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  • 1
    Electronic Resource
    Electronic Resource
    Preparation and properties of dimethyl phosphonomethyl methylsiloxane dimethylsiloxane copolymers (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 1967-1978 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dimethyl phosphonomethylheptamethylcyclotetrasiloxane (II) and 1, 3-bis(dimethyl phosphonomethyl)tetramethyldisiloxane (III) have been prepared by Arbuzov reaction of trimethyl phosphite with bromomethylheptamethylcyclotetrasiloxane (I) and 1, 3-bis(bromomethyl)tetramethyldisiloxane, respectively. Dimethyl phosphonomethylmethylsiloxane dimethylsiloxane copolymers have been prepared by acid-catalyzed ring-opening polymerization of II with hexamethyldisiloxane (MM) as an end-capping reagent and by reaction of II with III as an end-capping reagent. Dimethylsiloxane polymers with dimethyl phosphonomethyldimethylsiloxy end groups have been prepared by acid-catalyzed polymerization of octamethylcyclotetrasiloxane (D4) and III. Under these conditions hydrolysis of the dimethyl phosphonate ester groups was a problem. On the other hand Arbuzov reaction of trimethyl phosphite with bromomethylmethylsiloxane dimethylsiloxane copolymer gave a dimethyl phosphonomethylmethylsiloxane dimethylsiloxane copolymer with uniform properties. These polymers have been characterized by 1H-, 13C-, 29Si-, and 31P-NMR spectroscopy. Their molecular weight distributions have been determined by gel permeation chromatography (GPC) and their thermal stability measured by TGA.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1987.080250717
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  • 2
    Electronic Resource
    Electronic Resource
    Addition of chlorofluorocarbene to poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) and poly(1,1-dimethyl-1-sila-cis-pent-3-ene): Characterization of chlorofluorocyclopropanated polymer microstructures by 1H-, 13C-, 19F-, and 29Si-NMR spectroscopy (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 1789-1798 
    Details
    ISSN: 0887-624X
    Keywords: chlorofluorocyclopropanated polymers ; carbosilane polymers ; thermal stability ; synthesis ; characterization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chlorofluorocarbene, generated by the sodium iodide catalyzed decomposition of phenyl(dichlorofluoromethyl)mercury, adds to the carbon-carbon double bonds of poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) (I) and poly(1,1-dimethyl-1-sila-cis-pent-3-ene) (II) to yield poly(3,4-chlorofluoromethylene-1-methyl-1-phenyl-1-sila-cis-pent-3-ene) (CIFC-I) and poly(3,4-chlorofluoromethylene-1,1-dimethyl-1-sila-cis-pent-3-ene) (CIFC-II). Similarly, two series of random partially chlorofluorocyclopropanated polymers have been prepared. The microstructures of these adduct polymers have been determined by 1H-, 13C-, 19F-, and 29Si-NMR spectroscopy. The glass transition temperatures (Tg's) depend on the extent of chlorofluoropropanation of these polymers. These copolymers become less thermally stable as the extent of chlorofluorocyclopropanation increases. © 1993 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080310718
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  • 3
    Electronic Resource
    Electronic Resource
    Magnesium chloride supported catalysts for olefin polymerization. XIX. Titanium oxidation states, catalyst deactivation, and active site structure (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 1499-1514 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A precise method for the determinations of Ti+2, Ti+3 and Ti+4 was developed. The CW-procatalyst before activation contains mostly Ti+4 ions with 6% Ti+3 and 4% Ti+2 ions. Activation with AlEt3 alone at room temperature reduced all the titaniums to lower valence states consisting of 71% Ti+3 and 29% Ti+2. Reduction is incomplete when methyl-p-toluate was present as external Lewis base during activation: at 25°C the distribution of Ti+4 : Ti+3 : Ti+2 is 36% : 25% : 38%; the distribution at 50°C is 37% : 22% : 40%. Aging of the activated catalyst caused little or no changes in the distribution of [Ti+n]; whereas the catalytic activity decays rapidly with aging. The aged catalysts have polymerization activity comparable to the decreased activity of the catalyst during a polymerization. The [Ti+n] was determined for the CW-catalyst during the course of a decene polymerization; they were found to be Ti+4 : Ti+3 : Ti+2 = 30% : 27% : 43%, which did not change with polymerization time. These results suggest that the reducibility of Ti+4 species by AlEt3 or 3AlEt3/MPT to different valence states is predicated by their structures. These species do not undergo further changes in their oxidation states during either aging or polymerization. Their decays probably involve nonreductive metathesis reactions like those known for zirconium alkyls. Possible structures for the stereospecific and nonspecific sites are proposed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080270504
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  • 4
    Electronic Resource
    Electronic Resource
    Image enhancement of polyethersulfone ultrafiltration membrane surface structure for atomic force microscopy (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 167-178 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The surface topography and pore structure of ultrafiltration membranes can be investigated with atomic force microscopy. In this study, it was found that the substitution of ethanol for water as the immersion medium improved the resolution of the fine structure of 10K polyethersulfone ultrafiltration membranes. Pores in the membrane surface from 7 to 9 nm in diameter were measured, which coincides with the range expected for 10,000 molecular weight cutoff (MWCO) ultrafiltration membranes. It is believed that this image enhancement results from increased damping and concomitant noise reduction resulting from the higher viscosity of ethanol in contrast to water.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070460116
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  • 5
    Electronic Resource
    Electronic Resource
    Selectivity and kinetics of epoxy resin-bisphenol a reaction catalyzed by certain guanidine derivatives (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 2415-2426 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The reaction of bisphenol A with a diglycidyl ether of bisphenol A may lead to linear polymers if a selective catalyst is used. Selective catalysts promote linear polymer formation while nonselective catalysts increase the rate of crosslinking. Selectivity in epoxy resin-bisphenol A reactions depends upon the nature of the catalyst used. In order to understand these catalyst-structure relationships better, we measured the effects of catalysts on the rate of polymerization (k1) and the rate of crosslinking (k2) during epoxy resin cures. The knowledge of the ratio k1/k2 aids in the selection of catalysts specific for the linear polymerization of epoxy resins. We related this specificity to catalysts basicity. We found that less basic catalysts tend to give large k1/k2 values, indicating that little crosslinking occurs with these highly selective catalysts. We demonstrated that the linear polymer obtained from epoxy resin polymerized by triethanolamine, a very selective catalyst, and the linear polymer prepared using 3-p-chlorophenyl-1,1-dimethylurea, a catalyst with low selectivity, are essentially the same. Finally, we caution that quantitative comparisons of selectivity should be restricted to those reactions whose kinetic reaction orders are the same.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1973.070170808
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  • 6
    Electronic Resource
    Electronic Resource
    2,3-Dialkynyl-1,4-diazabuta-1,3-dienes as Novel π-Systems: Synthesis, Structure, and Electronic Properties (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 205-214 
    Details
    ISSN: 1434-193X
    Keywords: Alkynes ; Cyclic voltammetry ; Diazabutadienes ; Electronic structure ; UV/Vis spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The introduction of alkynyl groups into the 2,3-positions of the 1,4-diazabuta-1,3-diene (DAD) backbone succeeds along two complementary synthetic routes either by condensing triisopropylsilyl-terminated dialkynyl-1,2-diones with primary aromatic amines or by a palladium-mediated alkynylation of bis(imidoyl chlorides). X-ray crystallographic analyses of two dialkynyl DAD derivatives reveals their planar (E-s-trans-E) conformations in the solid state. However, the central CC bond of both DAD backbones investigated has a length of 1.491(2) Å, and is therefore too long to indicate efficient delocalization across the DAD core. The UV/Vis spectra of dialkynyl DADs demonstrate that their absorptions in comparison to those of non-alkynyl DADs are bathochromically shifted by more than 40 nm, thereby demonstrating the suitability of the title compounds for developing NIR chromophores. The electron absorption properties of differentially N,N′-disubstituted dialkynyl DADs gave no indication for a push-pull effect across the DAD skeleton and suggest the ynimine moiety as the active chromophore of dialkynyl DADs. The electrochemical properties of the title compounds were determined by cyclo- and steady state voltammetry and show that introducing alkynyl groups leads to more easily reducible DAD systems. Again, the perception of dialkynyl DADs as covalently linked, but electronically decoupled ynimine units is corroborated by the redox potential of a differentially N,N′-disubstituted dialkynyl DAD. Similar conclusions were drawn from semiempirical MO (PM3) calculations of dialkynyl DADs.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and Structure of the First Carbyne Complex Functionalized Zwitterionic α-Carbenium Phosphinates [Tp′(CO)2M ≡ C-P(O)2-C(NR2)2] (M = Mo, W; R = Me, Et) (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 579-582 
    Details
    ISSN: 1434-1948
    Keywords: Carbyne complexes ; Molybdenum complexes ; Oxidations ; Tungsten ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidation of the phosphaalkenyl-substituted carbyne complexes [Tp′(CO)2M≡C-P=C(NR2)2] (1a: M = Mo, R = Me; 1b: M = W, R = Me; 2a: M = Mo, R = Et; 2b: M = W, R = Et) with molecular dioxygen cleanly affords the orange carbyne complexes [Tp′(CO)2M≡C-P(O)2C(NR2)2] [3a: M = Mo, R = Me; 3b: M = W; R = Me; 4a: M = Mo, R = Et; 4b: M = W, R = Et; Tp′ = HB(3,5-Me2HC3N2)3], which are functionalized at the methylidyne carbon atom by an α-carbenium phosphinate moiety. The novel compounds have been characterized by IR, 1H-, 13C-, and 31P-NMR spectroscopy. In addition, the molecular structure of 4a has been determined by a single-crystal X-ray structure analysis.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis, Structure and Reactivity of 3,4-Dihydro-2H-1,2,4,3-triazaboroles (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1193-1198 
    Details
    ISSN: 1434-1948
    Keywords: Boron ; Triazaboroles ; Heterocycles ; Halogens ; Cyanides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,4-Dihydro-2,4-diphenyl-2H-1,2,4,3-triazaboroles 3a, 3b, and 4 were synthesized by cyclocondensation of N1,N3-diphenylformamidrazone (1) with dibromophenylborane, dibromomethylborane, and boron trichloride. 3-Chloro-3,4-dihydro-2,4-diphenyl-2H-1,2,4,3-triazaborole (4) was converted into 3,4-dihydro-2,4-diphenyl-2H-1,2,4,3-triazaborole (5) by treatment with LiAlH4. The corresponding 3-cyanato and 3-cyano derivatives 6 and 7 resulted from the reaction of 4 with AgOCN and AgCN, respectively. Compound 7 was transformed into the bis(1,2,4,3-triazaborolyl)oxane 8 by silver oxide. Compounds 1-8 were characterized by elemental analyses and spectroscopic methods (1H, 11B, and 13C NMR; IR; MS). The molecular structure of 8 was established by single-crystal X-ray diffraction analysis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Reactivity of Carbonyl-Functionalized Phosphaalkenes RC(O)P=C(NMe2)2 (R = tBu, Ph) towards Electrophiles (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2369-2381 
    Details
    ISSN: 1434-1948
    Keywords: Alkylation ; Carbonyl complexes ; Lewis acids ; Phosphaalkenes ; Protonation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of the carbonyl-functionalized phosphaalkenes RC(O)P=C(NMe2)2 [R = tBu (2a), Ph (2b)] with protic acids and alkylating reagents occurred at the two-coordinate phosphorus atom to give the phosphanyl-substituted carbocations 3a,b and 4a,b. In contrast, treatment with Me3SiOSO2CF3 resulted in attack at the oxygen atom by the silyl group, and the formation of [RC(OSiMe3)=PC(NMe2)2]SO3CF3 (5a,b). Similarly, the Lewis acids B(C6F5)3, Al(tBu)2Cl and AlMe3 were ligated to the oxygen atom of the carbonyl group. Two equivalents of GaMe3 were added to the oxygen and phosphorus atom of the phosphaalkene to yield the thermolabile complexes [RC(OGaMe3)=P(GaMe3)C(NMe2)2] (10a,b). In contrast, one molecule of InMe3 was bound to the phosphorus center of the phosphorus compound. Reaction of the phosphaalkenes with [Ni(CO)4], [Fe2(CO)9] or [{(Z)-cyclooctene}Cr(CO)5] also took place at the pnictogen atom, resulting in complexes of the type [RC(O)P{M(CO)n}C(NMe2)2] (R = tBu, Ph; M = Ni, n = 3; Fe, n = 4; Cr, n = 5). The chemical transformations reported here underline the versatile chemistry of phosphaalkenes and emphasize a relationship between carbonyl-functionalized phosphaalkenes and the well-investigated class of phosphorus ylides. X-ray structures of compounds 6b, 7b*, 10a, 11a and 12a are reported.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Ring-Chain Equilibrium between an [18]Cyclacene Derivative and a Ladder Oligomer (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 99-105 
    Details
    ISSN: 1434-193X
    Keywords: Ladder polymers ; Macrocycles ; Cycloadditions ; Retro Diels-Alder reaction ; Benzo[c]furan ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the AB-type Diels-Alder (DA) monomer 12 is reported whose self-condensation leads to the formation of the linear ladder oligomer 17 and its cyclic congener 18. 18 is the largest [n]cyclacene derivative known (n = 18) and can be obtained by thermal treatment of 17 in yields of up to 45% utilizing the reversibility of the DA cyclization involved. 17 can be considered a “storage form” for 18.
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