni (1e); El = Sn, M = Mg (2a), Cr (2b), Mn (2c), Co (2d), Ni (2e); El = Pb, M = Co (3d)]. Single-crystal X-ray diffraction studies have been performed on 1C, 1d, 2a, 2b, 2c, 2d, and 2e, and the structures have been solved. In 1C the Mn atom occupies the center of an elongated O6 octahedron, the germanium(II) atoms displaying pyramidal coordination by three oxygen atoms. The central molecular cage can be described as two MnO3Ge trigonal bipyramids sharing the common central Mn atom and being wrapped by tert-butyl groups linked to the oxygen atoms. The other compounds of the MEl2(OtBu)6 formula seem to be isostructural with the exception of 3F, which displays a 1H-NMR spectrum which is not compatible with this structure. All X-ray structures of the compounds M2El2(OtBu)8 show the same feature: to a central M2(OtBu)2 four-membered ring are spirocyclically connected two M(OtBu)2El rings through the common metal atoms M. The structure is completed by the coordination of an exocyclic tert-butoxy group to the terminal El atoms. The metal atoms M are therefore quasi tetrahedrally coordinated while the Ge and Sn atoms are in pyramidal threefold oxygen atom environments. All molecules display an El⃛M⃛M⃛El one-dimensional arrangement. From susceptibility measurements it is apparent, that in the compounds MEl2(OtBu)6 and M2El2(OtBu)8 the transition metal atoms are in high-spin configurations, which is also supported by the UV spectra. Analysis of the structural data of the series 2a-2e reveal important contributions of the electronic environments of the transition metal atoms to the M⃛M and M⃛Sn distances. A qualitative MO description is used to explain these features. Again it has been shown that the, „geometrical softness“ of Ge(OtBu)3 and Pb(OtBu)3 is greater than of Sn(OtBu)3, as the former two can accomodate Cr2+ and Mn2+ in a sixfold coordination site by two units, while Sn(OtBu)3 coordinates Cr2+ and Mn2+ with only two alkoxy groups. When 1C and 2d are allowed to react with nonacarbonyldiiron Mn-Ge2(OtBu)6 · 2 Fe(CO)4 (4) and Co2Sn2(OtBu)8 · 2 Fe(CO)4 (5), respectively, are formed. Compound 4 displays presumably five metal atoms in a linear arrangement while 5 has six metallic elements arranged in one dimension. The latter fact has been unambigously proved by an X-ray structure determination.
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    Enantioselektive Katalyse, VIII. Neue 1,2-Bisphosphanliganden mit vier stereogenen Zentren und zusätzlichen Methoxygruppen für die asymmetrische katalytische HydrierungHerrn Professor Wolfgang Beck zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1061-1072 
    Details
    ISSN: 0009-2940
    Keywords: 3,4-Bis(phosphanyl)pyrrolidines ; Palladium complexes ; Rhodium complexes ; Asymmetric hydrogenation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantioselective Catalysis, VIII[1]. - New 1,2-Bisphosphane Ligands with Four Stereogenic Centers and Additional Methoxy Groups for Asymmetric Catalytic Hydrogenation*The synthesis of N-acyl derivatives of all possible diastereomers of [P(R,S), 3R, 4R,P′(R,S)]-3,4-bis[(benzyl)phenylphosphanyl]-pyrrolidine and [P(R,S), 3R, 4R,P′(R,S)]-3,4-bis[(2-methoxybenzyl)phenylphosphanyl]pyrrolidine in optical pure form is described. Palladium and rhodium complexes with these ligands were prepared. The enantioselective hydrogenation of acetamidocinnamic acid with these rhodium complexes was studied at H2 pressures between 1 and 75 bar. There is only a small influence of the 2-methoxy group in the ligand on the catalytic hydrogenation when compared with the respective unsubstituted diastereomer. The structure of {[PR,3R, 4R,P′R)-1-(tert-butoxycarbonyl)-3,4-bis[(2-methoxybenzyl)phenylphosphanyl]pyrrolidine-P,P′}diiodopalladium was determined by X-ray diffraction.
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    Übergangsmetallkomplexe von Diazenen, XXX. Zur Photoreaktion von Octacarbonyl-dimetallaheterocyclen mit Bis(phosphanen)Herrn Professor Dr. Wolfgang Beck zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1083-1086 
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    ISSN: 0009-2940
    Keywords: Dichromium carbonyls ; Diazirine complexes ; Dimetallaheterocycles ; Photosubstitution ; Bis(phosphanes) ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition Metal Complexes of Diazenes, XXX[1]. - On the Photoreaction of Octacarbonyl Dimetallaheterocycles with Bis(phosphanes)*Irradiation of (CO)4Cr(μ-pmd)2Cr(CO)4 (1) (pmd = 3,3-penta-methylenediazirine) in the presence of bis(dimethylphosphanyl)methane (dppm) affords (CO)3(μ-pmd)2(μ-dppm)Cr(CO)3 (2b) and (CO)4Cr(μ-pmd)(μ-dppm)Cr(CO)4 (3b) which both contain boat-like dimetallaheterocyclic rings as indicated by X-ray analysis. Contrary to that, in the presence of cis-1,2-bis(diphenylphosphanyl)ethene the reaction affords the known Cr(CO)4(cdpe) (4c) by complete cleavage of the dimetalla-heterocycle.
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    Isocyanid- und Heteroallen-verbrückte Metallkomplexe, X. Protonierung und Alkylierung von (μ-Acylisocyanid)- und (μ-Iminoacylisocyanid)dieisen-Komplexen (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1101-1105 
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    ISSN: 0009-2940
    Keywords: Iron complexes, dinuclear ; Bridging functional isocyanides ; N-Protonation (alkylation) ; μ-Aminocarbyne ; μ-2-Azaallyl vs. μ-2-azaallenium ligand ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isocyanide- and Heteroallene-Bridged Metal Complexes, X[1,2]. - Protonation and Alkylation of (μ-Acylisocyanide)- and (μ-Iminoacylisocyanide)diiron ComplexesProtonation of the acyl isocyanide-bridged diiron complexes cis-[Fe2Cp2(CO)3(μ-CNCOR)] [R = Ph (1a); C6H4NO2-(4) (1b)] with HBF4 or HPF6 occurs at the isocyano nitrogen to give the cationic μ-aminocarbyne complexes 2a and 2b, respectively. In contrast, the μ-iminoacyl isocyanide complex 3 is both protonated and alkylated at the imino nitrogen. According to an X-ray structure analysis of 4a, the resulting ligand systems in cis-[Fe2Cp2(CO)3{μ-CNC(Ph)N(Ph)R}]+BF4+ [R = H (4a); Et (4b)] are best described as hybrids of μ-2-azaallylidene-and μ-2-azaallenylidene-type resonance structures.
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    Zum Mechanismus der Carbodesilylierung 4- bzw. 5-substituierter 2-(Trimethylsilyl)pyridine mit Benzaldehyd (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1131-1140 
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    ISSN: 0009-2940
    Keywords: Pyridines, substituted 2-(trimethylsilyl)-, synthesis of, carbodesilylation of ; Carbodesilylation ; Rate constants ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Mechanism of the Carbodesilylation of 4- or 5-Substituted 2-(Trimethylsilyl)pyridinesAn “ylide mechanism” is proposed for the carbodesilylation of 2-(trimethylsilyl)pyridines with benzaldehyde. In contrast, 3-and 4-(trimethylsilyl)pyridines, react only in the presence of a base catalyst via pyridyl anions with electrophiles. The rates of the uncatalyzed carbodesilylation reactions of 4-substituted 2-(trimethylsilyl)pyridines 2 with benzaldehyde correlate very well with the resonance parameters of the substituents ρRO, whereas the rates of 5-substituted 2-(trimethylsilyl)pyridines 7 correlate with the inductive substituent parameters ρI in the Taft equation. This is to our knowledge the first direct determination of the resonance parameters ρRO.
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    Synthesis of Stereoisomeric Ufolanes (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1147-1157 
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    ISSN: 0009-2940
    Keywords: Acenaphthylene, dodecahydro- ; Acenaphthenes ; Ufolanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three of the six possible stereoisomers of dodecahydroacenaphthylene, t,t,t-ufolane (1), c,c,t-ufolane (3), and c,c,c-ufolane (5), have been synthesized for the first time. The configurations have been confirmed inter alia by an X-ray analysis of the precursors 11, 14, and 23 and the bromine adduct 24 of c,c,c-10-ufolene (19), the precursor of 5.
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    Synthese und Kristallstrukturen von Carbonyleisen- und Cyclopentadienyleisen-Zweikernkomplexen des 2,3-Diethyl-1,4-dihydro-1,4-dimethyl-1,4-diboranaphthalinsHerrn Professor Wolfgang Beck zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 987-991 
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    ISSN: 0009-2940
    Keywords: 1,4-Diboranaphthalenes ; Iron complexes ; Triple-decker complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Crystal Structures of Carbonyliron and Cyclopentadienyliron Dinuclear Complexes of 2,3-Diethyl-1,4-dihydro-1,4-dimethyl-1,4-diboranaphthalene*Reactions of the 1,4-Diboranaphthalene derivative 1a with (CO)3Fe(C8H14)2 lead to the orange anti dinuclear complex [(CO)3Fe(η6, η4-1a)Fe(CO)3] (4a) and to the cherry-red syn complex [(CO)3Fe(η4, η61a)Fe(CO)2] (5a). The X-ray structure of 5a reveals an Fe - Fe interaction (2.98 Å), 1a reacts with [(C5H5)Fe(C8H12)]2Zn to give the 30-VE triple-decker 7a, in which the diene of the benzo ring can be complexed with a Fe(CO)3 moiety to yield the trinuclear complex 9a.
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    URL: http://dx.doi.org/10.1002/cber.19921250502
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    Nickelkomplexe eines 1,4-Dihydro-1,4-Diboranaphthalin-DerivatesHerrn Professor Dr. Anton Meller zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 993-997 
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    ISSN: 0009-2940
    Keywords: 1,4-Diboranaphthalenes, 1,4-dihydro- ; Nickel complexes ; Double-decker ; Triple-decker ; Tetradecker, slipped ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nickel Complexes of a 1,4-Dihydro-1,4-diboranaphthalene Derivative*2,3-Diethyl-1,4-dihydro-1,4-dimethyl-1,4-diboranaphthalene (1) reacts with bis(1,5-cyclooctadiene)nickel to form the complexes 2 and 3. The latter is also obtained from 1 and bis(allyl)nickel. However, the reaction of 1 with Ni(C3H5)2 in a 1:1 ratio leads to 4 containing the 1,5-hexadiene ligand. The bis(allylnickel) triple-decker 5 is obtained from the dianion 12- and [(C3H5)NiBr]2. In addition, the diamagnetic 44-VE tetradecker 6 is formed in low yield. The constitutions of the complexes 2, 3, 4, and 6 are derived from spectroscopic data and are proven by X-ray structure analyses.
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    Epoxidation of Enamines by Dimethyldioxirane: Formation of 1,4-Dioxanes by Enamine Epoxide Dimerization (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1263-1266 
    Details
    ISSN: 0009-2940
    Keywords: Epoxidation ; Enamines ; Dimethyldioxirane ; 1,4-Dioxanes ; 1,3-Dipoles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1,4-dioxanes 3a-f, which constitute dimers of the enamine epoxides 2a-f, were obtained in excellent yields as crystalline products during the oxygen transfer to the corresponding enamines by dimethyldioxirane (DMD) in acetone. In methanol at -78°C, enamine 1b gave with dimethyldioxirane the β-hydroxy acetal 4b as the expected trapping product of the intermediary enamine epoxide 2b.
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    URL: http://dx.doi.org/10.1002/cber.19921250536
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    Siliciumverbindungen mit starken intramolekularen sterischen Wechselwirkungen, 47. Trisilacyclobutanimine (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1043-1046 
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    ISSN: 0009-2940
    Keywords: Trisilacyclobutanimines ; Cyclotrisilane, hexa-tert-butyl- ; Isocyanide insertion reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Silicon Compounds with Strong Intramolecular Steric Interactions, 47[1]. - TrisilacyclobutaniminesTreatment of hexa-tert-butylcyclotrisilane (4) with aryl isocyanides leads to the trisilacyclobutanimines 5-8. Reaction of the 1,4-diisocyanobenzene derivative 7 with two molecules of 4 leads to the double insertion product 9, the X-ray structure analysis of which shows the Si3CN framework atoms to be almost exactly coplanar. The planes of the two four-membered rings are strictly parallel whereas the linking phenylene group forms a 71.67° angle with these planes. The most striking features of these and of related compounds are their dark colours with longest wavelength absorptions between 500 and 540 nm.
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    Metallkomplexe mit funktionalisierten Schwefel-Liganden, III. Reaktionen von (Ph3P)2Pt(η2-C2H4) mit acyclischen und cyclischen Thiosulfinaten: Platin(II)-thiolato-Komplexe mit Sulfenato-Liganden. Kristallstrukturanalyse von (4-Sulfido-1-butansulfenato-S,S′)-bis(triphenylphosphan)platin(II) Herrn Professor Wolfgang Beck zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1047-1051 
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    ISSN: 0009-2940
    Keywords: Thiosulfinates ; Thiolato complexes ; Sulfenato complexes ; Platinum complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal Complexes of Functionalized Sulfur-Containing Ligands, III[1]. - Reactions of (Ph3P)2Pt(η2-C2H4) with Acyclic and Cyclic Thiosulfinates: Platinum(II)-thiolato Complexes with Sulfenato Ligands. Crystal Structure Determination of (4-Sulfido-1-butanesulfenato-S,S′)bis(triphenylphosphane)platinum(II) Oxidative addition of acyclic thiosulfinates R′-S(O)-S-R (1a: R′ = R = CH3; 1b: R′ = R = Ph; 1c: R′ = R = p-CH3C6H4;1d: R′ = p-ClC6H4, R = C6H5) to (Ph3P)2Pt(η2-C2H4) (4) leads to the monomeric trans-configurated complexes (Ph3P)2Pt[S(O)R′](SR) (5a-d) which loose one PPh3 ligand in solution and form the dimetallic thiolato-bridged compounds [(Ph3P)Pt[S(O)R′](μ-SR)]2. The cyclic thiosulfinates 1,2-dithiane S-oxide (2) and 1,4-dihydro-2,3-benzodithiine S-oxide (3) react with 4 to yield the monomeric seven-membered chelate (7) and the dimetallic complex [(Ph3P)Pt-S(O)-CH2-C6H4-CH2-μ-S]2 (8), respectively. In 7, characterized by X-ray diffraction, a tetrahedral distortion of the square planar coordination of the platinum(II) atoms is remarkable; the planes Pt,P(1),P(2) and Pt,S(1),S(2) form an angle of 16.1°.
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    Addition von Stannylenen an Iminoborane (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1079-1081 
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    ISSN: 0009-2940
    Keywords: Iminoboranes ; Stannylenes ; Aminostannation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition of Stannylenes to IminoboranesIminoboranes tBuB ≡ NR (R = tBu, Mes: 1 a, b) undergo aminostannation by the diaminostannylene Sn[N(SiMe3)2]2 (2b) to give (Me3Si)2N-B(tBu) = NR-Sn-N(SiMe3)2 (4a, b). The stannylene 4 b remains monomeric in the crystal (space group P21/n). The cyclic diaminostannylene [-Sn-N(tBu)-SiMe2-N(tBu)-] (3 b), instead, simply adds the boranes 1 a, b across one of its Sn-N bonds to form the bicyclo[2.2.0]hexene-type products 5a, b.
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    Synthese und Struktur von CpAlCl2-Verbindungen mit sterisch anspruchsvollen Substituenten (Cp = Me5C5, EtMe4C5) (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1107-1109 
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    ISSN: 0009-2940
    Keywords: Bulky substituents ; Aluminum compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Structure of CpAlCl2 Compounds with Sterically Demanding Substituents (Cp = Me5C5, EtMe4C5)[1]The compounds Cp*AlCl2 (3) (Cp* = Me5C5) and Cp′AlCl2 (4) (Cp′ = EtMe4C5) have been prepared by the reaction of Cp*SiMe3 (1) and Cp′SiMe3 (2) with AlCl3. The single-crystal X-ray structures of 3 and 4 are reported.
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    (Tetracyannaphthalocyaninato)eisen(II) mit Isocyaniden als axialen LigandenHerrn Professor Dr. Horst Prinzbach zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1243-1247 
    Details
    ISSN: 0009-2940
    Keywords: (Tetracyanonaphthalocyaninato)iron(II) ; Isocyanide complexes ; Semiconductors ; organic ; Iron complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (Tetracyanonaphthalocyaninato)iron(II) with Isocyanides as Axial Ligands(Tetracyanonaphthalocyaninato)iron(II) [(CN)4-2,3-NcFe; 6] is obtained by treating 2,3,6-tricyanonaphthalene (5) with iron(II) acetate. Compound 5 is synthesized according to the route given in Scheme 1. The mononuclear bisaxial isocyanide complexes (CN)4-2,3-NcFeL2 7-9 with L = tBuNC, cHxNC and AdNC as well as the bridged complex [(CN)4-2,3-NcFe(dib)]n (10) are formed as stable compounds by treating 6 with the neat ligands L. The spectroscopic properties of the complexes are described and compared with the analogous compounds (CN)4PcFeL2, 2,3-NcFeL2, 1,2-NcFeL2, and with PcFeL2. The bridged complex [(CN)4-2,3-NcFe(dib)]n (10) exhibits only poor semiconducting properties as compared to [2,3-NcFe(dib)]n. The oligomer 10 can be doped with iodine, and the resulting product [(CN)4-2,3-NcFe(dib)I1.4]n shows a powder conductivity s̰RT = 2 × 10-5 S/cm at room temperature.
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    URL: http://dx.doi.org/10.1002/cber.19921250534
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    Erste röntgenographische Charakterisierung N-lithiierter 4-Alkyliden-1,4-dihydropyridine des Typs [{4-(CH3CR)C5H4N}Li(TMEDA)]2: Vergleich von Kristall- und MNDO-Strukturdaten sowie Untersuchungen zur Lithium-Koordination in Lösung (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1267-1271 
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    ISSN: 0009-2940
    Keywords: 4-Alkylpyridines, lithiated ; Lithium coordination in solution ; Calculations, MNDO ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The First X-ray Structures of N-Lithiated 4-Alkylidene-1,4-dihydropyridines [{4-(CH3CR)C5H4N}Li(TMEDA)]2: Comparison of the X-ray and MNDO Geometries and Investigation of Lithium Coordination in SolutionThe 4-ethyl- and -isopropylpyridines 5a and b were transformed into the lithiated compounds [{4-(CH3CH)C5H4N}-Li(TMEDA)]2 (6a) and [{4-(CH3CCH3)C5H4N}Li(TMEDA)]2 (6b) by reaction with LDA and in the presence of TMEDA. These compounds were recrystallized from a toluene/hexane solution to obtain suitable crystals for X-ray investigations. Both structures are dimeric containing nonstoichiometric amounts of toluene in the crystals. The structural parameters of the heterocyclic moieties of 6a or b are typical of N-lithiated 4-alkylidene-1,4-dihydropyridines. MNDO geometries compare quite well with the X-ray structure of 6a. The lithium atom of 6a in solution prefers the same type of coordination as in the crystal: Two-dimensional 6Li,1H-HOESY showed Li contacts only to ortho-hydrogen atoms (Figure 3). 6a and b react differently with chlorotrimethylsilane (8). The variations of the alkylidene moieties of 6a and b, although seemingly small, are decisive: While the α,α-dimethyl compound 6b reacts exclusively as an N nucleophile, the α-methyl compound 6a functions also exclusively as a Cα nucleophile.
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    2-Oxabicyclo[3.2.1]oct-7-yl-Kationen (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1295-1296 
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    ISSN: 0009-2940
    Keywords: Wagner-Meerwein rearrangement ; Oxonium ions ; n Participation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Oxabicyclo[3.2.1]oct-7-yl Cations2-Oxabicyclo[3.2.1]octan-7-one (10) was prepared in five steps, starting from 3-cyclopenten-1-ol (5). The tosylhydrazone 11, derived from 10, was photolyzed in 0.5 N NaOD/D2O to give 〉99% of 2-oxabicyclo[3.2.1]octan-exo-7-ol (9) with equal distribution of D at C-1 and C-7. In contrast to the parent 6-bicyclo[3.2.1]octyl cation (1), the oxa analog 14 exhibits the same symmetry as was observed with the 6-oxa-2-norbornyl cation (13). The conformational effects that are evident in 1 are overruled by strong n participation.
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    Masthead (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992) 
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    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/cber.19921250601
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    The unusual oxidation of a 1,5,2,4-diazadiphosphorinan-6-one with tetrachloro-ortho-benzoquinone (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1325-1332 
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    ISSN: 0009-2940
    Keywords: 1,5,2,4-Diazadiphosphorinan-6-one ; Tetrachloro-ortho-benzoquinone ; Oxidation ; Spirophosphorane ; Spirophosphorate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidation of 2,4-bis(diethylamino)-1,5-dimethyl-1,5,2,4-diazadiphosphorinan-6-one (1b) with two equivalents of tetrachloro-ortho-benzoquinone (TOB) (2) leads to the cleavage of the original heterocycle and to the formation of a mixture of compounds, including the 1,3,2-diazaphosphetidine 6 (“λ6P-”) and the spirophosphorane 7. Compound 7 exists as two isomers that undergo slow spontaneous transformation in solution to compound 9, containing a six-coordinate phosphorus atom. When the oxidation of 1b is carried out in two stages, with the second equivalent of TOB being added after an interval of four days, the cleavage of the original molecule does not occur, and compound 17, containing a seven-membered ring with two phosphorus atoms of opposite formal charge and different coordination number (“λ4P+,λ6P-”) is formed. The structures of 6, 7, 9, and 17 were established by low-temperature X-ray analysis. Compound 6 displays crystallographic twofold symmetry; the coordination at phosphorus is octahedral, but distorted by the phosphetidine ring. The phosphorus atom in 7 possesses square pyramidal coordination geometry, the pyramid base being defined by the four oxygen atoms. Compound 9 (“λ6P-”) crystallized with two molecules of CDCl3. Compound 17 crystallized as a dichloromethane solvate. Distorted octahedral and tetrahedral geometries were observed for P1 and P2, respectively. The four-membered ring is planar. The bridging hydroquinone ligand displays much wider O-C-C(-O) and C-O-P angles than the chelating hydroquinone.
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    Substituierte 2,5-Dihydro-1,2,5-oxoniadiboratole, cis-1,2-Diborylalkene und 1,2,5-Oxadiborolane - Herstellung und Charakterisierung (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1351-1362 
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    ISSN: 0009-2940
    Keywords: 1,2,5-Oxoniadiboratoles, 2,5-dihydro-, organo-substituted ; 1,2,5-Oxadiborolanes, organo-substituted ; 1,3,2-Diboroxanes, substituted with unsaturated residues ; Boryl-germyl exchange ; cis-1,2-Diborylalkenes, organo-substituted ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted 2,5-Dihydro-1,2,5-oxoniadiboratoles, cis-1,2-Diborylalkenes, and 1,2,5-Oxadiborolanes - Preparation and CharacterizationThe potassium salts (A: R = R′ = Et; B: R2 = C8H14, R′ = Me; C: R2 = C8H14, R′ = Et) react with various electrophiles (H+, R+, Me3ElIV+) to form substituted 1,3,2-diboroxanes (1, iso8b) including 1,2,5-oxadiborolanes (2, 4, 6, 9, 10), dialkylvinylboranes (1'), 2,5-dihydro-1,2,5-oxoniadiboratoles (3, 5) and cis-1,2-diborylalkenes (7, 8). In particular, A-C react with HCl (as Me3NHCl/THF or HCl/Et2O) to give O[B(Et)C(Et) = CHR]2 (1a: R = Me; 1b: R = Et), R2BCR′ = CHEt (1'a: R = R′ = Et; 1'b: R2 = C8H14, R′ = Me; 1'c: R2 = C8H14, R′ = Et) and (2a: R,R′ = Et; 2b: R2 = C8H14, R′ = Me; 2c: R2 = C8H14, R′ = Et). With MeI in THF the cyclic compounds (3a) or (4b/4'b: R = Me; 4c/4'c: R = Et) and with Et3O · BF4 in CH2Cl2 the heterocycle - (5a) and cis-EtOB(C8H14)C(Et) = C(Et)BEt (5c) and/or (6b: R = Me; 6c: R = Et) are obtained. The reactions of A with ClElIVMe3 (ElIV = Si, Ge, Sn) lead to cis-Et2BC(Et) = CB(Et)OE1IVMe3 [ElIV=Si(7a), Ge (8a)] and to cyclic (9a). The salts B and C react with ClElIVMe3 (ElIV = Si, Ge) to form cis-C8H14BC(R) = C(Et)B(Et)OElIVMe3 (ElIV = Si: 7b: R = Me; 7c: R = Et; ElIV = Ge: 8b: R = Me, 8c: R = Et). On heating 8b isomerizes to cis-Me3GeC(Me) = C(Et)B(Et)OBC8H14 (iso8b). From B and C with ClSnMe3 the substituted 1,2,5-oxadiborolanes (10b/10'b: R = Me; 10c: R = Et) are obtained together with (C8H14B)2O.
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    Spektroskopischer Nachweis eines Bis(amino)silylens (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1375-1377 
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    ISSN: 0009-2940
    Keywords: Silicon(IV) diazide ; Photolysis ; Matrix isolation ; Silylene, bis(amino)- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Spectroscopic Identification of a Bis(amino)silyleneThe photolysis of the silicon diazide 3a in benzene solution and in an Ar matrix is described. Both irradiations cause the elimination of 3 equivalents of N2. Loss of N2 from 3a in benzene leads to the formation of the analytically investigated product or products 4 of uncertain structure. However, the matrix photolysis of 3a results in a compound which is stable up to 77 K and has been identified as the bis(amino)silylene 2d by comparison of its IR spectra with those of the homologous Sn and Ge compond.
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    Thermische Reorganisation und Cycloadditionen eines chiralen, nicht-racemischen Aziridinons (α-Lactams) sowie ab-initio-Berechnungen zur C2H3NO-Energie-Hyperfläche (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1249-1262 
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    ISSN: 0009-2940
    Keywords: Aziridinones, chiral, non-racemic ; α-Lactams ; Azetidin-2-ones, 4-imino- ; Oxazolidin-5-ones ; [2 + 1]Cycloreversion ; [3 + 1]Cycloaddition ; [3 + 2]Cycloaddition ; Zwitter-ions as intermediates ; Calculations, ab initio, RHF, UHF ; Iminooxiranes ; Oxaziridine, methylene ; Trimethylenemethanes, hetero- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal Reorganization and Cycloaddition Reactions of a Chiral, Non-Racemic Aziridinone (α-Lactam) and Ab Initio Calculations of the C2H3NO Energy Hypersurface[1]The thermal reorganization of the racemic (1 a) and the non-racemic aziridinone (R)-1 a (92% e.e.) is studied in solution in the temperature range of 100-140 °C. Besides traces of the imine 8, which is the product of a direct [2 + 1] cycloreversion of 1 a, the aldehyde 2 a and the isocyanide 4 a are formed in almost quantitative yield. A small fraction of the latter rear-ranges to the nitrile 3 or adds to unchanged 1 a to afford the iminoazetidinone (E)-5 a (5-10%), which is obtained when neat 1 a is heated in the presence of 4 a. The configuration of (E)-5 a is based on nuclear Overhauser experiments. The disappearance of 1 a follows a first-order rate law with k = 44 ° 10-6 s-1 at 130°C, while racemization of (R)-1 a is observed with k [(R)-1 a] = 8.1 · 10-6 s-1. The formal [3 + 1] cycloaddition of tert-butyl isocyanide (4 a) to (R)-1 a produces (E, R*)-5 a of unknown absolute configuration and a low enantiomeric excess (ca. 10%). The product (E, R*)-5 a is not racemized under the reaction conditions. The results are interpreted in terms of a nucleophilic attack of the isocyanide 4 a to C-3 of (R)-1 a resulting in an acyclic nitrilium type zwitterion (R)-21 which, to a large extend, racemizes via the ketene imine 22 before ring-closure to the final product (E,R)-5 a. - Dimethylformamide reacts with (R)-1 a at temperatures as low as 80-100 °C to give the diastereomeric oxazolidin-5-ones cis-and trans-15. The former is formed first and subsequently isomerizes to trans-15. The configuration of cis- and trans-15 is based on nuclear Overhauser experiments. The proton signals of the dimethylamino group of both cis- and trans-15 are temperature-dependent and split into two singlets of equal intensity at Tc = 271 and 250 K as a result of the retardation of two processes, viz. the N inversion and the rotation around the (C-NMe2) bond. In the reaction of (R)-1 a with dimethylformamide, the oxazolidinones (2R,5S)- and (2S,5S)-15 (85-90% e.e.) are formed which are hydrolyzed to the known α-hydroxyamide (S)-16. Hence, the configuration at C-5 of both cis- and trans-15 is (S), and the [3 + 2] cycloaddition of (R)-1 a to dimethylformamide involves inversion at C-3 of (R)-1 a. This result strongly suggests a nucleophilic attack of dimethylformamide to (R)-1 a rather than trapping of an acyclic aziridinone isomer. - In order to rationalize the observed reactions and reactivities, we performed high-level calculations on the parent aziridinone 29 and its cyclic (30, 31) and acyclic (32-35) isomers as well. Among the three-membered rings, 29 (MP2/6-31G*//6-31G*, Erel = 0.00 kJ mol-1) is lowest in energy, followed by the iminooxiranes (E)- and (Z)-31 (Erel = 30.8 and 26.0 kJ mol-1) and the methyleneoxaziridine 30 (Erel = 195.6 kJ mol-1). Energy-rich zwitter-ionic transition states (E)- and (Z)-32 (Erel = 281.9 and 234.6 kJ mol-1) are found with the RHF method. The UHF method is used for open-shell species. Thus, UHF/6-31G*//6-31G* optimizations result in the planar triplet states 33 having very low relative energies, but high spin contamination. UMP2/6-31G* single-point calculations of these triplets result in unrealistic, high relative energies. Complete UHF singlet geometry optimizations lead to the local minimum structure 35 of C1 symmetry (Erel = 34.9 kJ mol-1). At the highest computational level employed (UMP4SDTQ/6-31 + G*//6-31G*), a relative energy of 178.8 kJ mol-1 is obtained for 35. An activation energy of (170 ° 25) kJ mol-1 is estimated for the ring opening of the parent aziridinone 29 involving species with high diradical character.
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    Bis[bis(trimethylsilyl)methyl]galliumbromid und monomeres {Bis[bis(trimethylsilyl)methyl]gallium}[tris(trimethylsilyl)silyl]tellurid [(Me3Si)2CH]2Ga-TeSi(SiMe3)3 (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1547-1551 
    Details
    ISSN: 0009-2940
    Keywords: Gallium telluride, monomeric elementorganic ; Metathesis reaction between a digallium(4) and a ditellane derivative ; Gallium-tellurium π interaction, Tellurium compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis[bis(trimethylsilyl)methyl]gallium Bromide and Monomeric {Bis[bis(trimethylsilyl]methyl]gallium} [Tris(trimethylsilyl)silyl]telluride [(Me3Si)2CH]2Ga-TeSi(SiMe3)3Bis[bis(trimethylsilyl)methyl]gallium bromide GaBr[CH(SiMe3)2]2 (4), prepared from Ga2Br4 · 2 dioxane and bis(trimethylsilyl)-methyllithium in the molar ratio of 1:3, reacts with the sterically high-shielded lithium tris(trimethylsilyl)silyltelluride · DME to yield [(Me3Si)2CH]2Ga-TeSi(SiMe3)3 (5). 5 can also be synthesized by a metathetic reaction between tetrakis-[bis(trimethylsilyl)methyl]digallium(4) and bis[tris(trimethylsilyl)silyl]ditellane in toluene at 100°C. A crystal structure determination shows the compound to be monomeric in the solid state and the atoms of the central C2Ga-TeSi moiety to lie in the mirror plane of the molecule. The short Ga-Te distance of 253.5(1) pm as well as a hindered rotation (ΔErot ≍ 50 kJ · mol-1) as detected by NMR measurements might be interpreted in terms of a π interaction between gallium and tellurium.
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    Übergangsmetall-substituierte Diphosphene, XXVII[1] Synthese und Struktur des Diphosphirans (η5-C5Me5)(CO)2Fe-H[Cr(CO)5] (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1553-1557 
    Details
    ISSN: 0009-2940
    Keywords: Phosphido complexes ; Phosphaalkenes ; Diphosphiranes ; Chromium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition-Metal-Substituted Diphosphenes, XXVII[1]. - Synthesis and Structure of the Diphosphirane (η5-C5Me5)(CO)2Fe-PH[Cr(CO)5(η5-C5Me5)(CO)2FePH2 (5), prepared from (η5-C5Me5)(CO)2Fe-P(SiMe3)2 and ethanol, reacts with one equivalent of ClP = C(SiMe3)2 to give the diphosphirane (η5-C5Me5)(CO)2FePH (8). Compound 8 is converted into the iron chromium complex [(η5-C5Me5)(CO)2Fe-H]Cr(CO)5(9). In contrast, the reaction of 5 with two equivalents of ClP=C(SiMe3)2 results in the formation of the cyclotri-phosphane [(η5-C5Me5)(CO)2Fe-[CH(SiMe3)2] (12). The molecular structure of 9 is elucidated by single-crystal X-ray analysis.
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    Stabilisierung von Uran(IV)-Alkylen durch raumerfüllende Chelatliganden: Molekülstruktur von [PhC(NSiMe3)2]3UMe (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1313-1318 
    Details
    ISSN: 0009-2940
    Keywords: Actinides, organo- ; Uranium complexes ; σ-Alkyl complexes ; Chelating ligands ; Benzamidinate ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stabilization of Uranium(IV) Alkyls by Bulky Chelating Ligands: Molecular Structure of [PhC(NSiMe3)2]3UMeChelate ligand-stabilized uranium σ-methyl complexes are obtained in good yields by treatment of [RC6H4C-(NSiMe3)2]3UCl (1) with methyllithium. The molecular structure of [PhC(NSiMe3)2]3UMe (3a) has been determined by X-ray crystallography. A long uranium - carbon bond [249.8(5) pm] indicates steric crowding in the molecule. Analogously the dimethyluranium complex [(CF3)3C6H2C(NSiMe3)2]2UMe2 (4b) is prepared from [(CF3)3C6H2C(NSiMe3)2]2UCl2 and two equivalents of methyllithium. Reaction of 1 with NaBH4 yields the tetrahydroborates [RC6H4C(NSiMe3)2]3UBH4 (5). The strongly temperature-dependent 1H-NMR spectra of the complexes 1 and 3 have been studied in detail.
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    URL: http://dx.doi.org/10.1002/cber.19921250603
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    Elektronenüberschuß-Komplexe von Cobalt und Nickel mit Cyclobutadien-Liganden: Synthese, Cyclovoltammetrie und Reaktivität (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1589-1595 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron-Excess Complexes of Cobalt and Nickel with Cyclobutadiene Ligands: Syntheses, Cyclovoltammetry, and Reactivity[1]A cyclovoltammetric investigation of tetraphenylcyclobutadiene complexes [ML(C4Ph4)]+ [1: ML = NiCp; 2a: ML = Co(C6H6); 2b: ML = Co(mesitylene)] reveals a reversible reduction to paramagnetic complexes 1 and 2a,b with a 19-electron count, and a subsequent irreversible reduction to anions 1- and 2a,b- with a 20-electron shell. Preparative reduction by one equivalent of CpFe(HMB) (HMB = C6Me6) produces the novel 19-electron complexes 1 and 2b. Complex 1 can also be obtained by treatment of 1 · Br with one equivalent of CoCp2 at room temperature while reduction at -20°C with two equivalents of CoCp2 affords a novel C-C-linked adduct CpNi[μ,η3:η4-(C4Ph4-C5H5)]CoCp (5). Above -10°C a slow equilibrium between 5 and its components 1 and CoCp2 is observed with ΔH = 15 kJ/mol for the dissociation process. With an excess of the stronger reductant sodium amalgam the cations 1+ and 2a+ are reduced to give cyclobutenyl complexes ML(η3-1,2,3,endo-4-C4HPh4) [6: ML = NiCp; 7: ML = Co(C6H6)]. 1 reacts with p-nitrobenzyl bromide to give 1 Br and a p-nitrobenzyl addition product CpNi[η3-exo-4-(p-O2NC6H4CH2)-1,2,3,endo-4-C4Ph4] (11) while 2b reacts with MeI to give 2b · I and two isomeric methyl addition products (η5-1,3,5,exo-6-C6H3Me4)Co(C4Ph4)] (12) and (mes)Co(η3-exo-4-Me-1,2,3,endo-4-C4Ph4) (13). Sodium-amalgam reduction of the tetramethylcyclobutadiene cations [(arene)Co(C4Me4)]+ (4a: arene = C6H6; 4b: arene = mesitylene) affords diamagnetic dinuclear compounds of type 8-10 with C-C linkages between C4Me4/C4Me4, arene/C4Me4, and arene/arene rings, respectively.
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    URL: http://dx.doi.org/10.1002/cber.19921250713
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    Enol cation radicals in solution, 3[1] Reaction of enol cation radicals in the presence of nucleophiles (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1611-1620 
    Details
    ISSN: 0009-2940
    Keywords: Radicals ; enol cation ; Benzofurans ; Oxazoles ; Voltammetry, cyclic ; Carbocations ; α-carbonyl ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The one-electron oxidation chemistry of three diaryl-substituted enols, 1,1-dimesityl-1-propen-2-ol (7), 1,2-dimesityl-1-propen-1-ol (8), and 2-mesityl-2-phenylethenol (9), has been examined. As a consequence of the pronounced steric shielding around the β-carbon, 7 does not react with nucleophiles upon addition of 2 eq. of oxidant, but cyclizes to yield benzofuran 18. Under identical conditions, the less shielded enols 8 and 9 react with methanol and other nucleophiles. Several mechanistic hypotheses for nucleophile incorporation are tested, thus allowing the second part of the α-umpolung reaction of ketones via enol cation radicals to be elucidated mechanistically. Fast-scan cyclic voltammetry studies (2000 V · s-1) show no reversible wave of the enol cation radicals. The corresponding methyl enol ether cation radicals, however, have a lifetime of several seconds at -10°C, and the kinetics of their reactions with acetonitrile and methanol was probed. The results obtained are consistent with fast deprotonation being the primary reaction of enol cation radicals. Under the given oxidative conditions the radicals formed are further oxidized. Consequently one-electron oxidation of enols provides an interesting entry to α-carbonyl carbocation chemistry.
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    URL: http://dx.doi.org/10.1002/cber.19921250716
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    Organische Synthesen mit Übergangsmetall-Komplexen, 59[1] Cyclobutanimine aus Carbenchrom- oder -wolfram-Komplexen, Isocyaniden und Alkenen durch [2 + 2]-Cycloadditionen intermediärer Ketenimin-Komplexe; Liganden-Abspaltung mit Pyridin (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1627-1633 
    Details
    ISSN: 0009-2940
    Keywords: Cyclobutanimines via carbene complexes ; 10-Iminotricyclo[5.3.0.02,9]deca-3,5-dienes ; (Cycloheptatrien-1-ylmethyl)carbene complexes of chromium and tungsten ; Ketenimine complexes, [2 + 2] cycloadditions with alkenes ; Ketene complexes, [2 + 2] cycloadditions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organic Syntheses via Transition Metal Complexes, 59[1]. - Cyclobutanimines from Carbenechromium or -tungsten Complexes, Isocyanides, and Alkenes by [2 + 2]-Cycloaddition Reactions of Ketenimine Complexes; Ligand Disengagement with Pyridine10-Iminotricyclo[5.3.0.02,9]deca-3,5-diene complexes syn/anti-4 are obtained in yields higher than 90% by the addition of isocyanides RNC 2 [R = c-C6H11 (a), CH3 (b)] to (cycloheptatrien-1-ylmethyl)carbene complexes LnM=C(OEt)CH2(C7H7) 1 [LnM = Cr(CO)5 (a), W(CO)5 (b)]. The reactions involve an intermediate formation of ketenimine complexes LnM[RN=C=C(OEt)CH2C7H7] 3 by the insertion of 2 into the M=C bonds of 1. Complexes 3 isomerize to give the cyclo-butanimines 4 by an intramolecular [2s + 2a]-cycloaddition reaction of the ketenimine to the alkene unit. The structure of anti-4c has been determined by a crystal structure analysis. Complexes 4 react with pyridine by the fragmentation of the four-membered ring to yield a tetrahydroazulen-1-imine 6 which was hydrolyzed to the corresponding ketone 7;7 is also obtained along an independent route by the photolysis of 1a in the presence of carbon monoxide. The first isolated product of the latter reaction is the tricyclo[5.3.0.02,9]deca-3,5-dienone 9, which presumably is formed via an intermediate ketene complex N and the tricyclic ketone O; 9 on warming with pyridine rearranges to 7.
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    trans-1-(Dimethylamino)-1,3-butadiene - Concerted and Stepwise (4 + 2) Cycloadditions (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1647-1656 
    Details
    ISSN: 0009-2940
    Keywords: Cycloadditions ; Diels-Alder reactions ; Kinetics ; Zwitterionic intermediates ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: trans-1-(Dimethylamino)-1,3-butadiene is allowed to react with methyl acrylate, acrylonitrile, maleo- and fumaronitrile, dimethyl maleate and fumarate, as well as with dimethyl dicyanomaleate and dicyanofumarate. In all cases except the two last ones where only a single isomer is obtained mixtures (endo/exo) of cycloadducts are formed. Structures are determined by a combination of one- and two-dimensional NMR spectroscopy. The E/Z isomeric maleo- and fumaronitrile add stereospecifically to the diene. Cycloaddition of dimethyl maleate and fumarate leads to the same mixture of isomers in almost the same ratio. The reaction of dimethyl dicyanomaleate and dimethyl dicyanofumarate yields a cycloadduct which seems to be the thermodynamically most stable one. The results are interpreted in such a manner that a concerted cycloaddition takes place with maleo- and fumaronitrile, while stepwise reactions, presumably proceeding via zwitterions, are observed with dimethyl maleate, fumarate, the strongly electrophilic dimethyl dicyanomaleate and dicyanofumarate. With increasing capability of the dienophile to stabilize a negative charge the mechanism changes from a concerted to a stepwise reaction.
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    Konkave Farbstoffe mit Azobenzol-Einheiten als Chromophore, Photoschaltelemente und hohlraumbildende Bausteine (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1675-1686 
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    ISSN: 0009-2940
    Keywords: Azobenzene ; Concave dyes ; Dyes ; Isomerism, in-out ; Macrocycles ; Molecular switches ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Concave Dyes with Azobenzene Units as Chromophores, Photoswitchable and Cavity-Forming ElementsFive monomacrocyclic (12a-e) and three types of threefold azobenzene-bridged oligomacrocyclic compounds (15, 17, 28, 31) have been synthesized. Due to the cavity-forming chromophores at the periphery of these molecules they represent concave dyes. The watersoluble monocycles 12b-e were photoisomerized and investigated before and after E/Z isomerization with regard to their host properties for small neutral organic guest compounds. The bicyclic azobenzene derivative 31 with triphenylethane spacers exhibits in/out isomerism. The in/out isomer 31c was separated by HPLC from 31a and b, which are in equilibrium at room temperature. The tris(2-aminoethyl)amine-capped Schiff bases 15 and 17 form complexes with Cu(CH3CN)4BF4.
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    Ein Zirconiumamid-Komplex mit Si-β-H-Zr-Wechselwirkungen (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1405-1407 
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    ISSN: 0009-2940
    Keywords: Amido ligands ; Zirconium complexes ; β-Hydrogen effect ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Zirconium Amide Complex with Si-β-H-Zr InteractionsZrCl4 (1) reacts in diethyl ether with Li[N(SiHMe2)2] (2) to form the title compound of formula [ZrCl(μ-Cl){N(SiHMe2)2}2]2 (3). A single-crystal X-ray structure analysis in combination with IR data provides evidence for an unprecedented type of β-hydrogen interactions between a silicon-attached hydrogen atom of the bis(dimethylsilyl)amide ligand and the zirconium atom (Zr-N-Si-H).
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    URL: http://dx.doi.org/10.1002/cber.19921250617
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    Wasserstoffübertragungen, 20[1a] Konkurrierende pericyclische Reaktionen von Dihydroarenen mit gespannten Cycloalkenen und -alkinen (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1431-1437 
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    ISSN: 0009-2940
    Keywords: Cycloadditions ; Hydrogen transfer ; Ring strain ; Calculations, AM1 ; Transition states ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogen Transfer Reactions, 20[1a]. - Competitive Pericyclic Reactions of Dihydro Arenes with Strained Cycloalkenes and CycloalkynesWhile several highly strained cycloalkenes and cycloalkynes react with dihydroarenes to give products of Diels-Alder or ene reactions only, 7 dehydrogenates two dihydroarenes as well. Semiempirical AM1 calculations on the transition structures for the [4 + 2] cycloadditions and the hydrogen transfer reactions show the independence of their geometry from the starting compounds. The preference for dehydrogenations by 7 is caused by both steric and solvent effects.
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    Benzoanellated centropolyquinanes, 11. Synthesis of tribenzotriquinacene and some centro-substituted derivativesDedicated to Professor Hans-Friedrich Grützmacher on the occasion of his 60th birthday. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1449-1460 
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    ISSN: 0009-2940
    Keywords: Polycyclic compounds ; Centropolyindans ; Triquinacenes ; Cyclodehydration ; 1,3-indandiones ; 1,3-Indandiols ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of tribenzotriquinacene (1a) and five centro-substituted derivatives, 1b-1e and 1g, as well as of the related diindan 13 are reported. The three-step synthetic sequences include the reduction of suitably substituted 2-benz-hydryl-1,3-indandiones 3 to the corresponding 1,3-indandiols 4 and the twofold cyclodehydration of the latter to close two additional five-membered rings at a time. Although the yields of the cyclodehydration step 4 · 1 are only low to moderate (10-33%), the overall approach allows the preparation of 5-50-gram amounts of the centropolyindans in most cases by starting from simple 1,3-indandiones 2a-2c. This includes the new synthesis of the parent tribenzotriquinacene (1a). The related Cs-symmetrical diindan, 4b,9,9a,10-tetrahydroindeno[1,2-a]indene (13), has been prepared in high yield by using the same cyclodehydration technique. Scope and limitations of the double cyclodehydration strategy are described concerning the synthesis of 1,3-indandiones with bulky substituents at C-2 and the cyclization of 1,3-indandiols with an aptitude to undergo heterolytic cleavage of an exocyclic C-2-C-α bond, in particular 4f. The course of the reduction of the 2,2-disubstituted 1,3-indandiones with lithium aluminum hydride is discussed on the basis of the stereochemistry of the product 1,3-indandiols.
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    URL: http://dx.doi.org/10.1002/cber.19921250623
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    Regioselective preparation of iodinated phloroglucinols (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1501-1506 
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    ISSN: 0009-2940
    Keywords: Resorcinols, methoxy-, monoprotected ; Iodination, mild ; Iodobenzenes, electron-rich ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A range of mono- and diiodinated phloroglucinols with differential protection of two hydroxy groups has been prepared.
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    URL: http://dx.doi.org/10.1002/cber.19921250628
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    Alkylierung von Chinonen mit O-silylierten Ketenacetalen in LiClO4/Ether als ReaktionsmediumHerrn Professor Günther Maier zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1513-1515 
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    ISSN: 0009-2940
    Keywords: Quinones ; Ketene acetals, O-silylated ; Mukaiyama reaction ; 2(3H)-Benzofuranone ; Homogentisic acid ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkylation of Quinones by O-Silylated Ketene Acetals in LiClO4/Ether as Reaction MediumO-Silylated ketene acetals (2, 5) undergo 1,4-conjugative addition to α,β-unsaturated carbonyl systems of quinones 1 in the presence of lithium perchlorate in ether to form 2(3H)-benzofuranones 3
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    Synthesis and molecular structure of tin(IV) 1-pyrrolecarbodithioates (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1523-1528 
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    ISSN: 0009-2940
    Keywords: 1-Pyrrolecarbodithioate derivatives ; Tin complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1-pyrrolecarbodithioate complexes of tin, PhSnCl(S2CNC4H4)2 (1) and Sn(S2CNC4H4)4 (2) have been synthesized and characterized by IR and NMR spectra (1H, 13C and 119Sn). δ119Sn suggests hexacoordination for 1 and an even higher coordination number for 2. X-ray structure determinations of these as well as of Me2Sn(S2CNC4H4)2 (3) have shown that 3 is one of the few known examples with a skew-trapezoidal bipyramidal configuration. 1 attains approximately a cis-octahedral geometry with two bidentate carbodithioate ligands with the Cl atom and the phenyl group in cis position. Complex 2 possesses two bidentate ligands while the other two are essentially anisobidentate leading to a structure between an octahedraon and a dodecahedron.
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    Derivate des Borols, XVIII. Tricarbonyl[η5-(1-phenylborol)]eisen: Zur Reaktivität der koordinierten Liganden (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1801-1805 
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    ISSN: 0009-2940
    Keywords: (Borole)carbonyliron derivatives, electrophilic substitution, nucleophilic addition, reduction ; Iron complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Derivatives of Borole, XVIII. - Tricarbonyl[η5-(1-phenylborole)]iron: Reactivity of the Coordinated LigandsThe borole complex (C4H4BPh)Fe(CO)3 (1) undergoes Friedel-Crafts acetylation (MeCOCl/AlCl3) at the meta-position of the phenyl substituent while the derivatives (C4H4BPh)Fe(CO)2L (3, a: L = NMe3′ b: L = PMe3) are acetylated at the 2-position of the borole ring. Organolithium reagents (LiMe, LiBu) add to 1 at the boron atom below - 50°C while nucleophilic attack at the carbonyl C atom takes place at higher temperature with formation of acyl anions [(C4H4BPh)Fe(CO)2(COR)]- (6a,b-). The Fischer carbene complex (C4H4BPh)Fe(CO)2[C(OMe)Me] (7) is obtained from 6a-/[Me3O]BF4. Complex 1 reacts with LiN(SiMe3)2 to give [(C4H4BPh)Fe(CO)2(CN)]- (8-) and with 5 M NaOH/C6H6/NBu4HSO4 to produce the hydride NBu4-[(C4H4BPh)FeH(CO)2] (NBu4 · 9). A highly reactive dianion [(C4H4BPh)Fe(CO)2]2- (102-) is obtained by deprotonation of 9- or by reduction of 1 or 3a in THF at -70°C. Treatment of 102- with Ph3SnCl gives [(C4H4BPh)Fe(CO)2(SnPh3)]- (11-) which is isolated as NEt4 · 11. Slow reduction of 3a with sodium amalgam in THF at -30°C produces doubly CO-bridged cis-[{(C4H4BPh)Fe(CO)2}2]2- (122-) which is protonated to the μ2-hydrido anion [μ-H-{(C4H4BPh)Fe(CO)2}2]- (13-).
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    Conformation in the Solid State and in Solution of 3,3′(4H,4′H)-Spirobi[2H-1,5-benzodioxepin] (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1837-1841 
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    ISSN: 0009-2940
    Keywords: Circular dichroism ; Spiranes, absolute configuration and conformation of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The “spiro-coplanar” conformation of 6,6′-methoxycarbonyl-3,3′(4H,4′H)-spirobi[2H-1,5-benzodioxepin] (1b) and the 3P configuration of the corresponding menthol ester 1c have been determined from chiroptical data by application of the exciton theory. The solid-state conformation of the central part of the menthol ester molecule is “spiro-coplanar”, too, with nearly D2 symmetry. The menthol moieties have chair conformations, and the absolute configurations at their chiral centers have been assigned using enantiomer-sensitive Bijvoet pairs; they are in agreement with the known absolute configuration of menthol.
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    Zink-Komplexe von Tris(2-pyridyl)phosphan und Tris(2-pyridyl)arsan (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1575-1581 
    Details
    ISSN: 0009-2940
    Keywords: Zinc complexes ; Tridentate ligands ; Pyridine donors ; Phosphanes ; Arsanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Zinc Complexes of Tris(2-pyridyl)phosphane and Tris(2-pyridyl)arsaneReactions of zinc salts with the two title ligands are described which reveal several dissimilarities in their coordination behavior. From tris(2-pyridyl)phosphane (1) and the zinc halides compounds with an L2Zn3 stoichiometry are isolated which, according to their Raman spectra, have the constitution [LZnHal]2[ZnHal4]. With tris(2-pyridyl)arsane (2) the zinc halides form the 1:1 complexes LZnHal2. With Zn(SCN)2 and 1 only the L2Zn2+ species can be observed, while 2 produces the molecular complex LZn(SCN)2. Both 1 and 2 form a neutral 1:1 compound with Zn(NO3)2 which was shown for 1 · Zn(NO3)2 by an X-ray structure analysis to consist in the solid state of octahedral complexes containing tridentate 1 and both monodentate and bidentate NO3-. According to NMR spectroscopy this constitution seems to be maintained in solution. While the complexes 1 · ZnHal2 are insoluble, the complexes 2 · ZnHal2 and 2 · Zn(NO3)2 can be shown by NMR to undergo an equilibration in solution involving the LZn2+ and L2Zn2+ species of which only the LZn2+ species crystallizes as LZnX2. The zinc salts Zn(ClO4)2 and Zn(BF4)2 with noncoordinating anions react with 1 and 2 to form exclusively the L2Zn2+ complexes whose highly symmetrical octahedral geometry was ascertained for (1)2Zn(ClO4)2 by an X-ray structure analysis.
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    Organotin cations stabilized by π coordination - synthesis and NMR studies in solution and in the solid state (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1597-1603 
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    ISSN: 0009-2940
    Keywords: Organoboration ; Tin compounds ; NMR, multinuclear ; NMR, 119Sn ; NMR, solid-state ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The organoboration of tetraalkynyltin compounds [Sn-(C≡CR1)4 (1): R1 = Me (a), Et (b), Pr (c), iPr (d), tBu (e)] with triethylborane (2) proceeds stepwise. Intermediates with a cationic triorganotin (3, 5) and a dicationic diorganotin fragment (4), stabilized by intramolecular coordination of one and two alkynyl moieties, respectively, were isolated (3e, 4a) and/or identified by multinuclear NMR in solution (1H, 11B, 13C, 119Sn) and in the solid state (13C and 119Sn CP/MAS) (3e, 4a). The magnitude of 1J(13C≡13C) in 4a (101.0 Hz) is significantly smaller than that for sodium triethyl-1-propynylborate (7) (119.2 Hz), proving the weak coordination of the C≡C bond to the dicationic tin fragment. The final products of the organoboration, 1,4,6,9-tetraalkyl-2,7-bis(diethylboryl)-3,8-diethyl-5-stannaspiro[4.4]nona-1,3,6,8-tetraenes (6b-6e) were obtained in high yield.
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    Folgereaktionen von Sulfenen aus Sulfonylchloriden und tertiären Aminen, 3[1,2] Kristallstrukturanalyse von Bis(trimethylammoniosulfonyl)methanid-tetraphenylborat. - n-σ*-Wechselwirkungen (Hyperkonjugation und Homohyperkonjugation) in Sulfen-Amin-S,N-Addukten (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1621-1626 
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    ISSN: 0009-2940
    Keywords: Bis(trimethylammoniosulfonyl)methanide tetraphenylborate ; Sulfene-amine adducts ; Hyperconjugation, negative ; Homohyperconjugation, negative ; n-σ* interactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Secondary Reactions of Sulfenes from Sulfonyl Chlorides and Tertiary Amines, 3[1,2]. - Crystal Structure Analysis of Bis(trimethylammoniosulfonyl)methanide Tetraphenylborate. - n-σ*-Interactions (Hyperconjugation and Homohyperconjugation) in Sulfene - Amine S,N-AdductsBis(trimethylammoniosulfonyl)methanide chloride (3b) could be obtained in 97% yield by reaction of methanedisulfonyl dichloride (5) with three equivalents of trimethylamine. X-ray analysis of the tetraphenylborate 3c reveals that the conformation of the cation is determined by nC-σ*S-N interactions (negative hyperconjugation) and by nC-σ*N-C interactions (negative homohyperconjugation). These effects were deduced from alterations of the bond lengths within the S-N-C chains which are coplanar to the occupied pz orbital at the central C atom. Comparison with known crystal structure data shows, that sulfene - amine S,N-adducts generally have the zwitterionic ammoniosulfonylmethanide structure 3, stabilized by nC-σ* interactions.
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    A Stopped-Flow Kinetic Study of the Reaction of trans-1-(Dimethylamino)-1,3-butadiene with Dimethyl Dicyanofumarate (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1665-1667 
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    ISSN: 0009-2940
    Keywords: Zwitterion formation and decay, kinetics of ; Cycloadditions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: trans-1-(Dimethylamino)-1,3-butadiene and dimethyl dicyanofumarate react in acetonitrile and dichloromethane at -40°C with a second-order rate constant of 107 to 108 l mol-1 s-1. This was determined by following the decay of the UV absorption of diene and dienophile with a stopped-flow spectrofluorimeter. After disapperance of the reagents a new absorption (λmax = 400 nm, lgε = 2.514) is recorded which decays by a first-order process. The analysis of the kinetic data (Ea = 14.5 ± 0.1 kcal mol-1, lgA = 14.71 ± 0.05, ΔH# = 14.1 ± 0.1 kcal mol-1, δS# = 7.2 ± 0.2 cal mol-1 K-1, ΔG# = 11.95 ± 0.01 kcal mol-1) in combination with stereochemical studies on the cycloaddition of the E/Z isomeric dienophiles dimethyl dicyanofumarate and dicyanomaleate leads to the interpretation that the new species is a zwitterion.
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    Mehrfach verbrückte Triphenylmethane (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1687-1695 
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    ISSN: 0009-2940
    Keywords: Host-Guest chemistry ; Inclusion compounds ; Macropolycyclic compounds ; Heterocyclic compounds ; Supramolecular chemistry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multiple-Bridged TriphenylmethanesUp to fourfold-bridged macrocyclic compounds bearing triphenylmethane units which form a large molecular cavity were prepared for the first time. The macrobicyclus 4 crystallizes from acetonitrile as 1:1 adduct and from phenylacetonitrile as 1:3 adduct with the respective solvent. The X-ray structures of these complexes are compared with the related 1:5 adduct of 13 with benzene.
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    Struktur von α-(Dimethylamino)benzyllithium in Lösung: Dynamisches Gleichgewicht zwischen einer η1- und einer η3-SpeziesHerrn Professor Günther Maier zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1753-1762 
    Details
    ISSN: 0009-2940
    Keywords: Benzyllithium, α-(dimethylamino)- ; NMR, 6Li ; HOESY, 6Li-1H ; Calculations, MNDO ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure of α-(Dimethylamino)benzyllithium in Solution: Dynamic Equilibrium between an η1 and an η3 SpeciesTemperature-dependent 1H- and 13C-NMR-spektroscopic shifts observed in tetrahydrofuran are indicative of an equilibrium between a high-temperature η3 and a low-temperature η1 species. MNDO calculations are in accord with this view, and HOESY experiments proof it, too. The equilibrium is controled by solvation or complexation, low Lewis basicity of the solvent or bidentate ligands favoring the η3, high Lewis basicity or tridentate ligands the η1 species. Equilibrium as well as rate constants have been estimated, and from their temperature dependence the thermodynamics of the equilibrium and the activation barriers were calculated.
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    Photoelectron Spectrum and Electronic Structure of Indigo (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1773-1775 
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    ISSN: 0009-2940
    Keywords: Photoelectron spectrum ; Electronic structure ; Indigo ; Calculations, AM1, HAM/3, MNDO, PM3 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The He(I) photoelectron spectrum of indigo has been obtained by evaporating the compound at ca. 400°C. The ionization potentials are related to orbital energies or electronic states of the radical cation with the aid of semi-empirical SCF-MO calculations. A satisfactory interpretation of the spectrum up to 18 eV is obtained according to the HAM/3 method.
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    URL: http://dx.doi.org/10.1002/cber.19921250733
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    Metallcarbonyl-Synthesen, XXI. Einfache Synthese eines präparativ nützlichen Alkoxy(carbonyl)metallats (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1795-1799 
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    ISSN: 0009-2940
    Keywords: Carbonyl complexes ; Rhenium complexes ; Alkoxy carbene, structure of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal Carbonyl Syntheses, XXI. - Straightforward Synthesis of a Synthetically Useful Alkoxy(carbonyl)metallateAnionic methoxy complexes are formed upon carbonylation of ammonium perrhenate in methanol at 230-240°C. Thus, the dinuclear ionic complex [N(CH3)4][Re2(CO)6(μ-OCH3)3] (2) results in 80% yield at CO pressures of ca. 100 bar, while the trinuclear derivative [N(CH3)4][Re3(CO)9(μ3-OCH3)3(μ3-OCH3)] (3) is due to lower pressure conditions (ca. 50 bar); 2 yields the bis(carbene) complex 4 of formula fac-Re(CO)3L2I upon treatment with a bis(imidazolium) iodide, thus demonstrating that carbonylrhenium chemistry not necessarily depends on the availability of Re2(CO)10.
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    Regiospezifische Insertion von Phenylacetylen in die Zr—P-Bindung von Cp2Zr{P(SiMe3)2}(Cl) und Folgereaktionen des Insertionsprodukts (Z)-Cp2Zr{C(Ph) = C(H)P(SiMe3)2}(Cl) (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1815-1819 
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    ISSN: 0009-2940
    Keywords: Alkyne insertion ; Ethenyl ligands, 2-(silylphosphanyl)- ; Zirconocenes ; Zirconium complexes ; Phosphido ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Regiospecific Insertion of Phenylacetylene into the Zr—P bond of Cp2Zr{P(SiMe3)2}(Cl) and Derivatives of the Insertion Product (Z)-Cp2Zr{C(Ph) = C(H)P(SiMe3)2}(Cl)The reaction of Cp2Zr{P(SiMe3)2}(Cl) (1) with phenylacetylene in boiling toluene yields regiospecifically the insertion product (Z)-Cp2Zr{C(Ph) = C(H)P(SiMe3)2}(Cl) (2) which reacts with MeLi or nBuLi by forming the corresponding alkyl-substituted zirconocene derivatives (Z)-Cp2Zr{C(Ph) = C(H)P(SiMe3)2}(R) [R = Me (3), nBu (4)]. The attempt to prepare the C(Ph) = C(H)P(SiMe3)2- ligand directly from Li(THF)2P(SiMe3)2 and phenylacetylene yields HP(SiMe3)2 and LiC≡CPh. An X-ray structure determination of 2 and 3 was carried out.
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    Übergangsmetall-substituierte Diphosphene, XXVIII. Synthese und Strukturbestimmung der ersten 1,2-Diaza-3,4-diphosphetidine und (2E,8E)-1,7-Dioxa-3,4,9,10-tetraaza-5,6,11,12-tetraphospha-2,8-cyclododecadiene (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1821-1827 
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    ISSN: 0009-2940
    Keywords: Diphosphenyl ligands ; Δ1-1,2,4-Triazoline-3,5-diones ; 1,2-Diaza-3,4-diphosphetidines ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition-Metal-Substituted Diphosphenes, XXVIII. - Synthesis and Structures of the First 1,2-Diaza-3,4-diphosphetidines and (2E,8E)-1,7-Dioxa-3,4,9,10-tetraaza-5,6,11,12-tetraphospha-2,8-cyclododecadienes(η5-C5Me5)(CO)2Fe—P = P—Mes*(Mes* = 2,4,6-tBu3C6H2) reacts with one equivalent of the Δ1-1,2,4-triazoline-3,5-diones (2a: R = Ph; 2b: R = 4-EtOC6H4) in benzene to give the first 1,2-diaza-3,4-diphosphetidines 3a, b. When the same reaction is performed in diethylether the novel (2E,8E)-1,7-dioxa-3,4,9,10-tetraaza-5,6,11,12-tetraphospha-2,8-cyclododecadienes 4a, b are isolated as the sole products. The molecular structures of 3a and 4b are established by single-crystal X-ray analysis.
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    Langgestreckte Moleküle von Dispiro[5.1.5.2]-Typ (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1865-1871 
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    ISSN: 0009-2940
    Keywords: Spiro compounds ; Liquid crystals ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rod-Like Dispiro[5.1.5.2] CompoundsA number of symmetrically and unsymmetrically substituted spiro compounds were synthesized starting from the dispiro[5.1.5.2]trione 1. The trans-trans isomers of 2, 3, 6-10, and 11 were separated from the cis-cis and cis-trans isomers. From the trispiro compound 4 derivatives bearing differing substituents were synthesized. The tetraspiro compounds 5 were obtained in one step. Some of the compounds functionalized with flexible sidegroups show narrow liquid-crystal phases.
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    Von vierfach funktionalisierten Cyclophanen zu rohrförmigen Molekülen (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1881-1887 
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    ISSN: 0009-2940
    Keywords: Heteraphanes ; Cyclophanes ; Macrocycles ; Tube-shaped molecules ; Phanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: From Fourfold Functionalized Cyclophanes to Tube-Shaped MoleculesA series of fourfold functionalized 2,11-dithia- and 2,11-diaza[3.3]cyclophanes 15-17 and 18-22, resp., is prepared by using a new multistep-strategy starting from 7 or m-xylene, respectively. The cyclophanes are used to construct tube-shaped molecules of type 24 by macrocyclization reactions of e. g. 21 and 22. Macrocycle 24 turns out to be conformationally flexible.
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    Synthese und optische Eigenschaften endständig substituierter konjugierter Polyene mit Bicyclo[2.2.2]octan als Spacer (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2103-2110 
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    ISSN: 0009-2940
    Keywords: Polyenes, conjugated ; Bicyclo[2.2.2]octane as spacer ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Optical Properties of Terminally Substituted Conjugated Polyenes with Bicyclo[2.2.2]octane as SpacerThe conjugated polyenes 10, 11, and 17 respectively, with 9-anthryl- and 2-tetraphenylporphyrinyl (TPP) terminal groups and a bicyclooctane unit incorporated into the polyene chain were synthesized by Wittig olefinations. In all cases it was possible to obtain the all-(E) compounds from the (E)/(Z)-isomeric mixtures by chromatographic purification and several recrystallizations. From the UV/Vis spectra the separation of the TPP group and the polyene chain in 10, 11, and 17 can be deduced whereas in 10 and 11 the two conjugated double bonds are amalgamated into the anthryl group. In 17 the anthryl group is electronically separated from the polyene chain, and a selective excitation therefore is possible.
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    Photoreactions of Enones with Amines - Cyclization of Unsaturated Enones and Reductive Ring Opening by Photoinduced Electron Transfer (PET)Dedicated to Professor Dr. Hermann Stetter (Aachen) on the occasion of his 75th birthday. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2119-2127 
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    ISSN: 0009-2940
    Keywords: Photoinduced electron transfer ; Cyclization ; Ring opening ; Enones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photolysis of the unsaturated enones 1 yields [2 + 2] cycloaddition products 2 and 3 with varying regioselectivity. Under electron-transfer conditions (PET) spirocyclic products 4 are formed. The straight [2 + 2] cycloaddition products 2b,c,f are converted to the spirocyclic products 4b,c,f under the same reaction conditions. The cyclobutane 5 and the cyclopropane 11 also undergo this new reductive ring opening reaction, while the stabilized system 7 is converted to reduced ringenlarged triquinane 10 which may be interesting in natural product synthesis. - Irradiation of 2-cyclohexen-1-one (14) in the presence of N,N-dimethylallylamine (15) leads to the decahydroisoquinoline 18. A mechanism involving radical intermediates is discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250921
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    Reaktionen von Komplexliganden, LI. Synthese und Reaktionen stabiler (Carben)tetracarbonyl-Chelatkomplexe des Molybdäns (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2143-2148 
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    ISSN: 0009-2940
    Keywords: Molybdenum complexes ; Chelate complexes ; Carbene ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of Complex Ligands, LI[1]. - Synthesis and Reactions of Stable (Carbene)tetracarbonyl Chelate Complexes of MolybdenumThe stable (carbene-C,O, -C,N, and -C,S)tetracarbonyl chelate complexes of molybdenum 2b-2c have been obtained by mild decarbonylation of their corresponding pentacarbonyl precursors 1b-1c. The chelate complexes have been characterized by elemental analyses and spectroscopic data. In addition, the structure of C,N chelate 2c has been confirmed by X-ray analysis. In contrast to its C,N and C,S analogues, the C,O chelate complex 2a undergoes ring opening at temperatures as low as -40°C upon addition of triphenylphosphane. At 20°C the phosphane-substituted chelate complex 4a is obtained. C,N and C,S chelate complexes require higher temperatures for the reaction to give similar fac-tricarbonyl complexes 4b-4c.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250924
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  • 97
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    Masthead (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921251001
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  • 98
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    Sterische Cyclopentadienyl-Äquivalente in der Chemie der f-Elemente: Monomere, homoleptische Lanthanid(III)-tris[N,N′-bis(trimethylsilyl)-benzamidinate] (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2171-2181 
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    ISSN: 0009-2940
    Keywords: Lanthanides ; Benzamidinate ligands ; Steric cyclopentadienyl equivalents ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Steric Cyclopentadienyl Equivalents in f-Element Chemistry: Monomeric, Homoleptic Lanthanide(III) Tris[N,N′-bis(trimethylsilyl)benzamidinates]Anhydrous lanthanide trichlorides react with N-silylated sodium benzamidinates, Na[4-RC6H4C(NSiMe3)2], (1a-d), to give the monomeric, homoleptic lanthanide(III) benzamidinates [4-RC6H4C(NSiMe3)2]3Ln (2-23, R = H, MeO, CF3, Ph). The molecular structure of [4-MeOC6H4C(NSiMe3)2]3Pr (11) has been determined by X-ray diffraction. Absorption and emission measurements reveal that the three benzamidinate ligands produce an unusually large crystal field which is comparable with that of cyclopentadienyl.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921251003
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  • 99
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    Synthese und Struktur eines neuen Bis[(trimethylphosphan)titanocen]-Komplexes mit einer verbrückenden C2-EinheitHerrn Professor Wolfgang Beck zum 60. Geburtstag gewidmet. (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2209-2212 
    Details
    ISSN: 0009-2940
    Keywords: Titanocene complexes ; Cyclopropane, methylene, complexes ; Bis(titanocenyl)acetylene complex ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Structure of a New Bis[(trimethylphosphan)titanocene] Complex with a Bridging C2 Unit
    Notes: Bis(trimethylphosphane)titanocene (1) reacts with 2-methylene-1,1-diphenylcyclopropane (2) to give red crystalline (η2-2-methylene-1,1-diphenylcyclopropane)(trimethylphosphane)titanocene (3). In solution complex 3 degrades smoothly to form the new Cp2Ti(PMe3) - C2 - Ti(PMe3)Cp2 complex 4, the crystal structure of which has been elucidated by an X-ray analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921251007
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  • 100
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    Mixed amide thiolate complexes of zinc with low coordination number at the metal atom (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2199-2207 
    Details
    ISSN: 0009-2940
    Keywords: Zinc complexes ; Low coordination ; Amide complexes ; Thiolate complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three different thiophenoles 2,4,6-(CF3)3C6H2SH (4), 2,4,6-(iPr)3C6H2SH (5), and 2,6-(Me3Si)2C6H3SH (6) with bulky sub-stituents in ortho position were treated with Zn[N(SiMe3)2]2 (7) in a non-coordinating solvent like CH2Cl2 or toluene to yield mixed amide thiolate zinc complexes Zn2[N(SiMe3)2]{S[2,4,6-(CF)3C6H2]}3 (8), Zn3[N(SiMe3)2]2{S[2,4,6-(iPr)3C6H2]}4 (9), and Zn2{S[2,6-(Me3Si)2C6H3]}4 (10), respectively. These compounds comprise low-coordinated zinc atoms. Initially, the reactions were performed in a 1:1 ratio of the reactants. However, in no reaction the expected {Zn[N(SiMe3)2](SR)}x (X = 1,2,3…) species were obtained but compounds which are richer in thiolate substituents (SR/NR2 〉 1) even if a large excess of amide 7 was used. Distinct from these, the reaction between 7 and 2,6-(iPr)2C6H3OH (14) in a 1:1 ratio afforded indeed dimer Zn2[N(SiMe3)2]2{O[2,6-(iPr)2C6H3]}2 (15). The molecular structures of 8, 9, 10, and 15 in the crystal are elucidated by X-ray structural analyses and compared with proposed structures in solution based on multinuclear NMR experiments.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921251006
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