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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of Homo- and Hetero-Bimetallic Complexes Containing the Ni(C6F5)2 Moiety - Crystal Structure of [(C6F5)2Ni(μ-SPh)2Pd(dppe)] (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1199-1204 
    Details
    ISSN: 1434-1948
    Keywords: Organometallic compounds ; Nickel complexes ; Crystal structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The compound cis-[Ni(C6F5)2(PhCN)2] has been used as the starting material for the preparation of the bimetallic complexes [(C6F5)2Ni(μ-X)2Ni(C6F5)2]2- (X = SCN, OCN, N3), [(C6F5)2Ni(μ-SCN)2Pd(C6F5)2]2-, [(C6F5)2Ni(μ-NCS)2Pd-(dppe)] [dppe = 1,2-bis(diphenylphosphanyl)ethane], and the trimetallic[(C6F5)2Ni(μ-NCS)2Pd(μ-SCN)2Ni(C6F5)2]2-. The mononuclear compounds [(C6F5)2NiLX] (L = PPh3, P(C6H4MeO-p)3; X = SCN, OCN) are obtained by reaction between [(C6F5)2Ni(&μ-X)2Ni-(C6F5)2]2- and L. The treatment of cis-[Ni(C6F5)2(PhCN)2] with [M(SAr)2(dppe)] leads to the formation of the arylthiolate complexes [(C6F5)2Ni(μ-SAr)2M(dppe)] (Ar = Ph, C6H4Me-p, C6H4NO2-p; M = Ni, Pd, Pt). The X-ray diffraction study of [(C6F5)2Ni(μ-SPh)2Pd(dppe)] shows that both metal atoms, Ni and Pd, are coordinated in a slightly distorted square-planar geometry and the μ-thiolato groups are in the syn conformation.
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  • 2
    Electronic Resource
    Electronic Resource
    λ5-Phosphetes, Benzo-λ5-Phosphetes, Naphtho-λ5-Phosphetes: Four-π-, Eight-π-, and Twelve-π-Electron SystemsDedicated to Professor Manfred Regitz on the occasion of his 60th birthday (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 68-74 
    Details
    ISSN: 0947-6539
    Keywords: ab initio calculations ; cyclic ylides ; heterocycles ; phosphorus ylides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A number of possible strategies for the preparation of λ5-phosphetes were tested as follows: cyclopropenium 6 was treated with the lithium salt of diphenylphosphine to give phosphinocyclopropene 7, but 7 did not undergo ring expansion upon photolysis or thermolysis. P-chloro-C—trimethylsilyl-substituted ylide 8b reacted with two equivalents of dimethyl acetylenedicarboxylate to afford phosphinine 13 via a transient λ5-phosphete 12. Addition of aluminum trichloride to P-halogenated ylides 17a-b led to dihydrophosphetium salts 19a-b, which, upon treatment with pyridine, isomerized into the 1, 2-dihydrophosphet-2-ium salts 20a-b. Hydrolysis of derivatives 20a-b cleanly afforded phosphoniums 21 a-b, which reacted with NaN(SiMe3)2 to give rise to the corresponding λ5-phosphetes 22a-b. The benzo-λ5-phosphete 22a underwent ring expansion reactions with dimethyl acetylenedicarboxylate and acetonitrile, leading to benzo-λ5-phosphinine and benzo-1, 4λ5-azaphosphinine in good yields. Derivative 22b was characterized by X-ray crystal structure analysis. Ab initio SCF calculations, IGLO-13C chemical shifts and Δχ for various benzannulated derivatives and phosphorus heterocycles are presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020113
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  • 3
    Electronic Resource
    Electronic Resource
    Equilibria Between Gas and Liquid Phases for Concentrated Aqueous Solutions of Nitric Acid (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 277-285 
    Details
    ISSN: 1434-1948
    Keywords: Nitric acid ; Nitrogen oxides ; Electrochemistry ; Thermodynamics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Calculated diagrams, representing chemical and electrochemical properties of concentrated aqueous nitric acid mixtures, have been drawn for temperatures of 25 °C and 100 °C using vapor pressures and thermochemical data of related gaseous species. Electrochemical measurements have permitted the establishment of an experimental potential scale (referenced to the saturated mercurous sulfate electrode at 25 °C) incorporated in the diagram at 100 °C. These measurements also allowed the determination of the Gibbs free energy of formation of dissolved nitrous acid for various nitric acid solutions at 100 °C, leading to a value of ΔGf(HNO2) = -36.31 kJ mol-1, for the whole nitric acid concentration range.
    Additional Material: 5 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Structural Analyses of Borane and Chloroborane Adducts of 1,3,5-Dithiaza-, -Dioxaza-, -Thiadiaza-, and -Triazacyclohexanes and Their Rearrangement Products, Boracyclohexanes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2063-2068 
    Details
    ISSN: 1434-1948
    Keywords: Borane adducts ; Triazacyclohexanes ; Thiadiazacyclohexanes ; Dioxazacyclohexanes ; Boracyclohexanes ; Rearrangements ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structural and conformational studies performed by 1H-, 11B-, 13C-, two-dimensional, and variable-temperature NMR spectroscopy of borane and chloroborane adducts of 1,3,5-heterocyclohexanes and their rearrangement products, boracyclohexanes, are reported. N-Methyl derivatives gave equatorial N-borane adducts whereas the N-isopropyl derivatives produced the axial borane compounds. Rearrangement reactions of the adducts gave the first examples of chloroboracyclohexanes bearing boron and nitrogen atoms as stable stereogenic centers. BClH2 and BCl2H adducts were found to be more stable towards ring rearrangement than the corresponding N-BH3 analogs.
    Additional Material: 10 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    BHδ--δ+HC Interactions in N-Borane and N-Chloroborane Adducts Derived from 1,3,5-Heterocyclohexanes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2069-2073 
    Details
    ISSN: 1434-1948
    Keywords: Hydridic-protic hydrogen interactions ; Amine boranes ; 1,3,5-Heterocyclohexanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular structures of 5-methyl-1,3-dithia-5-aziniumcyclohexane iodide, 5-chloroborane-5-methyl-1,3-dithia-5-azacyclohexane, 3,5-bis(borane)-3,5-dimethyl-1-thia-3,5-diazacyclohexane, and 1-borane-1,3,5-trimethyl-1,3,5-triazacyclohexane were determined by X-ray diffraction studies. Interactions between hydridic and protic hydrogen atoms are present when the distances between hydridic and protic hydrogen atoms are shorter than 265 pm and angles for B-N-C bonds are smaller than 107.6(3)°. These interactions explain the conformation of the borane adducts in the solid state.
    Additional Material: 4 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Homogeneous and Supported Copper Complexes of Cyclic and Open-Chain Polynitrogenated Ligands as Catalysts of Cyclopropanation Reactions (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2347-2354 
    Details
    ISSN: 1434-1948
    Keywords: Cyclopropanation ; Copper ; N ligands ; Macrocycles ; Supported catalysts ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: CuI and CuII complexes of cyclic and open-chain polyaza compounds have been tested as catalysts in the benchmark cyclopropanation reaction of styrene with ethyl diazoacetate. In general, only small amounts of copper are needed to promote the reaction. The catalytic activity depends on the structure of the ligand, e.g. amine-amides are more efficient than polyamines, and on the oxidation state of copper, CuII being more active than CuI. Given that CuI is the active species, these changes of behavior must be related to the stabilities of the complexes. The nature of the counterion also has a noticeable influence on the catalytic activity, the role of which is discussed. XAS measurements suggest the formation of oligomeric species. Some of the chiral ligands lead to small enantiomeric excesses. Open-chain ligands can easily be supported on organic polymers and their complexes can be used as catalysts. Furthermore, cyclic and acyclic complexes can be supported on clays by cation exchange and the solids obtained tend to promote the reaction with a decrease in the trans/cis ratio.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hydrolysis and Condensation Reactions of Transition Metal Alkoxides: Calorimetric Study and Evaluation of the Extent of Reaction (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1115-1127 
    Details
    ISSN: 1434-1948
    Keywords: Sol-gel process ; Polymers, inorganic ; Transition metal alkoxides ; 17O-NMR spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The behavior of titanium and zirconium alkoxides towards complexation and water addition is analyzed through water titration and calorimetric experiments. A simple model is presented, which allows evaluation of the mean hydrolysis and condensation constants, Kh and Kc, of both pure and complexed transition metal alkoxides in the sol state, through the analysis of consumed water versus initial hydrolysis ratio curves. These constants allow comparison of the extents of the hydrolysis and condensation reactions for sols obtained from several alkoxide precursors. The complexation ratio only affects the condensation constant Kc, whereas the hydrolysis constant Kh remains unchanged. Analysis of the Kh/Kc ratios has shown that in the sol state, silanol Si-OH groups are more stable than the Ti-OH or Zr-OH groups. Moreover, this study has shown that the proton concentration not only affects the kinetics, but also the final composition of the system. Calorimetric studies of the complexation and hydrolysis/condensation reactions have highlighted the role of coordination unsaturation of the transition metal alkoxides in the exothermicity of these reactions, clearly demonstrating that coordination unsaturation is the driving force behind the reactivity of these alkoxides towards nucleophilic species (e.g. water, complexing ligands, polar solvents).
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  • 8
    Electronic Resource
    Electronic Resource
    A New Type of π-Electron Donors with One Dithiole Unit: Substituted 7-(1,3-Dithiol-2-ylidene)-7-hydrobenz[d,e]anthracenes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1239-1247 
    Details
    ISSN: 1434-193X
    Keywords: Ab initio calculations ; Charge-transfer complexes ; Cyclic voltammetry ; π-Electron donors ; Density functional calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -New electron donors 11a-c bearing only one 1,3-dithiole ring conjugated with an acene backbone have been synthesized by Wittig-Horner reactions from 7H-benz[d,e]anthracen-7-one (10) and differently substituted phosphonate esters 9a-c. The donor properties of 11 have been characterized by means of both experimental techniques and quantum chemical calculations. Cyclic voltammetry measurements on the novel compounds predict donor abilities comparable to those of TTF and BEDT-TTF. The voltammograms show a multi-stage redox behaviour with oxidation up to the trication, where the first two oxidation processes take place at very close potentials. These processes have been assigned to a simultaneous oxidation of the dithiole and acene moieties on the basis of DFT/B3-P86/6-31G* theoretical calculations. Whereas the neutral compound and the monocation exhibit butterfly-shaped non-planar structures, the dication is fully aromatic and consists of a closed-shell, singly charged, planar polyacenic unit and a singly charged dithiole ring. The third redox process can be assigned to a second oxidation of the acene unit. The high aromaticity of the dication, coupled with the particular donor ability of the acene unit are shown to be the key factors in accounting for the electrochemical behaviour and the enhanced donor properties of the novel compounds. Theoretical calculations also help to rationalize the UV/Vis data in that they predict the appearance of a low-energy, intramolecular charge-transfer absorption band for the neutral compounds. Stable charge-transfer complexes with a 2:3 (D/A) stoichiometry have been prepared by reaction with the strong acceptors TCNQF4 and DDQ.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    N-Arylation of Pyrrolidino[3′,4′:1,2][60]fullerene: Synthesis under Solvent-Free Conditions and Electrochemistry of New C60-Acceptor Dyads (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 3433-3436 
    Details
    ISSN: 1434-193X
    Keywords: Cyclic voltammetry ; Fullerenes ; Phase-transfer catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several pyrrolidinofullerenes were N-arylated by phase-transfer catalysis in the absence of solvent. The electrochemical behaviour of the novel C60-acceptor dyads was studied by cyclic voltammetry which showed that the nitro groups on the N-phenyl ring have a strong influence on the reduction potential values. Theoretical calculations at the semiempirical PM3 level fully support the experimental redox potential values.
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    The Release of Singlet Oxygen in the Reaction of Dioxiranes with Amine N-Oxides (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2527-2532 
    Details
    ISSN: 1434-193X
    Keywords: Amines ; Amine N-oxides ; Singlet oxygen ; Dioxiranes ; Deoxygenation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactivity of dimethyldioxirane and methyl(trifluoromethyl)dioxirane towards the amine N-oxides 1a-13a and ammonium derivatives 13b-d has been investigated. In the dioxirane oxidation of the tertiary amines and nitrogen heteroarenes, the expected N-oxides are not always formed. Instead, the in situ generated N-oxides are deoxygenated by the dioxirane with the release of singlet oxygen (1O2) at comparable or even higher rates than the amine oxidation. The amount of 1O2 has been quantified by IR chemiluminescence and by chemical trapping with 9,10-dimethylanthracene. The nucleophilicity of the N-oxide determines the efficacy of the 1O2 release in the deoxygenation. Thus, for the less nucleophilic heteroaromatic N-oxides, the deoxygenation of the amine oxide competes ineffectively with the oxidation of the amine. The ammonium derivatives 13b-d do not promote the decomposition of the dioxiranes; as expected, they are epoxidized.
    Additional Material: 2 Tab.
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