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  • General Chemistry  (120)
  • 2010-2014
  • 2000-2004
  • 1995-1999  (120)
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  • 1999  (21)
  • 1997  (99)
  • 1
    Electronic Resource
    Electronic Resource
    A Dimeric Tetranuclear Copper(II) Compound Assembled through Pentacoordinating Carbonate Anions (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 505-507 
    Details
    ISSN: 1434-1948
    Keywords: Macrocycle ; Pyrazole ; N-Heterocycle ; Carbonate ; Copper ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 22-membered macrocycle, spanning four endocyclic pyrazole groups, viz. 1,4,9,14,17,22,27,28,29,30-decaaza-5,13,18,26-tetramethylpentacyclo[24.2.1.14,7.111,14.117,20]triacontane-5,7(28),11(29),12,18,20(30),24(27),25-octaene (22Pz), rendered the tetranuclear compound [Cu4(22Pz)2(CO3)2(MeOH)2](ClO4)4(MeOH)4. The copper(II) ions are in distorted octahedral N3O3 environments. All four pyrazole groups of each macrocycle participate in the coordination of the copper(II) ions. The cationic part of this compound is in fact a dimer of two macrocyclic ligands, each containing two copper(II) ions bridged by two carbonate ions in the highly unusual pentacoordinating fashion.Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2005/1999/98332_s.pdf or from the author.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Nucleophilic Aromatic Substitution of Hydrogen in the Reaction of tert-Alkylamines with Nitrosobenzenes - Synthesis and NMR Study of N-(tert-Alkyl)-ortho-nitrosoanilines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 29-35 
    Details
    ISSN: 1434-193X
    Keywords: Nitrosobenzenes ; ortho-Nitrosoanilines ; 2-Nitroso-1,3-phenylenediamines ; Nucleophilic aromatic substitution ; Oxidative nucleophilic substitution of hydrogen ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The reaction of primary amines bearing tertiary alkyl groups (e.g. R-NH2; R = tBu, 1-adamantyl) with nitrosobenzenes has been found to proceed by oxidative nucleophilic aromatic substitution of hydrogen, thereby affording N-(tert-alkyl)-ortho- and -para-nitrosoanilines. The replacement of hydrogen proceeds more rapidly than the replacement of ortho- or para-nitro or -bromo substituents. With p-nitronitrosobenzene, both ortho-hydrogen atoms are substituted to afford N,N′-di(tert-alkyl)-4-nitro-2-nitroso-1,3-phenylenediamines 8a,b. The addition of oxidizing agents (e.g. MnO2) increases the yield of products. 1H-, 13C-, 14N- and 15N-NMR studies have confirmed the structures of the compounds under investigation. In ortho-nitrosoanilines, the rotamer with the nitroso group syn to the amino group is favored.
    Additional Material: 3 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    [(TptBu, Me)CrR]: A New Class of Mononuclear, Coordinatively Unsaturated Chromium(II) Alkyls with cis-Divacant Octahedral Structure (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1668-1674 
    Details
    ISSN: 0947-6539
    Keywords: alkenes ; chromium ; cis-divacant octahedral geometry ; polymerizations ; tris(pyrazolyl)borate complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of CrCl2 with TptBu, MeK yielded [TptBu, MeCr(3-tBu, 5-MepzH)Cl] (1) and [TptBu, MeCrCl] (2), while the same reaction in the presence of pyridine gave 1 and [TptBu, MeCr(py)Cl] (3). Alkylation of 3 with Grignard reagents produced the chromium(II) alkyls [TptBu, MeCrR] (4, R = Et; 5, R = Ph; 6, R = CH2SiMe3), which reversibly added to pyridine to form the five-coordinate adducts [TptBu, MeCr(py)R] (7, R = Et; 8, R = Ph; 9, R = CH2SiMe3). 1, 2, 4, and 5 were structurally characterized by X-ray diffraction. The four-coordinate molecules 2, 4, and 5 adopt a highly unusual cis-divacant octahedral coordination geometry, while 1 is the first five-coordinate TptBu, Me-complex of a first-row transition metal. Despite their coordinative unsaturation, chromium alkyls 4-6 do not polymerize ethylene, or even react with it. This observation is inconsistent with the catalytic activity commonly ascribed to divalent chromium in heterogeneous polymerization catalysts. Attempts to oxidize 4-6 (e.g., with [Cp2Fe]BPh4) to cationic chromium(II) alkyls failed, yielding [TptBu, MeCr(thf)][BPh4] (10) instead.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031016
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  • 4
    Electronic Resource
    Electronic Resource
    N-Substituted 1-Aminoindoles from Electrogenerated N-Substituted 2-(ortho-Nitrosophenyl)ethylamines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 419-430 
    Details
    ISSN: 1434-193X
    Keywords: Electrochemistry ; Electrosynthesis ; Nitrosobenzenes ; Nitrogen heterocycles ; 1-Aminoindoles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -An electrochemical methodology offering efficient access to N-alkyl- and N-aryl-substituted 1-aminoindoles has been developed. N-Substituted 2-(ortho-nitrosophenyl)ethylamines, electrogenerated in a “redox” flow cell, undergo intramolecular cyclization to hydrocinnoline-type intermediates. Under slightly basic conditions, these undergo spontaneous ring-contraction to produce the N-substituted heterocycles in good yields. The reactions have been studied in slightly acidic and slightly basic aqueous alcoholic media.
    Additional Material: 11 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Diastereoselective Intramolecular meta Photocycloaddition of Side-Chain-Substituted 5-(2-Methoxyphenyl)pent-1-enes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 463-470 
    Details
    ISSN: 1434-193X
    Keywords: meta Photocycloaddition ; Photochemistry ; Steric hindrance ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Irradiation of a series of 5-(2-methoxyphenyl)pent-1-enes substituted with a hydroxy or trimethylsilyloxy group at the α-, β-, or γ-position of the side-chain yields in all cases meta photocycloadducts, in which the configuration at the substituted carbon atom is mainly endo. This indicates that the diastereoselectivity originates from minimization of steric interactions between the side-chain substituent and the ortho-methoxy group at the arene unit. Hydrogen bonding does not seem to be involved. The introduction of the side-chain substituents also influences the regioselectivity of the addition: The linear to angular adduct ratios are significantly increased compared to the case of the parent compound.
    Additional Material: 3 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    Oligo-2,6-naphthylenevinylenes - New Building Blocks for the Preparation of Photoluminescent Polymeric Materials (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 643-651 
    Details
    ISSN: 1434-193X
    Keywords: Oligomers ; Synthesis design ; Substituent effects ; Luminescence ; Cyclic voltammetry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Synthetic strategies towards appropriate symmetric and unsymmetric functionalization of the naphthalene ring are presented. By means of Knoevenagel and Wittig condensation reactions new fluorescent, differently functionalized oligo(2,6-naphthylenevinylene)s have been synthesized, the presence of terminal aldehyde or bromine substitution opening the way to the incorporation of the fluorescent trimers in a variety of polymeric materials. The effect of substituting the phenylene ring by the more bulky dialkoxynaphthalene system in arylenevinylene-type materials is studied from the structural point of view and the possibility to tune the emission color and the electron affinity through the introduction of naphthylenevinylene and cyano-substituted naphthylenevinylene units is also investigated.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Steric Effects on the Proton-Transfer Equilibria of Ketones, Sulfoxides, and Phenols (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1507-1515 
    Details
    ISSN: 1434-193X
    Keywords: Ketones ; Sulfoxides ; Phenols ; Steric hindrance ; Acidity ; Basicity ; NMR spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The proton-transfer equilibrium of several bases and acids, including some sterically hindered ketones, sulfoxides, and phenols, has been investigated by means of the determination of the thermodynamics of the equilibrium, NMR 13C relaxation measurements, and quantum chemical calculations. The analysis of such data yields information about the steric effects on basicity or acidity and about the underlying reasons for the anomalous behavior of species having a sterically hindered basic or acidic site. Thus, it is demonstrated that the anomalously low basicity of two sterically hindered ketones (tBu2CO and PhCOtBu) is enthalpic in origin and stems from steric hindrance to the solvation of their protonated forms. No such effect is found for analogous sulfoxides, whereas phenols display a more complex behavior.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/1999/99105_s.pdf or from the author.
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  • 8
    Electronic Resource
    Electronic Resource
    An Efficient Synthesis of Bicyclo[3.3.0]oct-2-en-4-ones and 2-Azabicyclo[3.3.0]oct-7-en-6-ones via β-Amino-Substituted α,β-Unsaturated Fischer Carbene Complexes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2025-2031 
    Details
    ISSN: 1434-193X
    Keywords: Fischer carbene complexes, β-amino-substituted, α,β-unsaturated ; Alkoxycyclopentadienes ; Aldol reaction, diastereoselective ; Bicyclo[3.3.0]octenones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formal [3+2] cycloaddition of β-amino-substituted α,β-unsaturated Fischer carbenechromium complexes 2, which are easily prepared in a one-pot procedure from terminal alkynes 1 via an initially formed alkynylidene complex by a Michael-type addition of a secondary amine, with a variety of alkynes 3 afford the 1,2,5-trisubstituted 3-alkoxy-5-dialkylamino-1,3-cyclopentadienes 4 with an acetal-protected aldehyde or ketone carbonyl group in either the 5-substituent R1 or the N-substituent R2. Under acidic conditions, both the enol ether moiety in the 5-membered ring as well as the acetals in the side chains are hydrolyzed, and the resulting cyclopentenones 6 with carbonyl-group containing side-chains undergo facile intramolecular aldol reactions to give bicyclo[3.3.0]oct-2-en-4-ones 8 and 8-azabicyclo[3.3.0]oct-2-en-4-ones 12, respectively, in good to very good yields for most cases.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/1999/99100_s.pdf or from the author.
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  • 9
    Electronic Resource
    Electronic Resource
    Diversity in Complexation of [RhI(cod)]+ and [IrI(cod)]+ by Pyridine-Amine-Pyrrole Ligands (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1581-1592 
    Details
    ISSN: 1434-1948
    Keywords: Rhodium ; Iridium ; N ligands ; Coordination modes ; Polymerizations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexation of [RhI(cod)]+ and [IrI(cod)]+ by the new pyridine-amine-pyrrole ligands Py-CH2-N(R)-CH2-Pyr-H (HLR; R = H, Bzl, Bu) and the corresponding pyridine-amine-pyrrolate ligands [Py-CH2-N(R)-CH2-Pyr]- (LR-; R = H, Bzl, Bu, CH2Py) has been investigated. The neutral ligands HLR (R = H, Bu, Bzl) give [(HLR)MI(cod)]+ (M = Rh, Ir) in which HLR acts as a didentate ligand via the pyridine nitrogen (NPy) and the amine nitrogen (NRamine). The crystal structures of [(HLH)MI(cod)]PF6 (M = Rh: [1]PF6 and M = Ir: [2]PF6) have been determined. Deprotonation of [(HLR)MI(cod)]+ (M = Rh, Ir; R = H, Bzl, Bu) results in the neutral complexes [(LR)MI(cod)] (M = Rh, Ir) of the mono-anionic ligands LR- (R = H, Bzl, Bu). In square-planar [(LH)MI(cod)] (M = Rh: 3, M = Ir: 4), LH- is didentate via NHamine and the pyrrolate nitrogen (NPyr). The X-ray structures of 3 and 4 reveal that in both cases the uncoordinated NPy accepts a hydrogen bond from NHamine. The X-ray structures of [(LBzl)MI(cod)] (M = Rh: 5, M = Ir: 6), show that LBzl- is didentate via Namine and NPyr for M = Rh and tridentate for M = Ir. In solution LBzl- is tridentate for both M = Rh and M = Ir. The neutral complexes [{Py-CH2-N(R)-CH2-Pyr}MI(cod)] (M = Rh, Ir) cannot be oxidised selectively with H2O2. This is in marked contrast to the previously observed selective oxidation of the corresponding cationic complexes [{Py-CH2-N(R)-CH2-Py}RhI(cod)]+. Rhodium complex 5 is an active catalyst for the stereoregular polymerisation of phenylacetylene, whereas iridium complex 6 is inactive.
    Additional Material: 6 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Spontaneous Assembly of a Novel Tetranuclear Ni-Fe Complex by Complete Reshuffling of Ligands and Oxidation States (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 217-219 
    Details
    ISSN: 1434-1948
    Keywords: Nickel ; Iron ; Clusters ; Carbonyl complexes ; S ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Upon reaction of the mononuclear nickel dithiolate complex [Ni(dsdm)] (H2dsdm = N,N′-dimethyl-N,N′-bis(2-sulfanylethyl)ethylenediamine) with K[HFe(CO)4] in ethanol a unique reshuffling of ligands and of oxidation states takes place. This results in the formation of a novel tetranuclear complex [FeII(dsdm)Ni0(CO)3]2, in which a linear array of Ni-Fe-Fe-Ni is formed. The inner core of this complex consists of the dinuclear [Fe(dsdm)]2, and two Ni(CO)3 groups are bound at the periphery through one of the thiolate sulfurs.
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