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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis, Electrochemistry, and Oxygen-Atom Transfer Reactions of Dioxotungsten(VI) and -molybdenum(VI) Complexes with N2O2 and N2S2 Tetradentate Ligands (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 313-321 
    Details
    ISSN: 1434-1948
    Keywords: Tungsten complexes ; Molybdenum complexes ; Tetradentate ligands ; Oxygen-atom transfer ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of N2O2 tetradentate ligands with a range of substituents attached to the nitrogen atoms have been prepared (H2Ln) (n = 1-9). Treatment of these ligands and the N2S2 tetradentate ligand H2L10 with [WO2Cl2(DME)] (DME = 1,2-dimethoxyethane) in the presence of triethylamine leads to the formation of cis-dioxotungsten(VI) complexes [WO2(Ln)] (n = 1-10). Reaction of the N2O2 tetradentate ligands H2Ln (n = 1, 3-7) with ammonium molybdate tetrahydrate and dilute hydrochloric acid gives the corresponding molybdenum(VI) analogs [MoO2(Ln)] (n = 1, 3-7). These compounds have been spectroscopically characterized and the molecular structures of [WO2(Ln)] (n = 1, 2, 9) and [MoO2(L5)] have been established by X-ray diffraction analysis. These high-valent compounds participate in oxygen-atom transfer reactions and can catalyze the oxidation of benzoin with dimethyl sulfoxide. The complex [WO2(L10)], which contains an S-donor ligand, has lower reduction potential and higher reactivity toward oxo-transfer reactions than analogous tungsten complexes having N2O2 ligands. The kinetics of these catalytic processes along with the structure and electrochemistry of these dioxotungsten and -molybdenum complexes are described and compared.Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2005/1999/98246_s.pdf or from the author.
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and Chemistry of Dithiadiazole Free Radicals [4-(4′-C5H4N)CN2S2] and [4-(3′-C5H4N)CN2S2]; X-ray Crystal Structures of [Pd3{μ-SNC(Ar′)NS-S,S′}2(PPh3)4] (Ar′ = 4′-C5H4N, 4′-C5H4NBEt3 and 3′-C5H4NBEt3) (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 1045-1054 
    Details
    ISSN: 1434-1948
    Keywords: Palladium ; Dithiadiazole ; Radicals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new 1,2,3,5-dithiadiazoles, [4-(4′-C5H4N)CN2S2] (L1) and [4-(3′-C5H4N)CN2S2] (L2), with different pyridyl groups at the 4-position were prepared. As Lewis bases, the dithiadiazoles reacted with Lewis acids via their pyridyl groups to form acid-base adducts with retention of the five-membered dithiadiazole ring. Ligands L1 and L2 reacted with excess triethylborane to give L1BEt3 and L2BEt3 (1a and 1b) and with Mn(CO)5Br to give the fac-Mn(CO)3Br(L1)2 (2a) and fac-Mn(CO)3Br(L2)2 (2b) complexes. When reacted with Pd0 complexes, namely, Pd(PPh3)4 and a mixture of [Pd2(dba)3] and dppf, the dithiadiazoles underwent ring-opening reaction by reductive cleavage of the S-S bond of the dithiadiazole ring. The resulting formation of Pd-S bonds gave the corresponding trinuclear complexes [Pd3{μ-SNC(4′-C5H4N)NS-S,S′}2(PPh3)4] (3a), [Pd3{μ-SNC(3′-C5H4N)NS-S,S′}2(PPh3)4] (3b), and [Pd3{μ-SNC(4′-C5H4N)NS-S,S′}2(dppf)2] (4) [dba = dibenzylideneacetone, dppf = 1,1′-bis(diphenylphosphanyl)ferrocene]. Complexes 3a and 3b reacted with excess triethylborane to give the corresponding acid-base adducts [Pd3{μ-SNC(4′-C5H4NBEt3)NS-S,S′}2(PPh3)4] (5a) and [Pd3{μ-SNC(3′-C5H4NBEt3)NS-S,S′}2(PPh3)4] (5b.) Complex 3a reacted with Mn(CO)5Br to give {[Pd3{μ-SNC(4′-C5H4N)NS-S,S′}2(PPh3)4][MnBr(CO)3]}n (6). The structures of 3a, 5a, and 5b were established by X-ray crystallography.
    Additional Material: 3 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    A Novel Palladium-Catalyzed Asymmetric Cyclocarbonylation of Allylic Alcohols to γ-Butyrolactones (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 417-423 
    Details
    ISSN: 0947-6539
    Keywords: asymmetric synthesis ; butyrolactones ; carbonylations ; catalyst system ; palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A catalyst system based on [Pd2(dba)3]·CHCl3/(-)-BPPM has been found to effect asymmetric cyclocarbonylation of certain prochiral allylic alcohols to produce good yields of optically enriched γ-butyrolactones. The reaction was performed under an atmosphere of H2 (400 psi) and CO (400 psi) at 100°C in methylene chloride for 48 hours. Asymmetric cyclocarbonylation of allylic alcohols with aliphatic substituents proceeded with moderate enantioselectivities (ee = 25-43%). However, enantiomeric excesses of up to 83% were obtained for substrates containing aromatic substituents, in which case the ee was found to be more sensitive to steric, rather than to electronic factors. Recrystallization of the lactones containing an aromatic group from a mixture of CH2Cl2/Et2O/hexanes (0.5/1.0/8.5), by slow evaporation of the solvent or at low temperature, improved the enantiopurities to 〉98% ee on a reproducible basis. The asymmetric center of the aromatic lactones was assigned the (S)-configuration based on the X-ray crystal structure analysis of enantiopure (S)-(+)-3,3-dimethyl-2-(2′-methylphenyl)-γ-butyrolactone (2k). A hydridopalladium intermediate is believed to play a key role in this reaction. Enantioselectivity is thought to be brought about by the preferential formation of 6b. The carbon skeleton of 6b fits into the chiral scaffold of (-)-BPPM.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030313
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  • 4
    Electronic Resource
    Electronic Resource
    Essential work of fracture and j-integral measurements for ductile polymers (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 785-793 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In the ductile tearing of polymers that neck before failure it is shown that the specific essential fracture work (we), consisting of the energies dissipated in forming and tearing the neck, is a material property for a given sheet thickness and is independent of specimen geometry. Work of fracture experiments using both double deep-edge notched (DENT) and deep-center notched tension (DCNT) geometries with different ligament lengths yielded almost identical we values for a grade of high-density polyethylene. These measurements for we are in fairly good agreement with the theoretical values based on the J integral evaluated along a contour surrounding the neck region near the crack tip. Under J-controlled crack growth conditions, it is shown that Jc obtained by extrapolation of the JR curve to zero crack growth and the slope dJ/da are identical, respectively, to we and 4βwp obtained from the straight line relationship between the specific total work of fracture (wf) and ligament length (l).
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1991.090290702
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  • 5
    Electronic Resource
    Electronic Resource
    The radical anion of 1,2:9,10-dibenzo[2.2]paracyclophane.Denoted in [1] as 1,2:7,8-dibenzo[2.2]paracyclophane.. An ESR, ENDOR, and TRIPLE resonance study (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 79-90 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radical anion of 1,2:9,10-dibenzo[2.2]paracyclophane (3) has been studied by ESR, ENDOR, and TRIPLE resonance spectroscopy under a variety of experimental conditions. The coupling constants of the eight protons in the deck-benzene rings, and of the four inner and four outer protons in the side-benzene rings are 0.234, 0.123, and 0.036 mT, respectively (solvent: 1,2-dimethoxyethane; counterion: K+). All three values have the same sign which is predicted to be negative. Comparison of the largest coupling constant (0.234 mT) with the corresponding value (0.297 mT) for the radical anion of the parent [2.2]paracyclophane (1) points to similar nodal properties of the singly occupied orbitals in \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document}. Notwithstanding this similarity, \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document} seems to associate less readily than \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document} with alkali metal counterions, since tight ion pairs of \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document} with K+ are formed only in solvents of low solvating power. Effects of conformational changes on the ESR spectra, such as those previously observed for the radical anion of [2.2]paracyclophane-1,9-diene (2), are not apparent for \documentclass{article}\pagestyle{empty}\begin{document}$ 3^{\scriptstyle {{\relbar}\kern-4pt {.}}} $\end{document} in the temperature range of investigation. Hyperfine data are also reported for the radical anion of a derivative 4 which has a CH3 substituent in one of the side-benzene rings of 3.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700110
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  • 6
    Electronic Resource
    Electronic Resource
    Wavelet and multiple scale reproducing kernel methodsThis is an extended version of a paper presented at the 2nd Japan-U.S. Symposium on Finite Element Methods in Large-Scale Computational Fluid Dynamics, Tokyo, 14-16 March 1994. (1995)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 21 (1995), S. 901-931 
    Details
    ISSN: 0271-2091
    Keywords: wavelet ; multiple scale methods ; optimal dilation parameter ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Multiple scale methods based on reproducing kernel and wavelet analysis are developed. These permit the response of a system to be separated into different scales. These scales can be either the wave numbers corresponding to spatial variables or the frequencies corresponding to temporal variables, and each scale response can be examined separately. This complete characterization of the unknown response is performed through the integral window transform, and a space-scale and time-frequency localization process is achieved by dilating the flexible multiple scale window function. An error estimation technique based on this decomposition algorithm is developed which is especially useful for local mesh refinement and convergence studies. This flexible space-scale window function can be constructed to resemble the well-known unstructured multigrid and hp-adaptive finite element methods. However, the multiple scale adaptive refinements are performed simply by inserting nodes into the highest wavelet scale solution region and at the same time narrowing the window function. Hence hp-like adaptive refinements can be performed without a mesh. An energy error ratio parameter is also introduced as a measure of aliasing error, and critical dilation parameters are determined for a class of spline window functions to obtain optimal accuracy. This optimal dilation parameter dictates the number of nodes covered under the support of a given window function. Numerical examples, which include the Helmholtz equation and the 1D and 2D advection-diffusion equations, are presented to illustrate the high accuracy of the methods using the optimal dilation parameter, the concept of multiresolution analysis and the meshless unstructured adaptive refinements.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650211010
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  • 7
    Electronic Resource
    Electronic Resource
    Enhancement of field desorption mass spectra of alkali metal salts by polyhydroxyl additives (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 9 (1982), S. 72-73 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Field desorption (FD) mass spectra of alkali metal salts of organic acids are characterized by fluctuating ion current, high anode temperature, high abundance of metal ions and low abundance of structurally significant organic ions. As part of a continuing study of matrix effects on the FD process, we have now found that addition of pentaerythritol or cis-inositol results in a smoother desorption and a marked enhancement of intensity in a variety of such spectra. Results are presented for 12-hydroxystearic acid sodium salt; anthraquinone-2-sulfonic acid sodium salt.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200090206
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  • 8
    Electronic Resource
    Electronic Resource
    Langmuir-Blodgett films of rigid rod oligoimides on gold: An x-ray photoelectron spectroscopy study (1992)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 18 (1992), S. 163-172 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Angular-resolved x-ray photoelectron spectroscopy (ARXPS) was used to study mono- and multilayer films of rigid oligoimides prepared on gold-coated glass slides by the Langmuir-Blodgett (LB) horizontal lifting technique. The experimentally obtained total atomic ratios were in a good agreement with molecular formulae. The attenuation of the substrate Au 4f photoemissio intensities was recorded as a function of both the number of LB dips and the take-off angles. The ratio of the thickness to the attenuation length was determined for three different oligoimides from the slopes of the linear attenuation regions. Interpretation of the thickness/attenuation length ratio was based on the models for the oligoimide LB films of oriented structures. The average tilt angle and the area/molecule used in modeling the oligoimide film structures were determined in independent experiments involving grazing angle infrared (GIR) spectroscopy, electrochemistry and LB pressure-area isotherms. The thicknesses of the oligoimide films were calculated from the models and used to derive the value of the attenuation length from the ARXPS slopes. The attenuation length value for Au 4f core-level photoelectrons (Ek = 1169.6 eV) was estimated to be 66-70 Å in the LB films of all three different oligoimides.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740180218
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  • 9
    Electronic Resource
    Electronic Resource
    Temporal control of urate oxidase activity during development of the third-instar larva of Drosophila: The role of 20-hydroxyecdysone (1982)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 3 (1982), S. 215-233 
    Details
    ISSN: 0192-253X
    Keywords: urate oxidase ; 20-hydroxyecdysone ; Drosophila melanogaster ; Malpighian tubules ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The tissue-specific enzyme urate oxidase is confined exclusively to the Malpighian tubules of Drosophila melanogaster and expressed only in the third-instar larva and the adult. Shortly before pupariation urate oxidase activity declines precipitously and is not detectable 24 hours later. That 20-hydroxyecdysone is the factor that triggers the disappearance of urate oxidase activity in late third-instar larvae is demonstrated using the temperature sensitive mutant ecd1 which at the nonpermissive temperature of 29°C fails to accumulate a sufficient concentration of 20-hydroxyecdysone necessary for puparium formation and thus remains a third-instar larva for 1 to 2 weeks before death. Both the life cycle and the temporal profile of urate oxidase activity in ecd1 larvae at 19°C is identical to that of the wild type. However, at 29°C ecd1 third-instar larvae retain high urate oxidase activity. A precipitous decline in urate oxidase activity is observed when ecd1 larvae at 29°C are fed 20-hydroxyecdysone. These data implicate 20-hydroxyecdysone in the process that controls the rapid decline of urate oxidase activity at the time of puparium formation. In whole homogenates of Malpighian tubules, the urate oxidase polypeptide was identified in SDS-polyacrylamide gels by its Rf with respect to homogeneously pure Drosophila urate oxidase and also by immunoprecipitation with rabbit anti-Drosophila urate oxidase IgG. Throughout development the amount of the urate oxidase polypeptide is correlated with the magnitude of urate oxidase activity.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020030305
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  • 10
    Electronic Resource
    Electronic Resource
    Determination of reaction variables for the starch xanthide encapsulation of pesticidesThis article reports the results on research only. Mention of a pesticide in this article does not constitute a recommendation for use by the U.S. Department of Agriculture nor does it imply registration under FIFRA as amended. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned. (1983)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 121-140 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optimization of reaction variables such as xanthation and oxidation conditions was determined for the encapsulation of EPTC (S-ethyl dipropylthiocarbamate) and butylate (S-ethyl diisobutylthiocarbamate) in a crosslinked starch xanthide matrix. Sonification of EPTC and butylate emulsifiable concentrates before encapsulation decreased the size of the cells within the matrix and increased pesticide retention. Pesticide release from the matrix as determined using a constant temperature-humidity chamber showed that low-xanthation and sonified encapsulated products gave the slowest pesticide release.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1983.170210113
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