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  • 1990-1994  (1,516)
  • 1992  (1,516)
  • Engineering  (757)
  • Inorganic Chemistry  (732)
  • crystal structure  (128)
  • Nuclear reactions
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  • 1990-1994  (1,516)
Year
  • 1
    ISSN: 1572-8862
    Keywords: Manganese ; agostic ; crystal structure ; CH activation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Agostic interactions of CH bonds with metal atoms are currently of great interest. UV irradiation of Mn2(CO)8 (PMe2Ph)2 in the presence of the HC≡COEt yielded the new compound Mn2(CO)6(PMe2Ph)2 [μ-C(OEt)=C(H)C=C(H)C=O(OEt)],1 that contains a strong agostic interaction of an olefinic CH bond to one of the managanese atoms, Mn...C=2.349(5), Mn...H=2.01(4). This interaction can be removed (reversibly) by CO addition (25°C/1000 psi) to1 to yield the new complex Mn2(CO)7(PMe2Ph)2[μ-C(OEt)=C(H)C=C(H)C=O(OEt)],2.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of cluster science 3 (1992), S. 123-144 
    ISSN: 1572-8862
    Keywords: Molybdenum ; tungsten ; crystal structure ; reduction ; acetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Four new compounds having nine cluster electrons and cores of the types Mo3OCl3, Mo3OBr3, and W3OCl3 are reported. Compound (1) prepared by reduction of [Bu4N][Mo3OCl6(OAc)3] in THF with metallic zinc, was shown by X-ray crystallography to be Mo3OCl4(OAc)3 (THF)2 (1). It forms crystals in space groupP21 with unit cell dimensionsa=9.472(2) Å,b=13.546(4) Å,c=9.652(2) Å, β=101.70(2)°,V=1201(1) Å3,Z=2. The [Mo3(μ3-O)(μ-Cl)3]4+ core is surrounded by three μ-O2CCH3 anions, one Cl−, and two THF and has Mo-Mo distances of 2.620(1) Å, 2.613(1) Å, and 2.530(1) Å, with the shortest bond between the two Mo atoms to which the THF molecules are coordinated. Compounds [Bu4N]2 [Mo3OBr6(O2CCH3)3] · Me2CO, (2) and [Mo3OBr3(O2CCH3)3(PMe3)3]3 · BF4, (3) are the first two nine-electron Mo3 species with a [Mo3(μ3-O) Br3]4+ core. Both were obtained by zinc reduction of [Mo3OBr6(O2CCH3)3]− in the presence of (NBu4) Br (2) or PMe3 and NaBF4 (3), and each was characterized crystallographically. Compound (2) crystallized in space group Cc with unit cell dimensionsa=25.037(5) Å,b=12.827(2) Å,c=21.484(4) Å, β=122.96(1)0,V=5790(3) Å3,Z=4. While the anion has no crystallographically required symmetry, its virtual symmetry is C3v . The Mo-Mo distances are 2.619(2) Å, 2.610(3) Å, 2.644(2) Å, with a mean value of 2.624[14] Å. Compound (3) crystallized in space groupP21/c with unit cell dimensionsa=10.846(2) Å,b=25.033(5) Å,c=12.641(5) Å, β=94.74(2)0,V=3420(2) Å3,Z=4. The cation occupies a general position but has virtual C3v symmetry, with Mo-Mo distances of 2.601(2) Å, 2.610(2) Å, 2.627(2) Å, with a mean value of 2.613[14] Å. Thus the anionic and cationic Mo3 clusters in (2) and (3), respectively, have average Mo-Mo distances that are equal within experimental error. Compound (4), [NEt4]2 [W3OCl6(O2CCH3)3] is the first 9-electron compound of this type containing tungsten. It was prepared by reduction of [Et4N][W3OCl6(OAc)3] in benzene with Na/Hg. It crystallized in space groupP212121 with unit cell dimensionsa=11.076(2) Å,b=14.345(2) Å,c=21.026(3) Å,V=3574(1) Å3,Z=4. The anion resides on a general position but has virtual C3v symmetry, with W-W distances of 2.577(1) Å, 2.612(1) Å, 2.584(1) Å and a mean value of 2.591[15] Å.
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  • 3
    ISSN: 1572-8862
    Keywords: Heterometallic-heterobridging cubane-type tetranuclear cluster ; preparation ; crystal structure ; molecular orbital calculation ; quasi-aromaticity ; copper ; molybdenum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract By the reaction of cluster [Mo3OS3](dtp)4(H2O) used as starting material with CuI using [3+1] mode, two novel heterometallic-heterobridging cubane-type tetranuclear cluster compounds [CuMo3OS3]·I·(μ-OAc)[S2P(OC2H5)2]3·L [(I)L=py, (II)L=DMF] [dtp=S2P(OC2H5)2; OAc=OOCCH3] containing [CuMo3OS3] core have been obtained. Compounds (I) and (II) have been characterized by IR, EPR, UV-VIS, electrochemistry and X-ray crystallography. By comparison of these two compounds with the analogous [CuMo3S4] series in the structure and molecular orbital calculation, the influence of mixed S/O bridging on the structure is discussed. It is demonstrated that the {Mo3S3} cluster ring in [Mo3OS3]4+ possesses a similar quasi-aromaticity to [Mo3S4]4+. Crystal data: for (I), space group= $$P\overline 1 $$ ,a=13.781(8)Å,b=14.523(6)Å,c=12.098(6)Å, α=98.37(4)°, β=109.41(5)°, γ=105.00(5)°,V=2133(2)Å3,Z=2,R=0.058; for (II), space group= $$P\overline 1 $$ ,a=13.215(4)Å,b=17.818(8)Å,c=9.873(4)Å, α=106.06(4)°, β=109.78(3)°, γ=82.00(3)°,V=2100(2)Å3,Z=2,R=0.045.
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  • 4
    ISSN: 1572-8951
    Keywords: Non-topochemical reaction ; crystal structure ; lattice energy calculations ; thermal motion analysis ; disorder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The molecular and crystal structure of 2,5-dibenzylidenecyclopent-3-ene-1-one has been studied in detail to explain the formation of a non-topochemical pseudo-mirror-symmetric dimer upon photoirradiation. Packing energy calculations, analysis of the thermal motion, and lattice energy calculations are employed to analyse and understand the observed dimerization reaction, crystal structure, and crystal properties.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Russian chemical bulletin 41 (1992), S. 1076-1079 
    ISSN: 1573-9171
    Keywords: X-ray crystallographic analysis ; 1,1′-divinyl-2,2′-biimidazolyl ; crystal structure ; molecular structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystal and molecular structures of 1,1′-divinyl-2,2′-biimidazolyl (L) were determined by x-ray crystallographic analysis. It was established that the molecule of L has crystallographic symmetry 2 and a cisoid conformation with an angle of rotation of 128° between the imidazole rings. The length of the C2-C2′ bond is increased to 1.485(11) Å compared with the length of the analogous bond in unsubstituted 2,2′-biimidazolyl (1.423 Å). Localization of the N=C multiple bond is observed [1.297(9) Å]. The other N-C bonds of the ring are almost equalized (1.374 Å) and are close to the standard values for bonds of the C sp 2-N type in imidazoles. The angle between the plane of the heterocycle and the plane passing through the atoms of the vinyl group amounts to 7°.
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  • 6
    ISSN: 1573-9171
    Keywords: synthesis ; crystal structure ; UV spectra ; 2,6-di-tert-butyl-4-[α-(2-hydroxy-1-naphthyl)methyl]phenol ; 2,6-di-tert-butyl-4-[α-morpholino-α-(2-hydroxy-6-bromo-1-naphthyl)methyl]phenol ; 2,6-di-tert-butyl-4-α-(2-hydroxy-1-naphthyl)-1,4-methylenequinone ; 2,6-di-tert-butyl-4-α-(2-acetyloxy-1-naphthyl)-1,4-methylenequinone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mannich bases exhibiting photo- and thermochromic properties in solutions were synthesized from 3,5-di-tert-butyl-4-hydroxybenzaldehyde and 2-naphthols. An investigation of an acetyl derivative of methylenequinone, modeling a product of photo- and thermochromic transformations, proved that the color change of solutions of the Mannich bases is due to reversible dissociation into colored methylenequinones and morpholine. On the basis of data of x-ray diffraction analysis of one of the Mannich bases, characteristics of their molecular structure were determined, and reasons were stated for their effect on the dissociation mechanism.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Russian chemical bulletin 41 (1992), S. 1950-1956 
    ISSN: 1573-9171
    Keywords: hexafluorotitanates ; synthesis ; crystal structure ; 19F NMR ; IR spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mixed alkali hexafluorotitanates of the composition LiMTiF6 are synthesized, which crystallize with the orthorhombic symmetry. The lattice parameters of these materials are determined. It is shown that substitution of the Li+ cation in Li2TiF6 by Na+, K+, Rb+, and Cs+ leads to various degrees of distortion of the hexafluoroion. It is determined (19F NMR data) that the change in the dynamic state of the octahedral [TiF6]2− ions is related to their transition from the hindered-rotational to the isotropic state.
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  • 8
    ISSN: 1573-9171
    Keywords: macrocyclic polyethers ; crystal structure ; biological activity ; IR spectra ; complex with calcium thiocyanate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The antihypoxic and anticonvulsant activity of eight new amidophosphoryl derivatives of crown ethers was investigated. It was found that some of them exhibit pronounced antihypoxic activity. The results of an x-ray structural and IR spectroscopic study of dibenzo-N-phenylphosphonyl-14-crown-5 (a=9.818,b=16.062,c=15.925 Å; γ=124.90°;V=2072 Å3;M=417.2;d=1.33 g/cm3 forZ=4, 1955 independent reflections [I〉3σ(I)] in a DAR-UM inCuK α radiation,P2 1/b space group,R=5.2%) and dibenzo-N-adamantylphosphonyl-14-crown-5 compounds (a=11.077,b=15.936,c=16.771 Å; γ=56.05°;V=2456 Å3;M=486.3;d=1.31 g/cm3 forZ=4, 2164 independent reflections [I〉3σ(I)] in a DAR-UM inCuK α radiation,P21/b space group,R=5.1%) are reported. Some details of the structure of the dibenzo-N-phenylphosphonyl-14-crown-5-complex with calcium thiocyanate and water are discussed; a polyhedron with a coordination number of six was found for the first time for calcium complexes with macrocyclic ligands. The combined examination of the results of the biological, x-ray structural, and IR spectroscopic study of macrocyclic, 14-member ligands suggested that the nature of the substituents at phosphorus affect the conformational state of the macrocycle, which remains unchanged in complexation in the investigated conditions.
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  • 9
    ISSN: 1573-9171
    Keywords: crystal structure ; molecular complexes ; phosphinimines ; protonation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract X-ray diffraction analysis has been used to determine the crystal structures of the 1:1-composition products of protonation by perchloric acid of isomeric triphenyl-N-(4-methylpyridyl-2)phosphinimine (1) and triphenyl-N-(3-methylpyridyl-2)phosphinimine (2). The structures were refined toR=0.048 andR=0.052, respectively, using 2274 (1) and 2647 (2) reflections. The protonation centers are located at the sites of N atoms of the pyridine ring (1) and the phosphinimino group (2). The distribution of the bond lengths in the cations suggests that a significant contribution is made by a phosphonic structure with positive charges localized on the P atoms. N-H...O hydrogen bonds, with lengths of 2.890(4) and 3.020(3) Å, connect cations and anions in both structures.
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  • 10
    ISSN: 1573-9171
    Keywords: synthesis ; crystal structure ; 1,12-difluoro-1,1,3,5,5,8,8,10,12,12-decanitro-3,10-diazadodecane-6,7-diol dinitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A two-step synthesis has been proposed to obtain 1,12-difluoro-1,1,3,5,5,8,8,10,12,12-decanitro-3,10-diazadodecane-6,7-diol dinitrate, starting from 1,1,4,4-tetranitrobutane-2,3-diol and N-(methoxymethyl)-2-fluoro-2,2-dinitroethyl-amine, followed by nitration of the Mannich base formed. An x-ray-diffraction investigation of the dinitrate obtained was carried out.
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  • 11
    ISSN: 1573-9171
    Keywords: organic metals ; radical-cation salts ; bis(ethylenedithio)tetrathiafulvalene = ET ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The electrochemical oxidation of ET [bis(ethylenedithio)tetrathiafulvalene] in bromobenzene (electrolyte Bu 4 N[HgBr 3 ]) gave the radical-cation salt (ET) 8 [Hg 2 Br 6 ·PhBr] 2 (1), a new organic metal with a temperature range of 300–125 K. At 125 K a metal—dielectric transition is observed. Crystallographic data for (1):a=19.171(6),b=12.668(4),c=17.777(6) Å, α=118.03(3), β=89.45(2), γ=101.21(3)°, P $$\overline 1 $$ ,Z=1,d calc=2.30 g/cm 3 . The crystal structure of (1) is laminar. In the conducting organic layer the ET radical cations are linked into bands by shortened intermolecular S···S contacts of the “side-to-side” type. The anionic layer consists of centrosymmetric complexes [Hg 2 Br 6 ·C 6 H 5 Br] 2 4− . The Hg 1 and Hg 2 atoms are characterized by a trigonal configuration of the Hg-Br bond which is built up, on account of secondary Hg···Br interactions, into trigonal-bipyramidal for Hg 1 and trigonal-pyramidal (tetrahedral) for Hg 2 . Interaction between the anionic and cationic layers is effected through Br 6 ...S 8 contacts [3.491(7) Å)].
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  • 12
    ISSN: 1573-9171
    Keywords: organic metals ; bis(ethylenedithio)tetrathiafulvalene (ET) ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The composition and structure of the radical-ion salt (ET) 2 [Hg(SCN) 2 Cl], a new organic metal withT M-D=50 K, were established in an x-ray structure investigation. Principal crystallographic data:a=36.69(1),b=8.302(8),c=11.732(8) Å, β=90.02(6)°, space groupCc, Z=4,d calc=2.08 g/cm 3 ,R=0.067. The crystal structure of the salt consists of an alternation of organic (cationic) and inorganic (anionic) layers along the axisa. The anionic layer consists of the polymeric chains in which the [Hg(SCN) 2 Cl]− ions are linked together along the axisc through secondary Hg···N bonds with lengths of 2.75(3) and 2.98(8) Å. On account of these interactions the trigonal configuration of the bonds of the Hg atom is built up to trigonal-bipyramidal. In the organic layer with a structure of the κ type the ET cations form dimers with an interplanar distance of 3.53 Å. ET cations belonging to neighboring dimers are linked together through shortened intermolecular S...S contacts with lengths of 3.40–3.50(2) Å.
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  • 13
    ISSN: 1573-1111
    Keywords: Calix[4]arene ; crystal structure ; second-sphere coordination ; nickel(II) ; copper(II) ; pyridine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The title compounds crystallize such that bilayers of calixarenes are separated by hydrophilic layers. In each case the transition metal has, in addition to a primary sphere of ligands, a second-sphere coordination by a calixarene. [(H2O)5Ni(NC5H5)]2(Na)[calix[4]arene sulfonate]·3.5 H2O,1, crystallizes in the triclinic space groupP $$\bar 1$$ witha = 12.487(4),b = 14.281(2),c = 15.055(5) Å, α = 85.66(2), β = 80.07(2), γ = 80.48(2)°, andD c = 1.64 g cm−3 forZ = 2. Refinement based on 2441 observed reflections led to a finalR value of 0.066. There are two different environments for the nickel-containing cations: one is positioned within the hydrophilic layer with the pyridine ligand intercalated into the hydrophobic calixarene bilayer and the other is also positioned within the hydrophilic layer, but the pyridine ligand is inserted into the hydrophobic cavity of the calix[4]arene. [(H2O)4Cu(NC5HS)2](H3O)3[calix[4]arene sulfonate]·10 H2O,2, crystallizes in the triclinic space groupP $$\bar 1$$ witha = 15.438(4),b = 15.727(6),c = 12.121(9) Å, α = 112.74(4), β = 102.02(4), γ = 85.34(4)°, andD c = 1.57 g cm−3 forZ = 2. Refinement based on 3925 observed reflections led to a finalR value of 0.107. The structure is similar to that of 1 except that the one copper-containing cation spans the hydrophilic layer and is intercalated into the bilayer of calixarenes on one side and positioned into the calixarene cavity on the other.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 14 (1992), S. 55-64 
    ISSN: 1573-1111
    Keywords: Host-guest inclusion compound ; p-,m-,o-xylene ; deoxycholic acid ; symmetry factor ; energy transfer ; photophysical factor ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The isomerization processes induced by UV photons in inclusion compounds of the host-guest type are examined, with special attention to the photophysics of the energy transfer process between the host and the guest, as well as to the influence of the host molecular cavity symmetry and the guest molecular symmetry. In particular, the experimental study has been carried out on the isomerization processes ofp-,m-, ando-xylene inside the molecular cavities of deoxycholic acid. The results have been compared with those obtained by irradiating the xylenes in an inert solution of hexane. The main difference is the elimination of by-products when the photochemical process is carried out in the solid state inclusion compound; however, the high purity of the isomerization product corresponds to a decrease in its yield with respect to the reaction in solution, due to the energy transfer process from the host to the guest moiety.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity 5 (1992), S. 33-38 
    ISSN: 1572-9605
    Keywords: Yttrium ; copper ; X-ray ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Single crystals of Y2Cu2O5 were obtained in the flux growth process by controlled heating of a mixture of Y2O3, BaO, and CuO in a molar ratio of 1∶8∶20. These crystals were analyzed by a single-crystal X-ray diffraction analysis. The crystal contains polymeric chains of Cu2O5 interspersed by yttrium ions surrounded by octahedral arrangements of oxygen atoms. Crystal data: space group=Pna21,a=10.799(2) Å,b=3.4990(5) Å,c=12.459(2) Å,Z=4, 380 reflections,R=0.026,R w=0.030.
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  • 16
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 9-14 
    ISSN: 0009-2940
    Keywords: Alkynyl groups ; Palladium, trimethylphosphane complexes ; Trimerization, oxidative ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidative Trimerization of Alkynyl Groups at Trimethylphosphane Palladium ComplexesAlkynylpalladium halides trans-PdX (C ≡ CR)(PMe3)2 [1, 2, 4, X = Cl, R = SiMe3, (CH2)2CH3, (CH2)5CH3; 3, X = Br, R = (CH2)2CH3] were synthesized by routine methods, while further examples of the series trans-PdX (C ≡ CR)(PMe3)2 [5, 7, 8, 10, X = Br, R = SiMe3, CMe3, (CH2)2CH3, Ph; 7, 9, 11, X = I, R = SiMe3, SiPh3, OEt] and trans-PdX (C ≡ CR)(PPh3)2 (12-14, X=I, R=SiMe3, CMe3, CH2OH) were obtained by oxidative addition of 1-halogeno-1-alkynes to PdL4 (L=PMe3, PPh3). Just above the melting point or decomposition point 5-7 are transformed by oxidative trimerization of the alkynyl groups to give enediynyl complexes trans-PdX[C(C ≡ CR)=C(C ≡ CR)R](PMe3)2 (15, 16, R=SiMe3, X=Br, I; 17, X=Br, R=CMe3). According to an X-ray structure analysis 17 has E configuration.
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 15-22 
    ISSN: 0009-2940
    Keywords: Boranes, trialkyl- ; Nitriles ; Condensation ; β-Diketimines ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of trialkylboranes, e. g. triethylborane (Et3B), tripropylborane (Pr3B), or 9-alkyl-9-borabicyclo[3.3.1]nonane [alkyl-BBN; alkyl=Et, 1-methylpropyl, 1-methybutyl/1-ethylpropyl], with either aceto-, propio-, butyro-, pivalo-, and benzonitrile gives, depending on the reaction conditions used or the nitrile employed, either the substituted diazoniadibora-tetidines (1 a - c), products of partial hydroboration, or by condensation of two or three nitrile molecules, with or without a concomitant hydroboration, the C3BN2 heterocycles 2a - c, 8a/b, 9a - d, and 10a/b (X-ray structure analyses of 2a and 10b).
    Additional Material: 2 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 43-46 
    ISSN: 0009-2940
    Keywords: Helicobacter Pylori ; Bismuth ; (S)-Lactate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metals in Biology and Medicine, III.  -  Bismuth Lactate: Synthesis and Structure of a Hydroxycarboxylate ComplexAs a compound of medical relevance, bismuth (S)-lactate was synthesized and structurally characterized (single-crystal X-ray diffraction). Exploiting the versatile coordination chemistry of carboxylate groups (chelating and bridging ligands), the crystal structure is based upon a three-dimensional network, showing bismuth in a high coordination number environment.
    Additional Material: 3 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 47-53 
    ISSN: 0009-2940
    Keywords: Silyl triflates ; Oligosilanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation of New Monomeric, Oligomeric, and Polymeric Silyl TriflatesThe highly reactive silyl triflates R3SiOSO2CF3 are valuable reagents in organosilicon chemistry. New triflate derivatives of mono- and oligosilanes have been prepared by substitution of phenyl groups or hydrogen atoms for the trifluoromethanesulfonyl group. The presence of the electron-withdrawing triflate group leads to a strong deactivation of the other substituents at the silicon atom, and the displacement of a second phenyl group at the same silicon atom is much slower than the first step. For this reason in the case of phenylated oligosilanes stepwise monosubstitution of the silicon atoms has been found. Other new oligomeric silyl triflates are obtained by reaction of silanediyl(triyl) bis(tris)(trifluoromethanesulfonates) with lithium derivatives of organosilicon compounds. Finally, the cleavage of silicon-phenyl bonds of poly[methyl(phenyl)silanes] by CF3SO3H leads to triflate derivatives of polysilanes.
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  • 20
    ISSN: 0009-2940
    Keywords: Lithium dicyanomethanide ; Sodium dicyanomethanide ; Dicyanomethanides, lithium, sodium, tetrabutylammonium salts ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Crystal Structures of {Li3(12-crown-4)2[HC(CN)2]3}, {Na(15-crown-5)[HC(CN)2]}, and {NaN(nBu)4[HC(CN)2]2 · THF}The preparation and the crystal structures of the title compounds 1 - 3 are described. 1 forms a polymeric chain structure, in which one of the lithium ions is linked by Li…NCC(H)CN… bridges. The remaining lithium ions form (12-crown-4)Li[NCC(H)CN] units, which are coordinated by one of the nitrogen atoms of the dicyanomethanide ions with the lithium ions of the chain. 2 forms an ion pair, in which the sodium ion is coordinated by the five oxygen atoms of the crown ether molecule and by one nitrogen atom of the dicyanomethanide ion. 3 has a threedimensional network, in which the sodium ions are coordinated in a distorted tetrahedral manner by the nitrogen atoms of the dicyanomethanide ions. In the cavities of the network the tetrabutylammonium ions and the THF molecules are found.
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  • 21
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 103-106 
    ISSN: 0009-2940
    Keywords: Alkynes ; Nickel complexes ; Stannenes ; Metallacycloalkenes ; Kinetic and thermodynamic reaction control ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis, Structure, and Reactivity of a Stanna(II)-nickela(III)-cyclobutene KomplexesThe (ethyne)nickel(0) complex (iPr2PC2H4PiPr2)Ni(C2H2) (1) reacts with the stannene Sn[CH(SiMe3)2]2 below -30°C to yield the stanna(II)-nickela(II)-cyclobutene complex (iPr2PC2H4PiPr2)YYNiCH=YYCHSn[CH(SiMe3)2]2 (2; 83%) as the kinetically controlled product; 2 has been characterized by IR and NMR spectroscopy and an X-ray crystal-structure determination. The latter shows the central four-membered ring to be planar with a long Ni - Sn bond [2.626(1) Å]. According to the temperature-dependent NMR spectra, 2 dissociates reversibly in solution to the starting components. The synthesis reaction thus represents an equilibrium as long as the temperature is below 20°C. These observations indicate that the structural lability of the stanna(II)-nickela(II)-cyclobutene moiety is associated with the weakness of the Ni - Sn bond. The bonding situation in 2 is best described as an “inner complex” in which a stannyl anion is coordinated to a nickel(II) cation. An ethereal solution of 2 undergoes an oxidative addition of one ethyne C - H bond to the stannene at 20°C to give the Ni(0)/Sn(IV) complex iPr2PC2H4PiPr2)Ni({η2-HC≡CSn(H)[CH(SiMe3)2]2} (3) as the thermodynamically controlled product. Reaction of 3 with CO liberates the new alkyne ligand.
    Additional Material: 1 Ill.
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  • 22
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 123-123 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 23
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 93-96 
    ISSN: 0009-2940
    Keywords: Diazaphosphiridine oxides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis, Structure, and Isomerization of Diazaphosphiridine OxidesHerrn Professor Joseph Grobe zum 60. Geburtstag gewidmet.The 1,2-Bis(alkyl)iminophosphane, Et3C  -  P=N  -  tBu (1), reacts with nitroso compounds, RNO (R=tBu, Ph), to form the diazaphosphiridine oxides, Et3C  -  YYP(=O)  -  NtBu  -  NYYR, 4a, b. While 4a (R=tBu) is thermally stable, 4b (R=Ph) isomerizes with formation of the benzodiazaphosphole oxide Et3C  -  YYP(= O)  -  NH  -  C6H4  -  NYYtBu (5). The corresponding phospholimine Et3C  -  YYP(=NtBu)  -  NH  -  C6H4  -  NYYtBu (7) has been obtained from 1 and azobenzene. The three-membered phosphorus heterocycle 4a has been characterized by X-ray structure analysis, which reveales some remarkable features.
    Additional Material: 1 Ill.
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  • 24
    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.
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  • 25
    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.
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  • 26
    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.
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  • 27
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 163-169 
    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.
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  • 28
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 243-246 
    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.
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  • 29
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 255-258 
    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.
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  • 30
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 119-121 
    ISSN: 0009-2940
    Keywords: Isocyanide ; Chromium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The triisocyanide ligand CH3C(CH2NC)3 reacts with Cr-(CO)5(THF) depending on the stoichiometry to give the complexes CH3C(CH2NC)x[CH2NC - Cr(CO)5]3-x (x=1, 2). The complex CH3C(CH2NC)2[CH2NC  -  Cr(CO)5] has been characterized by an X-ray structure analysis allowing a direct comparison of the bonding parameters of coordinated and noncoordinated isocyanide ligands in the same molecule.
    Additional Material: 1 Ill.
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  • 31
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 459-465 
    ISSN: 0009-2940
    Keywords: 1-Aza-4,6-adamantanedione derivatives synthesis ; Radical deoxygenation, nBu3SnH ; Ammonium salts ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Deoxygenation of Substituted 1-Azaadamantane-4,6-diones1-Azaadamantanes 5 and a variety of derivatives are accessible by a triple Mannich reaction of 1,3-cyclohexanediones 1 with hexamethylenetetramine to yield the 1-azaadamantane-4,6-diones 2. Deoxygenation of the sterically hindered and non-enolizable β-dioxo group in 2 succeeds by radical processes. Treatment with NaBH4/MeOH and subsequent chlorination give the dichlorides 4, which are dehalogenated with nBu3SnH. Quaternary ammonium salts 6 are available in high yields.
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  • 32
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 479-484 
    ISSN: 0009-2940
    Keywords: Norcaranes, 7,7-dibromo- ; 1H-Cyclopropa[a]naphthalenes, 1,1-dibromo-1a,2,3,7b-tetrahydro- ; Carbene insertion ; Bicyclo[1.1.0]butane derivatives ; Bicyclo[3.2.0.02,7]heptane derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation of Phenyl-Substituted Derivatives of Tricyclo[4.1.0.02,7]heptane and 1,2,3,4-Tetrahydro-1,2,3-methenonaphthaleneThe phenyl derivatives 3, 4, and 13 of tricyclo[4.1.0.02,7]heptane (1) and 17, 20, and 22 of 1,2,3,4-tetrahydro-1,2,3-methenonaphthalene (2) have been prepared from the dibromocarbene adducts of 1-phenyl-1-cyclohexene, 3-phenyl-1-cyclohexene, 1,3-diphenyl-1-cyclohexene, 1,2-dihydro-2-phenylnaphthalene, 1,2-dihydro-4-phenylnaphthalene, and 1,2-dihydro-2,3-diphenylnaphthalene, respectively, by treatment with methyllithium. The dibromocarbene adduct 10 of 1,6-diphenyl-1-cyclohexene reacts with methyllithium to give the bicyclo[3.2.0.02,7]heptane 11.
    Additional Material: 1 Tab.
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  • 33
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 515-524 
    ISSN: 0009-2940
    Keywords: Dimethylhydrazones, metalated ; Acylation, regioselective ; 1,3-Diketones ; α-Cyano dimethylhydrazones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acyclic and cyclic unsymmetrical ketones 1 are regioselectively acylated via their corresponding metalated dimethyl-hydrazones 3 by using acid chlorides or anhydrides, arylnitriles, ethyl formate, carbon disulfide/methyl iodide, alkyl chloroformates, dialkyl carbonates, phenyl isocyanate, or phenyl isothiocyanate as acylating agents. Subsequent acidic hydrolysis leads to the 1,3-diketones 6 in acceptable to excellent overall yields. The tautomeric structure of the product hydrazones 4, 5, 7, and 8 is determined. Cyanation of 3 with cyanogen bromide affords the α-cyano dimethylhydrazones 9.
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  • 34
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 407-409 
    ISSN: 0009-2940
    Keywords: Arsenic pentafluoride - nitrile adducts ; Cyanogen compounds ; Hard-soft acid-base (HSAB) principle ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Coordination Behaviour of the Nitrogen Bases R - CN (R = H, Cl, I, CH3) and Pyridine towards AsF5 in SolutionThe coordination behaviour of the nitriles R - CN (R = H, Cl, I, CH3) and of pyridine towards the strong Lewis acid AsF5 in solution is investigated and discussed on the basis of the hardsoft acid-base (HSAB) principle. Solution equilibria are studied by means of 1H-NMR spectroscopy. For the equilibrium of HCN, ICN, and AsF5 with the corresponding coordinated Lewis acid - Lewis base adducts the estimated value for the equilibrium constant is in good agreement with the experimental data.
    Additional Material: 3 Tab.
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  • 35
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 417-422 
    ISSN: 0009-2940
    Keywords: Selenocarboxylates, O-triorganosilyl ; Selenone esters ; Seleno-selenol rearrangement ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of O-triorganosilyl selenocarboxylates 2 are prepared by the reaction of sodium or potassium selenocarboxylate 1 with triorganosilyl chlorides. The selenone esters 2 are stable towards heat, but labile towards moisture, and are formed via Se-triorganosilyl selenocarboxylate 3. In the mass spectrometer, isomerization of 2 to its less stable selenol ester 3 takes place, resembling the Schönberg thione-thiol rearrangement.
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  • 36
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 447-452 
    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.
    Additional Material: 2 Ill.
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  • 37
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 453-458 
    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.
    Additional Material: 2 Ill.
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  • 38
    ISSN: 0009-2940
    Keywords: Silanes, acetyl-, Si-functional ; Silanol, acetyl-, crystal structure of ; Microbial reduction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of the Si-Functional Acetylsilanes tBu(Me3SiCH2)[MeC(O)]SiF and tBu(Me3SiCH2)[MeC(O)]SiH as well as Synthesis and Crystal Structure of the Acetylsilanol tBu(Me3SiCH2)[MeC(O)]SiOH: Substrates for Microbial ReductionsThe racemic Si-functional acetylsilanes tBu(Me3SiCH2)[MeC(O)]SiF (1) and tBu(Me3SiCH2)[MeC(O)]SiH (2) and the racemic acetylsilanol tBu(Me3SiCH2)[MeC(O)]SiOH (3) were synthesized from Si(OMe)4 (4) as substrates for microbial reductions [4 → tBuSi(OMe)3 (5) → tBu(Me3SiCH2)Si(OMe)2 (6) → tBu(Me3SiCH2)SiF2 (7) → tBu(Me3SiCH2)[CH2 = C(OMe)]SiF (8) → 1; 8 → tBu(Me3SiCH2)[CH2 = C(OMe)]SiH (9) → 2; 6 → tBu(Me3SiCH2)[CH2 = C(OMe)]SiOMe (10) → 3]. Compounds 1-3 were found to be reduced by cells of Trigonopsis variabilis (DSM 70714) [≡ SiC(O)Me → ≡ SiCH(OH)Me]. The crystal and molecular structure of 3 was studied by singlecrystal X-ray diffraction. In the crystal, racemic 3 forms infinite chains built up by intermolecular O—H…O bonds between the hydroxyl and acetyl groups of molecules of the same absolute configuration.
    Additional Material: 2 Ill.
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  • 39
    ISSN: 0009-2940
    Keywords: Bicyclo[1.1.0]butanes, rearrangement ; Tricyclo[4.1.0.02,7]heptanes, kinetics of thermolysis ; 1,2,3-Methenonaphthalenes, 1,2,3,4-tetrahydro-, kinetics of thermolysis ; Bicyclo[3.2.0]hept-6-ene derivatives ; Benzocycloheptene derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Thermal Rearrangement of the Bicyclo[1.1.0]butane System. A Kinetic Investigation of the Conversion of Tricyclo[4.1.0.02,7]heptanes into Bicyclo[3.2.0]hept-6-enesTricyclo[4.1.0.02,7]heptane (7), its 1- (20) and 2-phenyl derivatives (22), tetracyclo[5.1.0.02,4.03,5]octane (17), 1,2,3,4-tetrahydro-1,2,3-methenonaphthalene (25) as well as its 1- (35), 2- (32), and 3-phenyl derivatives (27) have been thermolyzed in solution in the temperature range between 110 and 230° C. The activation parameters of these reactions have been determined. The parent hydrocarbon 7 is converted into bicyclo[3.2.0]hept-6-ene (11) in high yield, and the other substrates behave analogously, i.e. the cyclobutene derivatives 18, 21, 23, 26, 28, 33, 34, and 36 are formed. Arising from 27, the cyclobutene 28 is observed as intermediate, which is transformed rapidly to a mixture of the benzocycloheptenes 29 and 31. To undergo this ring enlargement, the other cyclobutenes require more severe conditions. The thermal rearrangements of 20, 22, and 27 are accompanied by parallel reactions, which have been identified as acid-catalized processes in the case of 22 and 27 giving rise to the norcarene derivatives 24 and 30, respectively. In 2-phenylmethenonanpthalene 32 two pathways to a cyclobutene derivative exist; they are found to be followed in a 82:18 ratio. The relative reaction rates of all substrates investigated can be interpreted in terms of a consistent mechanistic model. Accordingly, the tricyclo[4.1.0.02,7]heptane system is transformed in a concerted but highly asynchronous process to an (E,Z)-1,3-cycloheptadiene, which then undergoes a rapid conrotatory ring closure to yield the corresponding bicyclo[3.2.0]hept-6-ene.
    Additional Material: 4 Tab.
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  • 40
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 679-689 
    ISSN: 0009-2940
    Keywords: 1,1′-Binaphthyls ; Diphosphanes ; Nickel complexes ; Palladium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 16- and 18-membered diphospha macrocycles (8, 12, and 15) have been synthesized from the corresponding 1,1′-binaphthyl precursors (6, 11, and 14, resp.) and o-phenylenebis(phenylphosphane) by means of high-dilution conditions in 55, 49, and 87% yield. X-ray structure analyses of 8a, 8b, 12b, and 12b · NiCl2 reveal their distinctly different conformations and conformational changes caused by complexation. These structural features are reflected in the pronounced different tendency of the compounds concerned to form Ni(II) and Pd(II) complexes.
    Additional Material: 2 Ill.
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  • 41
    ISSN: 0009-2940
    Keywords: Chalcogeno boron hydride ; Noradamantane structure ; Calculations, SCF ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [(BH2)5S4]-: A New Chalcogeno Boron Hydride Anion with Noradamantane Structure - Theoretical Investigation of the Structure[1]The reaction of NaBH4/THF · BH3 with elemental sulfur produces Na[(BH2)5S4] (4a) with hydrogen evolution. These nucleophilic degradation reactions proceed via [H3B -μ2-S(B2H5)]- (1) and the intermediate 3 by loss of BH4- and cyclization. 4 can also be obtained by addition of 1 to 1,2,4,3,5-trithiadiborolane (5). 4 builds up a noradamantane-like skeleton B5S4. An X-ray structure determination of [(C6H5)4P] · 4 failed because of disordering of the anion. 1H-, 11B-NMR shifts and 1J(11B1H) coupling constants convey further structural information. Structural data have been calculated by SCF methods.
    Additional Material: 4 Ill.
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  • 42
    ISSN: 0009-2940
    Keywords: Trichlorosilylation ; Chlorophosphanes ; Silylphosphanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of Silicon-Silicon Bonds, 2[1]. - Trichlorosilylations of tert-Butyldichlorophosphane and tert-Butylbis(trimethylsilyl)phosphane with Hexachlorodisilane: Synthesis of New Bifunctional (Trichlorosilyl)phosphanesDi-tert-butyl(trimethylsilyl)phosphane (1) and tert-butylbis(trimethylsilyl)phosphane (3) react with one equivalent of hexachlorodisilane with exchange of one trimethylsilyl group by a trichlorosilyl group under mild conditions to give di-tert-butyl(trichlorosilyl)phosphane (2) and tert-butyl(trichlorosilyl)(trimethylsilyl)phosphane (4) in fair yields. tert-Butylbis(trichlorosilyl)phosphane (5) is available from tert-butyldichlorophosphane without organometallic reagents and solvents by simple reductive trichlorosilylation with the help of two equivalents of hexachlorodisilane. 5 is a useful precursor for phosphaalkane synthesis: with pivaloyl chloride, 5 leads to tert-butyl-[tert-butyl(trichlorosilyloxy)methylene]phosphane (6). From 4 with pivaloyl chloride mainly 6 and some known tert-butyl[tert-butyl(trimethylsilyloxy)methylene]phosphane (7) are formed.
    Additional Material: 1 Tab.
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  • 43
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 675-677 
    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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  • 44
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 691-700 
    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.
    Additional Material: 5 Tab.
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  • 45
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 723-728 
    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.
    Additional Material: 3 Ill.
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  • 46
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 739-749 
    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.
    Additional Material: 5 Ill.
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  • 47
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 751-756 
    ISSN: 0009-2940
    Keywords: Transition-metal chemistry ; Hydrogen exchange ; Gas-phase oxidation ; Fourier-transform ion-cyclotrone resonance ; Tandem mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gas-phase experiments on the Fe+-mediated oxidation of 2-propanol and ethanol by 1,3-butadiene are described. The reaction takes place at an atomic Fe+ centre, and labeling experiments uncover its specificity. While the gas-phase reaction of Fe(η4-C4H6)+ with 2-propanol occurs at collision-rate and the analysis of ligand-binding energies, in principle, favour a catalytic cycle for the Fe+-mediated dehydrogenation of 2-propanol by 1,3-butadiene, this conjecture is not born out experimentally due to complicating “side” processes. In addition to the specific interligand two-hydrogen-atom transfer from the alcohol to butadiene, the study of isotopomers reveals several hydrogen-exchange processes preceding dehydrogenation, dehydration, and alkene loss from (C4H6)Fe+ (alcohol) complexes.
    Additional Material: 2 Tab.
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  • 48
    ISSN: 0009-2940
    Keywords: Phosphoranes, bis(methylene), isomerization of ; λ3-Phosphiranes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(methylene)phosphoranes - Synthesis, Spectroscopic Investigations and Thermal Isomerizations to λ3-PhosphiranesA great number of differently substituted bis(methylene)phosphoranes 10 [R - P{ = C(SiMe3)2}2] are obtained by nucleophilic substitution from bis[bis(trimethylsilyl)methylene]-chlorophosphorane (8). The reactions of dichlorophosphanes 1 and methylenephosphanes 3 with lithium carbenoides 2 furnish the mixed derivatives 6 [R - P( = CR1R2)( = CR3R4)] and 7 [R - P( = C(SiMe3)2( = CR3R4)]. Among these the reaction of the sterically less hindered methylenephosphanes 3c, d [R2N - P = C(H)SiMe3, R = Et, iPr] with an excess of the lithium carbenoide 2b results in the formation of the σ4λ5-phosphiranes 11a, b {R2N - P[ = C(H)SiMe3]2}. The sterically highly demanding substituents in 10a - o render great thermal stability, while the mixed bis(methylene)phosphoranes 6, 7 rearrange to the corresponding σ4λ5-phosphiranes 15a-o. Investigations performed between 30 and 180°C reveal that all bis(methylene)phosphoranes, with the exception of 6c, k - m and 7e, can be isomerized. - The phosphino-substituted bis(methylene)phosphoranes 10k, 1 show different reactivity. Light-and thermally induced cleavage of the P - P bond, and dimerization of the corresponding fragments result in the formation of 14 and the diphosphanes 13a, b. The bis(methylene)phosphoranes 10a-o are investigated by UV and NMR spectroscopy.
    Additional Material: 3 Tab.
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  • 49
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 793-800 
    ISSN: 0009-2940
    Keywords: o-Benzoquinone adducts ; Rearrangement reactions ; Elimination reactions ; 1,3,2-Diazaphospholidin-1-ium salts ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: o-Benzoquinone Adducts, Rearrangement and Elimination Reactions of 1,1,3-Trimethyl-1,3,2-diazaphospholidin-1-ium SaltsThe 1,1,3-Trimethyl-1,3,2-diazaphospholidin-1-ium Salts X- [1 (X = [Br, Y = NEt2), 2 (X = [BPh4], Y = Me), 3 (X = [BPh4], Y = Ph), 4 (X = [BPh4], Y = NEt2), 5 (X = [BPh4], Y = tBu)] were treated with o-benzoquinones. The reaction of 1 with tetrachloro-o-benzoquinone furnished the spirophosphorane 6 with an intact N → λ5P donor-acceptor interaction. The reaction of 2, 3, and 4 with 3,5-di-tert-butyl-o-benzoquinone furnished [BPh4]- [8 (Y = Me), 9 (Y = Ph), 10 (Y = NEt2)]. The reaction of 5 with 3,5-di-tert-butyl-o-benzoquinone yielded 7 which exhibited no significant N →λ5P donor-acceptor interaction. The rearrangement product 11 was formed in small amounts during the reaction of 5 with tetrachloro-o-benzoquinone; 11 was also prepared by an alternative route. Thermolysis of the 1,1,3-trimethyl-1,3,2-diazaphospholidin-1-ium salts X- [14 (X = Br), 15 (X = I)] in vacuo led, with elimination of methyl halide, to the 1,3,2-diazaphospholidines 16 (X = Br) and 17 (X = I). The salts were characterized by FAB-MS.
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  • 50
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1079-1081 
    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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  • 51
    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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  • 52
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1111-1118 
    ISSN: 0009-2940
    Keywords: Aldehyde reactions ; Ruthenium clusters ; Oxidative addition ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidative Addition of Aldehydes and Schiff Bases to Ru3(CO)12Aldehydes show a wide variation of their reactive behaviour towards Ru3(CO)12. Aliphatic and simple aromatic aldehydes form simple oxidative addition products Ru3(CO)10(μ-H)(μ-RC = O) (1) either not at all or in low yields as impure compounds, while under forcing conditions dinuclear ruthenium μ-carboxylate complexes or the hydride H2Ru4(CO)13 are formed. Electron-rich aldehydes give good yields of cluster type 1 (R = p-MeOC6H4, p-Me2NC6H4, ferrocenyl). Schiff bases behave similarly, their oxidative addition products being Ru3(CO)10(μ-H)(μ-RC = NR′) (10, R = C6H5, p-MeOC6H4, p-Me2NC6H4, R′ = C6H5, p-MeC6H4). Of the ortho-substituted benzaldehydes, the methoxy compound produces clusters 6 and 7 resulting from aldehyde oxidative addition and aromatic ortho metalation. Salicylaldehyde and its p-tolylimine give the compounds Ru3(CO)8(μ-η2-OC6H4CH = X)2 (9, 11, X = O, NC6H4Me) with a bridging phenolate and a terminally bound aldehydic O or Schiff base NR function. 3-Pyridinecarbaldehyde reacts quickly with Ru3(CO)12 to give products 8 derived from pyridine CH rather than aldehyde CH oxidative addition. The crystal structures of 9 and 11 were determined.
    Additional Material: 2 Ill.
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  • 53
    ISSN: 0009-2940
    Keywords: Iron complexes, dinuclear ; μ-[Cyano(phosphano)alkylidene] ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Replacement of SMe2 at the pseudo-alkylidyne μ-carbon atom of [Fe2Cp2(CO)2(μ-CO){μ-C(CN)SMe2}]SO3CF3 by PR2H (PR2 = PEt2, PCyH, PPhH) results in the formation of the phosphonium salts [Fe2Cp2(CO)2(μ-CO){μ-C(CN)PHR2}]SO3CF3 which upon deprotonation with NEt3 yield the corresponding neutral complexes [Fe2Cp2(CO)2(μ-CO){μ-C(CN)PR2}]. These μ-(phosphanoalkylidene) complexes have been characterized on the basis of IR, 31P{1H}-, 1H-, and 13C{1H}-NMR spectra and by the X-ray molecular structure of [Fe2Cp2(CO)2(μ-CO){μ-C(CN)PEt2}].
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  • 54
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1159-1167 
    ISSN: 0009-2940
    Keywords: Oligolactones, macrocyclic ; Macrocyclization ; Stannylene template ; Template synthesis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dibutylstannylene-mediated macrolactonization of methyl 4,6-O-benzylidene-&7alpha;-D-glucopyranoside (2) with glutaryl and phthaloyl dichloride yields the respective dilactones 6e and 6f and parallel tetralactones 5e and 5f as well as the antiparallel tetralactone 4e in the case of glutarylation. The reaction with malonyl dichloride yields a negligible amount of the parallel tetralactone 5d and that of fumaryl and isophthaloyl dichloride yields polyesters only, a byproduct in all these reactions. The mechanism of stannylene-medidted macrolactonization is discussed incorporating data pertaining to known hexa- and octalactone formation when succinyl dichloride is used. A correlation between stannylene dimer symmetry and tetralactone constitutional isomer selectivity is introduced.
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  • 55
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1191-1203 
    ISSN: 0009-2940
    Keywords: Asymmetric alkylation ; Pyridines, optically active ; Chiral ligands ; Asymmetric synthesis ; Enantioselective catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantioselective alkylation of a variety of aldehydes with diethylzinc was achieved by using catalytic amounts of optically active pyridines and C2-symmetric 2,2′-bipyridines. The products were obtained in good yields with high enantioselectivities. Steric factors of the catalyst structure which govern the stereoselectivity were revealed, and important reaction intermediates were identified by spectroscopic means and singlecrystal X-ray diffraction. The effect of additives on the optical purity of the product was studied. A strong asymmetric amplification was found with catalysts of low ee′s.
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  • 56
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1205-1215 
    ISSN: 0009-2940
    Keywords: Addition, conjugate ; Pyridines, optically active ; Chiral ligands ; Asymmetric synthesis ; Catalysis, enantioselective ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conjugate addition of diethylzinc to enones is catalyzed by a complex derived from Ni(acac)2 and C2-symmetric 2,2′-bipyridine 3 or chiral pyridines 5-12. The products are obtained with optical purities up to 89% ee. A strong positive nonlinear relationship between the enantiomeric excess of the ligand and the ee of the product has been observed. The factors which govern catalyst activity and enantioselectivity have been investigated.
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  • 57
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1235-1241 
    ISSN: 0009-2940
    Keywords: Redox systems ; Electron transfer ; Hetero quinones ; Electron acceptors ; Thieno[3,2-b]thiophene derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multistep Reversible Redox Systems, LVIII[1]. - 2,5-Bis(cyanoimino)-2,5-dihydrothieno[3,2-b]thiophenes - a New Acceptor Type: Synthesis and Common PropertiesThe synthesis of a variety of substituted 2,5-bis(cyanoimino)-2,5-dihydrothieno[3,2-b]thiophenes (4) and the corresponding diones (5) is described. Different substituents on the acceptors 4 and 5 allow the redox potentials of these reversible two-step redox systems to be varied over a wide range.
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  • 58
    ISSN: 0009-2940
    Keywords: Glycidic esters ; Oxiranecarboxylic esters ; Threonine ; allo-Threonine ; Epoxy alcohols ; Flustrates ; Payne rearrangement ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation and Reactions of Ethyl (R,R)- and (S,S)-3-Trifluoromethyloxirane-2-carboxylate, a Versatile, Easily Accessible CF3-Containing Building Block for SynthesisA facile three-step route has been elaborated leading from 4,4,4-trifluoro-3-oxobutanoate to the trifluoro glycidic ester 1 mentioned in the title (0.1-mole scale). Reactions with azide (→ 4, 5) and with organometallic compounds such as cuprates (→ 3, 6), lithium (→ 7, 8), and magnesium derivatives (→ 9-11) furnish novel enantiomerically pure trifluoromethyl-substituted carboxylic esters, ketones, diols, and epoxy alcohols. The latter ones undergo selective isomerizations by Payne rearrangement (11 → 12) in aqueous NaOH/acetone or tert-butyl alcohol.
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  • 59
    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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  • 60
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1297-1300 
    ISSN: 0009-2940
    Keywords: Wagner-Meerwein rearrangement ; Carbocations, tricyclic ; Substitution, nucleophilic ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rearrangements of Tricyclo[3.2.1.12,4]non-6-yl, Tricyclo[4.2.1.12,5]dec-3-yl, and Tricyclo[4.2.2.12,5]undec-3-yl CationsThe tricyclic ketones 5, 9, 13, and 24 were prepared by modified or novel routes. The corresponding tosylhydrazones 10, 11, 14, and 25 were photolyzed in 0.5 N NaOH (NaOD) to generate the title cations 2, 15-17, and 28, respectively, by way of diazonium precursors. The distribution of deuterium labels revealed rapid degenerate Wagner-Meerwein rearrangements of 2 and 28 contrasting the unsymmetrical behavior of the parent bicyclo[3.2.1]oct-6-yl cation (1). The virtually irreversible rearrangement of 17 to 15, on the other hand, mirrors the preferred chair conformation of 1. The results with tricyclic carbocations support our previous explanation for the exceptional reactivity of 1.
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  • 61
    ISSN: 0009-2940
    Keywords: Enantiomerization ; Dynamic complexation gas chromatography ; Homofuran ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By computer simulation of experimental interconversion profiles, obtained by complexation gas chromatography, rate constants of enantiomerization have been determined for homofuran between 95 and 130°C. Since enantiomerization proceeds at similar rates in the mobile and stationary phase, the rate constants obtained by an Arrhenius plot are in excellent agreement with values determined independently by polarimetry between 60 and 90°C. We thus demonstrate that dynamic chromatography can be an easy means for the rapid determination of enantiomerization (or isomerization) barriers of ca. 70-120 kJ mol-1 requiring only minute amounts of racemic sample.
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  • 62
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1313-1318 
    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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  • 63
    ISSN: 0009-2940
    Keywords: Manganese complexes ; Chromium complexes ; Molybdenum complexes ; Tungsten complexes ; Cycloheptatriene ; Cyclooctatriene ; Cyclooctatetraene ; Hydrocarbon-bridged complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrocarbon-Bridged Complexes, XXV[1]. - C-C Coupling of Anionic Tricarbonyl Manganese Complexes of Cyclic Polyenes with Cationic Tropylium Metal Compounds; Preparation and Structure of (OC)3Mn(μ-η5:η6-C7H8-C7H7)M(CO)3, (OC)3Mn(μ-η5:η6-C8H10-C7H7)M(CO)3, and (OC)3Mn(μ-η5:η5-C8H8-C7H7)M(CO)3 (M = Cr, Mo, W)The addition of the anionic complexes [(η4-C7H8)Mn(CO)3]-, [(η4-C8H10)Mn(CO)3]- and [(η4-C8H8)Mn(CO)3]- to the cations [(η7-C7H7)M(CO)3]+ (M = Cr, Mo, W) gives the hydrocarbon-bridged complexes (OC)3Mn(μ-η5:η6-C7H8-C7H7)M(CO)3, (OC)3Mn(μ-η5:η6-C8H10-C7H7)M(CO)3, and (OC)3Mn(μ-η5:η6-C8H8-C7H7)M(CO)3 (M = Cr, Mo, W). The structures of 4b and 6a have been determined by X-ray diffraction.
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  • 64
    ISSN: 0009-2940
    Keywords: Ruthenium(II) complexes ; Ether phosphanes ; Fluxional behavior ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis, Crystal Structure, and Fluxional Behavior of cis-Cl2Ru(CO)(P∽O)(P^O) with cis-Positioned (Ether-Phosphane) LigandsReaction of the ether-phosphane ligands 2a-c with Cl2Ru-(PPh3)3 (1) results in the formation of the bis(chelate) complexes trans-Cl2Ru(P^O)2 (3a-c) (P∽O = η1-P-coordinated; Pb̂O = η2-O,P-coordinated). With CO both Ru-O bonds are cleaved to give all-trans-Cl2Ru(CO)2(P∽O)2 (4a-c). The mono(chelate) complexes 5a-c are obtained from stoichiometric amounts of 3a-c and 4a-c. Upon heating the kinetically controlled products 5a-c are transformed into the thermodynamically more stable isomers cis-Cl2Ru(CO)(P∽O)(P^O) (6a-c). Both 5a-c and 6a-c show fluxional behavior. The higher coalescence temperatures and estimated ΔG≠ values of 6a-c (75, 67, and 70°C, respectively) compared to 5a-c (55, 0, and -10°C, respectively) indicate different exchange mechanisms for 5 and 6. According to an X-ray structure analysis, 6b crystallizes in the monoclinic space group P21/c with Z = 4. The action of CO on 6a-c affords the cis,cis,trans complexes 7a-c.
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  • 65
    ISSN: 0009-2940
    Keywords: Bis(phosphido)-bridged diiron hexa(penta)carbonyl complexes, molecular structures ; Steric strain ; Iron-iron double bond ; Calculations, EHT ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An Unusual Pair of Bis(phosphido)-Bridged Diiron Carbonyl Complexes: [Fe2(CO)n{μ-P(tBu)2}(μ-PCy2)] (n = 5 and 6)Treatment of Na[Fe2(CO)6(μ-CO){μ-P(tBu)2}] with Cy2PCl gives [Fe2(CO)6{μ-P(tBu)2}(μ-PCy2)] (1) which loses CO on heating in toluene to afford [Fe2(CO)5{μ-P(tBu)2}(μ-PCy2)] (2). Complexes 1 and 2 have been characterized spectroscopically and by X-ray analyses. The central Fe2P2 unit in 1 is exactly planar whereas in 2 it is somewhat folded.
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  • 66
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1389-1395 
    ISSN: 0009-2940
    Keywords: 1,3,4-Thiadiazoles ; Ring-chain tautomerism ; Zwitterions ; Lactam thioacylhydrazones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thiohydrazide compounds 1 react with lactam acetals 2 or lactim ethers 3 by condensation giving unusual zwitterionic tautomers 5 of lactam thioacylhydrazones 4. These compounds 5 form mixtures of tautomers in neutral solution. In acidic solution, however, most of them undergo a reversible ringchain transformation to novel 2-(ω-aminoalkyl)-1,3,4-thiadiazole salts 9. Alkylation of zwitterionic thioacylamidrazones 5 gives S-alkylation products 6.
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  • 67
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1405-1407 
    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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  • 68
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1431-1437 
    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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  • 69
    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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  • 70
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1517-1520 
    ISSN: 0009-2940
    Keywords: Interstellar chemistry ; Heterocumulenes ; Charge-reversal mass spectrometry ; Neutralization-reionization mass spectrometry ; Collisional activation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Neutralization-reionization mass spectrometry as well as charge reversal and collisional activation experiments serve to distinguish and assign the connectivities NNCCN and NCNCN to isomeric pairs of anions, neutral radicals and cations of C2N3. Loss of N2 to generate C2N+ is the critical discriminant, and the assignment is further substantiated by subjecting these fragment ions to collisional activation experiments by using tandem-mass spectrometry facilities.
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  • 71
    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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  • 72
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1541-1546 
    ISSN: 0009-2940
    Keywords: 1,3,2,4-Diphosphadigermetanes, 1,3-bis(tert-butylmercurio)- ; Inversion at phosphorus ; 1,3-Diphospha-2,4-digermabicyclo[1.1.0]butanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Structure of New Germanium-Phosphorus Heterocycles Containing a Ge2P2-FrameworkMes(tBu)GeF2 (Mes = 2,4,6-trimethylphenyl) reacts with two equivalents of [LiPH2 · dme] (dme = dimethoxyethane) to give the 1,3,2,4-diphosphadigermetane 1 which was characterized by an X-ray structure analysis. Surprisingly, only the trans-configurated isomer (with regard to the tBu groups at germanium) is formed. In solution at 25°C the latter compound exists as a 1:1 mixture of cis and trans isomers (with regard to the H atoms at phosphorus). Lithiation at phosphorus with tBuLi gives the corresponding 1,3-dilithio derivative which reacts with tBuHgCl to form the 1,3-dimercurio derivative 2. Photolysis of 2 with visible light leads to 3, the first derivative of a 1,3-diphospha-2,4-digermabicyclo[1.1.0]butane with tBu/tBu-exo,exo configuration. As another product of the photolysis the trimercurio compound 5 is isolated and characterized by an X-ray structure analysis.
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  • 73
    ISSN: 0009-2940
    Keywords: Bis(1,2,3-triborolane) ; Isopropylbenzene, tetraborylated ; 1,2-Bis(diisopropylamino)-1,2-diphenylborane-(4) ; 1,1,2,2-Tetrakis(boryl)ethane ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polycyclic Compounds from 2,5-Norbornadiene, Isopropylbenzene, and Dehalogenation Products of Dihalogeno(diorganylamino)boranes. Reaction of Bis(diisopropylamino)phenylborane with Na/K Alloy and Difluoro(diisopropylamino)boraneIn the reaction of 2,5-norbornadiene with Na/K alloy and dichloro(diisopropylamino)borane the species 1 was isolated, which contains six boron atoms in two triborolane rings. From isopropylbenzene and the dehalogenation products of (diisobutylamino)difluoroborane the ethenodiborolodiborol system 2 was isolated. When bis(diisopropylamino)phenylborane is treated with F2BN(i-C3H7)2 and Na/K alloy the diborane(4) derivative 5 and 1,1,2,2-tetrakisborylethane (6) are formed together with bis(diisopropylamino)fluoroborane (7). NMR (1, 11B, 13C, 19F) and MS data are given; for 1, 2, 5, and 6 the X-ray structure analyses were performed.
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  • 74
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1575-1581 
    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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  • 75
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1597-1603 
    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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  • 76
    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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  • 77
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1665-1667 
    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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  • 78
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1687-1695 
    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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  • 79
    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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  • 80
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1773-1775 
    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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  • 81
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1537-1540 
    ISSN: 0009-2940
    Keywords: Selane, bis(sulfinylamido)-, reaction with TeCl4 and TeCl3+ ; Tellurium-nitrogen species ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Routes for the Formation of Te-N Bonds - Synthesis, Structure, and Properties of Cl6Te2N2SBesides Cl2 (1), the reaction of Se(NSO)2 with TeCl4 leads to the formation of [Se2N2S]22+[TeCl5-]2 (2) and the bicyclic heterocycle Cl6Te2N2S (3). The latter is also accessible by treating Se(NSO)2 with TeCl3+AsF6-. Another product of this reaction is the well-known salt [Se2N2S]22+[AsF6-] 2. Treatment of TeCl4 with Me3SiNSO in CH2Cl2 provides 3 on a preparative scale. Its structure has been determined by X-ray crystallography.
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  • 82
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1987-1997 
    ISSN: 0009-2940
    Keywords: Phosphetanium salts ; Phosphoranes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel Syntheses and Reactions of Phosphetanium Salts with a Planar SkeletonCleavage of the P-Si bond of silylphosphanes R2P-SiMe3 (R = iPr, tBu, 2,4,6-Me3C6H2) with excess 1,3-dihalogenpropanes X-[CH2]3-X (X = Br, I) affords phosphetanium salts (3) in good yields. These strained four-membered ring systems are also obtained by alkylation of secondary phosphanes R2PH with X-[CH2]3-X followed by deprotonation of the intermediate phosphonium salts [R2P(H) - [CH2]3-X]+ X- (R e.g. tBu; X = Br, 7b). Silylphosphanes and secondary phosphanes with less bulky substituents preferably form open-chain phosphonium salts with [CH2]3-X or allyl substituents in these reactions. X-ray structural analysis of (3h) reveals planar geometries for the PC3 skeletons of the cations. The reactivity of 3b towards different types of nucleophiles [F-, NH2-, OH-, OR-, Fe(CO)2Cp-, NaN(SiMe3)2, RR′PLi] has been studied. Reaction with CsF or NaNH2, leads to a stable monofluoro or monoamino phosphorane, respectively, with cyclic four-membered PC3 skeletons. In all other cases opening of the phosphetanium ring system occurs leading to derivatives with R2P - [CH2]3 terminal groups. Bidentate and polydentate ligands, e.g. 19-25, with bulky substituents in terminal position have been synthesized in high yields by cleavage of 3b with mono- and bifunctional lithium phosphides. By deprotonation of 3b with MeLi the cyclic ylide 14 is formed. Treatment with acetone or benzaldehyde leads to the unsaturated open-chain phosphane oxides 15a or 15b in a Wittig-type reaction.
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  • 83
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2007-2014 
    ISSN: 0009-2940
    Keywords: Rhodium(I) complexes ; Olefin complexes ; Hydrido(vinyl)rhodium(III) complexes ; C-H Activation ; Carbonyl compounds, α,β-unsaturated, reactions of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies on C-H Activation, VIII[1]. - Hydrido(vinyl)rhodium(III) Complexes from [RhCl(PiPr3)2] and OlefinsThe reaction of [RhCl(PiPr3)2]n (1) with methyl vinyl ketone leads to the formation of the olefin complex trans-[RhCl(CH2 = CHC(O)Me)(PiPr3)2] (2) which rearranges at ambient temperatures to give the hydrido(vinyl)rhodium(III) isomer (3). From 1 and the α,β-unsaturated ketones RCH = CHC(O)Me (R = MeO, Me, Ph) the corresponding hydrido(vinyl) derivatives (5-7) are directly obtained. Treatment of 1 with acroleine CH2 = CHC(O)H gives the olefin complex trans-[RhCl(CH2 = CHC(O)H)(PiPr3)2] (8) that does not react by C-H activation but by elimination of ethylene to form the carbonyl compound trans-[RhCl(CO)(PiPr3)2] (4). The reactions of 1 with CH2 = CHCO2Me, (E)- and (Z)-CH(CO2Me) = CH(CO2Me) afford monomeric (10, 12) or dimeric (14) olefin-rhodium(I) compounds from which 12 is transformed by UV irradiation to give the hydrido(vinyl) isomer (16). Structurally related hydrido(vinyl)rhodium(III) complexes (17) and (PiPr3)2] (20, 21) are obtained either directly from 1 and the α,β-unsaturated carbonyl compound or in two steps via the olefinrhodium(I) precursor. The IR and NMR data of the hydrido(vinyl) compounds prove unambiguously that the vinyl ligand is coordinated by the carbon and the carbonyl oxygen atom.
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  • 84
    ISSN: 0009-2940
    Keywords: Cycloaddition ; Phosphenium ligands ; Phosphinidene(metallo)phosphoranes ; Insertion ; Alkylation ; Tungsten complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cycloaddition Reactions with Phosphenium Metal Complexes, 2. - Cyclized Phosphinidene(metallo)phosphoranes by Addition of “Methylphosphinidene” to Phosphenium and Arsenium Tungsten ComplexesCyclized phosphinidene(metallo)phosphoranes (3a, b, 5) are obtained from Cp(OC)2W = ER2 (E = P, As; R = tBu, oTol) (1a, b, 4) and (MeP)5 (2). Treatment of 3a with CH3I yields the cationic η2-diphosphane complex (6). The reaction of 3b with elemental sulfur and selenium leads to the four-membered metallacycles (X = S, Se) (7a, b).
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  • 85
    ISSN: 0009-2940
    Keywords: Chromium, alkynylcarbene complexes ; Vinylcarbenechromium complexes, β-donor-substituted ; Carbene complexes, vinyl, chelated ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: β-Donor-substituted α,β-unsaturated chromium carbene complexes (CO)5CrC(OEt)C = CR(XR′n) (X = N, O, S; 3, 9, 11-16, 22-25) have been synthesized by Michael addition of amines, alcohols, and thiols to alkynylcarbene complexes (CO)5CrC-(OEt)C≡CR (1). The configurations of the newly formed C-C double bonds have been determined by NOE/NOESY measurements and X-ray crystal structure analysis. These vinylcarbene complexes lose one carbonyl ligand in refluxing tetrahydrofuran to give tetracarbonyl complexes (CO)4CrC(OEt)C = CR(XR′n) (X = N, O, S; 26-28).
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  • 86
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2081-2084 
    ISSN: 0009-2940
    Keywords: Phosphonium ylides ; Wittig reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phosphane Alkylenes, 52[1]. - Reactions of [1-(Trimethylsilyl)alkylidene]triphenylphosphoranes with Carbon Dioxide2-(Triphenylphosphoranylidene) carboxylic acid esters 6 have been synthesized from 1-(trimethylsilylalkylidene)phosphoranes 4 and carbon dioxide. The reactions of the ylides 6 with aldehydes 9 lead to α,β-unsaturated silyl esters 10 in good yields and with high (E) stereoselectivity. Thermolysis of 6d affords (oxovinylidene)triphenylphosphorane (7).
    Additional Material: 2 Tab.
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  • 87
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2111-2117 
    ISSN: 0009-2940
    Keywords: Steric hindrance ; Redox chemistry ; Bicyclopropenyl ; Small rings ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Small Rings, 74[1]. - Hexa-tert-butyl-3,3′-bicyclopropenylTitle compound 3 can be prepared by reductive coupling of tri-tert-butylcyclopropenylium tetrafluoroborate (4a) with lithium. Upon treatment with AgBF4 3 does not undergo valence isomerization to the Dewar form of hexa-tert-butylbenzene (2) but is reoxidized under backformation of substrate 4a. The photochemical behavior of 6 is also unusual: Irradiation at room temperature results in gas evolution. However, instead of 7, the s̰-diketone 5 is isolated. Monoketone 7 is only formed if 6 is irradiated in an organic matrix at -196°C.
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  • 88
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2129-2135 
    ISSN: 0009-2940
    Keywords: Hagihara coupling ; Alkynes ; Anthracenes ; Molecular tweezers ; Nanoscale molecules ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tweezer-Shaped Hydrocarbons1,8-Bis[(arylethynyl)phenyl]- and -[(arylethenyl)phenyl]anthracenes of type I (e.g. 9, 6a) and 1,8-bis{[(arylethynyl)phenyl]-ethynyl}- and -{[(arylethenyl)phenyl]ethynyl}anthracenes of type II (e.g. 16, 13) were synthesized for the first time. Their hydrocarbon framework is formed by Grignard coupling and by Hagihara coupling, respectively. An X-ray analysis of 13 exhibits an approximate planar skeleton, only one aromatic ring showing a considerable deviation from that plane (Figure 2). The UV and fluorescence properties are discussed. In spite of their preorganized and rather rigid tweezer-shape the new hydrocarbons do not seem to use their multiple bonds for the cooperative binding of transition metal cations.
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  • 89
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2155-2157 
    ISSN: 0009-2940
    Keywords: Photocycloaddition, intermolecular [2 + 2] ; Paddlanes ; Cyclophane, [23](1,3,5)- ; Cyclobutane ring ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The symmetrical and unsymmetrical title compounds 3 and 4 were prepared by intermolecular photocycloaddition of 1,3,5-trivinylbenzene in 1% yield. The ratio of symmetrical and unsymmetrical paddlanes was 24:76, i.e. nearly a statistical one.
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  • 90
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2165-2170 
    ISSN: 0009-2940
    Keywords: Niobium telluride iodide ; Tantalum telluride iodide ; One-dimensional chain compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: NbTe4I and TaTe4I, Two New Telluride Iodides with Chain StructureNbTe4I and TaTe4I, are synthesized in almost quantitative yields by reaction of the elements in the appropriate ratio at 540°C and 480°C, respectively. The crystal structure determinations show that both structures are built up from quasi one-dimensional Nb(Te2)2 and Ta(Te2)2 chains that are separated by isolated iodine atoms. The metal-metal distances within these chains are outside the metal-metal bonding range. Both compounds are formally described as (Nb5+)(Te22-)2(I-) and (Ta5+)(Te2-2)2(I-), and semiconducting properties must be assumed. Short Te-I contacts between Te atoms of and I atoms between the chains indicate significant anion-cation charge transfer.
    Additional Material: 4 Ill.
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  • 91
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2187-2197 
    ISSN: 0009-2940
    Keywords: (9-Anthracenyl)phosphanes ; photo-dimerization of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of the (9-anthracenyl)phosphanes 2 to 7 and of the metal carbonyl complexes 8 and 9 are described. Both 1 and 4 undergo [4 + 4] cycloaddition when irradiated, forming the dimers 10 and 11. Only one of the six possible rotamers for 10 is formed. For 11 one additional rotational isomer is observed. The relationship between the [4 + 4] dimerization and steric effects of the PR2 group is discussed. The compounds 6, 8 and 11 were characterized by X-ray diffraction. The structure of 6 was rendered imprecise by the presence of disordered toluene, but the influence of the bulky anthracenyl groups was clear, with wide C—P—C angles of 110.4°. The molecule displays imposed threefold symmetry. The two independent molecules of complex 8, which crystallizes as a dichloromethane hemisolvate, are closely similar to each other; the W—P bond lengths are 254.3 and 253.4 pm. The W—C bonds trans to phosphorus are 4 pm shorter than those cis. The phosphane dimer 11 crystallizes with imposed centrosymmetry. The H atom positions, which could be tentatively identified from difference syntheses, indicate a different rotamer than was formed for the analogous fluorophosphane dimer 10.
    Additional Material: 6 Ill.
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  • 92
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2225-2232 
    ISSN: 0009-2940
    Keywords: 1,6-Methano[10]annulenes, 3,4-disubstituted ; Cycloheptatriene-1,6-dicarbaldehyde, monoolefination of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactive 3,4-Disubstituted Derivatives of 1,6-Methano[10]annulene and their Synthetic PossibilitiesEthyl 4-bromo-1,6-methano[10]annulene-3-carboxylate (4) is synthesized in three steps from cycloheptatriene-1,6-dicarbaldehyde 1. The key step of this conversion is a highly selective monoolefination of 1. The synthetic possibilities of 4 are discussed.
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  • 93
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 2239-2242 
    ISSN: 0009-2940
    Keywords: [3](1,8)Biphenylenophane ; Conformational mobility ; Deformed molecules ; Strained molecules ; TosMIC cyclization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Extremely Deformed (Biphenylene)Hydrocarbon SkeletonsThe tetracyclic carbon skeleton 2-oxo[3](1,8)biphenylenophane (4) was synthesized by cyclization of a mixture of the bis(bromomethyl) compounds 7a, b with p-tolylsulfonylmethyl isocyanide. 2-Hydroxy[3](1,8)biphenylenophane (5) and the [3](1,8)biphenylenophane hydrocarbon 6 were obtained by reduction of 4 with LiAlH4 and NaBH4, respectively. X-ray analyses of 4 and 6 illustrate the dramatic deformation of bond lengths and angles in these molecules.
    Additional Material: 1 Ill.
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  • 94
    ISSN: 0009-2940
    Keywords: Azabutadienes ; Isoxazoles ; Tetrahydropyridines ; Diels-Alder reactions ; Sequential transformations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Condensation of aldehydes 1a-e with 5-amino-3-methylisoxazole (4) gives the corresponding imines 5a-e with a 2-aza-1,3-butadiene moiety, which cyclize selctively, e.g. 5a to form the trans-fused tetrahydropyridine 7a and 5c to yield the cis-fused cycloadduct 8c. The astounding difference in the selectivity of these reactions is explained by electronic effects and suggests a change in the dominating interactions of the orbitals in the transition structure. The structure of 7a is elucidated by an X-ray analysis.
    Additional Material: 1 Ill.
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  • 95
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1829-1834 
    ISSN: 0009-2940
    Keywords: Hydrogen bis-L-pyroglutamates, lithium, sodium, potassium ; Pyroglutamate coordination and conformation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lithium, sodium and potassium hydrogen bis-L-pyroglutamate [Li(L-pGlu)(L-pGluH)], [Na(L-pGlu)(L-pGluH)] and [K(L-pGlu)(L-pGluH)], respectively, have been prepared by reaction of aqueous solutions of the metal hydroxides with L-pyroglutamic acid in the molar ratio 1:2, or in methanol. Crystalline samples of the salts could be obtained by slow evaporation of solutions of the salts in methanol. In the solid state, Li(L-pGlu)(L-pGluH) adopts a chain structure with the lithium atoms arranged in double strands. Adjacent metal centers are bridged by the carboxylate groups of the L-pGlu- ligands. The L-pGluH ligands are attached to the metal centers through the amide oxygen atoms. Na(L-pGlu)(L-pGluH) forms a three-dimensional coordination polymer with two half-occupied sodium positions, one L-pGlu- and one L-pGluH ligand in the asymmetric unit. The carboxyl and carboxylate groups of the L-pGluH and the L-pGlu- ligands are bridging the sodium centers, giving rise to eight-membered rings, which consist of two sodium atoms, a carboxyl and a carboxylate group. The hydrogen atoms of the carboxyl group of the L-pGluH ligands are involved in strong hydrogen bonds between a carboxyl and an adjacent carboxylate oxygen atom. K(L-pGlu)(L-pGluH) adopts a layer structure with strands of potassium atoms. The metal centers are connected through bridging carboxyl and carboxylate groups of the L-pGluH and L-pGlu- ligands, respectively. The structure features eight-membered ring units comparable to those observed for Na(L-pGlu)(L-pGluH), again with the hydrogen atom of the carboxyl group engaged in a strong transannular hydrogen bond. The amide oxygen atoms of the L-pGlu- and the L-pGluH ligands are coordinated to the metal centers of adjacent coordination chains. The results of 1H- and 13C—NMR investigations of aqueous solutions of the compounds indicate extensive electrolytic dissociation in dilute solutions.
    Additional Material: 6 Ill.
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  • 96
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1843-1849 
    ISSN: 0009-2940
    Keywords: Dehydrogenation, with Hg-EDTA complex ; Amide oximes ; Nitrones ; Quinazoline 3-oxides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amide Oxime Functions as Neighbouring Groups in Cyclodehydrogenation ReactionsDehydrogenation of the o-(tertiary amino)benzamide oximes 4, which are monosubstituted at the amide N atom of the neighbouring group, by the mercury edta complex yields tricyclic amino nitrones 9 with a quinazoline 3-oxide moiety or lactams 8. Product formation depends on the nature of the N substituent, the size of the amine ring, and the reaction conditions. The configuration of the amide oximes and the conformation of the tricyclic systems is determined by NMR-spectroscopic methods.
    Additional Material: 4 Tab.
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  • 97
    ISSN: 0009-2940
    Keywords: Carbene complexes, cycloaddition reactions of ; Carbene complexes, reactions with alkynes ; Benzocyclo-heptatrienes ; 2-Oxybenzoanellation ; (Cycloheptatrienylmethyl)carbene complexes of chromium and tungsten ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organic Syntheses via Transition Metal Complexes, 60. - Novel Type of Benzoanellation with Carbene Complexes and Alkynes. - 2-Oxybenzoanellation of Cycloheptatriene via (Cycloheptatrienylmethyl)carbene Complexes of Chromium and TungstenWe report on a three-step procedure for the regiospecific 2-oxybenzoanellation to cycloheptatriene by means of Fischer carbene complexes and alkynes. The first step involves the formation of (cycloheptatrienylmethyl)carbene complexes LnM=C(OEt)—CH2-c-C7H7 [1, LnM = Cr(CO)5 (a), W(CO)5 (b)] from the corresponding methylcarbene complexes and a tropylium salt. 1 reacts with the alkyne Et2N—C≡C—Me (2) to give the (E)- and (Z)-1-amino(1-alkenyl)carbene complexes LnM=C(NEt2)—C(Me)=C(OEt)—CH2—c-C7H7 (3 and 4 resp.). Thermolysis of 3b [LnM = W(CO)5, 100°C, 5 h] finally leads to elimination of W(CO)5(Et2NH) (6b) and the regiospecific formation of the ethoxybenzocycloheptatrienes 5,7, and 8 in 92% total yield. The reaction is kinetically controlled and yields an isomeric ratio of 5:7:8 = 60:12:20% with the thermodynamically less stable isomer 5 predominating.
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  • 98
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1889-1894 
    ISSN: 0009-2940
    Keywords: Fluorosulfines ; Fluorothione S-oxides ; Diels-Alder adducts ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Fluorosulfines XF2C(F)C = SO (X = F, Cl, Br), Their Synthesis and Unusual Type of DecompositionA new route for the synthesis of the sulfenyl chloride 3 opens an easy access to fluoro(trifluoromethyl)sulfine (6) by hydrolysis of 3, trapping 6 by Diels-Alder reaction with anthracene, and thermolysis of the formed compound 8. By addition of the thioacetyl fluorides XF2C(F)C = S (X = Cl, Br) to anthracene compounds 9a, b are obtained, which could be oxidized to the sulfene adducts 12a, b as well as to the sulfine adducts 13a, b. Thermolysis of the latter yields the sulfines 17a, b, which are unstable at room temperature. A second approach to 17a involves oxidation of 1,3-dithietane 11a to its S-oxide 14a (e.g. via an S,S-difluoro compound 15a) and subsequent thermolysis, but thermal decomposition predominates. An unusual decomposition has been observed for 17a, b which was hitherto unknown for sulfines.
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  • 99
    ISSN: 0009-2940
    Keywords: 1,3,4-Oxadiazine-2-carboxylate, methyl 6-oxo-5-phenyl- ; Diels-Alder reactions ; Ketenes, γ-oxo- ; δ-Lactones, δ-chloro- ; β-Lactones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cycloadditions of 6H-1,3,4-Oxadiazin-6-ones (4,5-Diaza-α-pyrones), 11. - δ-Chloro δ-Lactones from γ-Oxo KetenesPrepared from 1,3,4-oxadiazinone 1 with norbornene, cyclopentene, cyclopentadiene, and indene, the γ-oxo ketenes 2, 5, 6, and 7 have been converted into the δ-chloro δ-lactones 3, 8, 9, and 10, respectively, by treatment with hydrogen chloride. The configuration of 10 has been determined by an X-ray structural analysis. These pseudo chlorides prove to be stable against methanol. Only in the presence of sulfuric acid as catalyst 3 suffers methanolysis to yield diester 4. On thermolysis, the γ-oxo ketenes are transformed into β-lactones. In particular, 6 and 7 gave 13 and 12, respectively. Formed also on photolysis of 6, β-lactone 13 partly isomerized to β-lactone 14 on prolonged heating.
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  • 100
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    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1953-1956 
    ISSN: 0009-2940
    Keywords: Zirconium-aluminium dimetallic complexes ; Carbon, planar-tetracoordinate ; μ-Alkyne complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Simple Synthesis of Dimetallic Zirconium/Aluminium Compounds Containing Planar-Tetracoordinate Carbon(η2-Alkyne)(trimethylphosphane)zirconium complexes [alkyne = cyclohexyne (3a) or diphenylacetylene (3b)] react with diisobutylaluminium hydride at room temperature by PMe3 cleavage and addition of H—Al(isobutyl)2 to the in situ-generated (η2-alkyne)ZrCp2 intermediate to give the dimetallic Zr,Al compounds 4. These thermodynamically stable complexes contain a planar-tetracoordinate carbon center whose uncommon coordination geometry is stabilized by a combination of the s̰-donor interaction with both electropositive metals and the π-conjugation of the Zr—C = C moiety.
    Additional Material: 2 Ill.
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