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  • 1
    Electronic Resource
    Electronic Resource
    Replacement of One CO Unit in Dicarbonyl(η5-cyclopentadienyl)cobalt Derivatives by Bis(tert-butylsulfonyl)acetylene (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 629-632 
    Details
    ISSN: 1434-1948
    Keywords: Alkyne complexes ; Carbonyl complexes ; Cobalt ; CO replacement ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of dicarbonyl(η5-cyclopentadienyl)cobalt (1) and some of the Cp-ring substituted congeners with bis(tert-butylsulfonyl)acetylene (BTSA) results in the replacement of one CO group by the BTSA moiety. The variation of the yields and reaction times indicates a dependence of the reactivity of 1-6 with BTSA as a function of substituents. X-ray investigations of the products show that the alkyne unit is strongly bound to the metal.
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  • 2
    Electronic Resource
    Electronic Resource
    Novel Chiral Oxazoline Ligands for Potential Charge-Transfer Effects in the Rh(I)-Catalysed Enantioselective Hydrosilylation (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 771-781 
    Details
    ISSN: 1434-1948
    Keywords: Oxazolines ; Charge-transfer ; 4,4′-Bipyridine ; Enantioselective hydrosilylation ; Rh(I)-complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel 2-(4,4′-bipyridin-2-yl)oxazolines, bearing a chiral oxazoline moiety, were synthesised starting from 4,4′-bipyridine and selectively monomethylated in the N′-position. After coordination to rhodium these electron-poor ligands are supposed to exhibit charge-transfer effects with electron-donating substrates in the Rh(I)-catalysed enantioselective hydrosilylation (see next publication). Similar effects were expected from 4,4′-bipyridine- and pyrazine-bisoxazolines after complexation with rhodium. For comparison 2-(4-phenylpyridin-2-yl)oxazoline ligands were synthesised. Rh(I)-complexes of selected ligands were prepared and characterised, including an X-ray structure analysis.
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  • 3
    Electronic Resource
    Electronic Resource
    Reactions of 1,8-Diheterocyclotetradeca-4,11-diynes with (η4-Cycloocta-1,5-diene)(η5-cyclopentadienyl)cobalt (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 499-504 
    Details
    ISSN: 1434-1948
    Keywords: Alkynes ; Heterocycles ; Cyclizations ; Cobalt ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The following monocyclic and bicyclic 14-membered diynes were treated with [CpCo(cod)]: 1-oxacyclotetradeca-4,11-diyne (2), 1,8-dioxacyclotetradeca-4,11-diyne (3), cyclotetradeca-4,11-diynone (4), cyclotetradeca-4,11-diyne-1,8-dione (5), 1,1,8,8-tetramethyl-1,8-disilacyclotetradeca-4,11-diyne (6), 1-allyl-1-azacyclotetradeca-4,11diyne (7), 1,8-dipropyl-1,8-diazacyclotetradeca-1,11-diyne (8), 1,8-diallyl-1,8-diazacyclotetradeca-4,11-diyne (9), 1,8-diazabicyclo[6.6.4]octadeca-4,11-diyne (10), 1,8-diazabicyclo[6.6.6]eicosa-4,11-diyne (11), 1,10-diazabicyclo[8.6.6]docosa-13,19-diyne (12) and 1,12-diazabicyclo[10.6.6]tetracosa-15,21-diyne (13). In all cases we obtained an intramolecular cyclobutadiene complex stabilized with a CpCo fragment (15-26). For 3 we could isolate, besides the cyclobutadiene complex 16, the trimerization product 28. In the cases of 15, 16, 18, 20, 23, 25, and 26 the structure of the cylobutadiene complexes could be confirmed by X-ray studies. Common to all structures is a boat-like conformation of the tricyclic unit containing the cyclobutadiene ring. The two cycloheptene units adopt a chair conformation in which the heteroatom is removed from the metal center.
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Preparation and Properties of Stelladiones (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 171-176 
    Details
    ISSN: 1434-193X
    Keywords: Stelladiones ; Photoelectron spectroscopy ; Calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tricyclo[3.3.0.03,7]octane-2,4-dione (2,4-stelladione, 3), tricyclo[3.3.0.03,7]octane-2,6-dione (2,6-stelladione, 4), and 2-oxotricyclo[3.3.0.03,7]octane-6-thione (5) were synthesized. Key steps in the procedures were a Paterno-Büchi reaction followed by an oxetane splitting with a strong base. Structure analysis on single crystals of 4 and 5 revealed long central C-C bonds (1.59 Å) of the stellane skeleton. The He(I) photoelectron spectra of 3, 5, and 4-methylenetricyclo-[3.3.0.03,7]octan-2-one (9) were recorded and interpreted on the basis of quantum-mechanical calculations (HF-SCF, 6-31G* basis). The large energy difference between the first PE bands of 3 (0.8 eV) is due to a strong interaction between the lone pairs on the oxygen atoms and the σ frame.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and Properties of 7,7,12,12-Tetramethyl-1,4-dioxacyclotetradecane-8,9,10,11-tetrone (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1303-1310 
    Details
    ISSN: 1434-193X
    Keywords: Ketones ; Alkynes ; Cyclic voltammetry ; Photoelectron spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The fourteen-membered ring of 7,7,12,12-tetramethyl-1,4-dioxacyclotetradecane-8,9,10,11-tetrone (4) was built up from 1,2-bis(2′-chloroethoxy)ethane, two units derived from isobutyric acid and acetylene. Key intermediates were 2,2,11,11-tetramethyl-5,8-dioxadodecane-1,12-diol (8), 7,7,12,12-tetramethyl-1,4-dioxa-9-cyclotetradecyne-2,8-diolprotected by one tetrahydropyran group (15), and 8,11-dihydroxy-7,7,12,12-tetramethyl-1,4-dioxacyclotetradecane-9,10-dione (18). X-ray investigation on single crystals of the (R,S) isomer 18a revealed a transannular interaction between the dioxaethane bridge and the dicarbonyl moiety. Calculations (HF/6-31G*) on 4 predict relatively short distances between the oxygen atoms of the dioxyethane bridge and the (CO)4 part. Investigations by means of cyclic voltammetry, PE and UV/Vis spectroscopy on 4 reveal an interaction between the dioxaethane bridge and the (CO)4 group.
    Additional Material: 4 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Increasing Enantioselectivities and Reactivities by Stereochemical Tuning: Fenchone-Based Catalysts in Dialkylzinc Additions to Benzaldehyde (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1785-1792 
    Details
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Zinc ; Transition structures ; QM/MM computations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Trimethylsilyl substitutions of the fenchyl alcohols [(1R,2R,4S)-exo-(2-Ar)-1,3,3-trimethylbicyclo[2.2.1]heptan-2-ol, Ar = 2-methoxyphenyl (1) and Ar = 2-(dimethylaminomethyl)phenyl (2)] yield the chiral ligands 3 [Ar = 2-methoxy-3-(trimethylsilyl)phenyl] and 4 [Ar = 2-(dimethylaminomethyl)3-(trimethylsilyl)phenyl]. Increased reactivities and enantioselectivities in diethylzinc additions to benzaldehyde are obtained from 3 (63% ee R) and 4 (93% ee S), relative to 1 (26% ee S) and 2 (73% ee S). X-ray crystal structures of 3 and of its methylzinc complex 3-Zn reveal out-of-plane bending of the methoxy groups as major geometrical consequences of the trimethylsilyl substitutions. Analyses of QM/MM ONIOM μ-O transition-structure models for 1, 2, 3, and 4 show that trimethylsilyl-induced distortions of methoxy and of dimethylaminomethyl groups explain the observed increased enantioselectivities.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Syntheses and Properties of S2-Bridged Benzidines (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2409-2416 
    Details
    ISSN: 1434-193X
    Keywords: Sulfur heterocycles ; Rearrangements ; Reductions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of 1,2-benzodithiino[5,4,3-cde][1,2]benzodithiin-2,7-diamine (1) and dithio-bridged benzidine 2 have been achieved. The starting material for the synthesis of 1 was 1,3-diiodo-5-nitrobenzene (15) which was transformed by conventional means into 1,2-bis[3,5-bis(ethylthio)phenyl]diazane (19). The benzidine rearrangement of 19 in the presence of HBF4 at -30 °C yielded 4,4′-diamino-2,2′,6,6′-tetraethylthiobiphenyl (20) in 50 % yield. Treatment of 20 with sodium in ammonia and work-up in the presence of air yielded 1. The latter compound could be reduced with LiAlH4 to the tetrathiol 20a. The starting material for the preparation of 2 was 3-chloro-1-iodo-5-nitrobenzene (23), a side product of the preparation of 15. It was transformed analogously to the preparation of 1 into 1,2-bis(3-ethylthiophenyl)diazane (28). The benzidine rearrangement of 28 in presence of HBF4 at -30 °C afforded 4,4′-diamino-2,2′-bis(ethylthio)biphenyl (29) in 49 % yield. Treatment of 29 with sodium in ammonia and work-up under aerobic conditions yielded 2. Quantitative reduction of 2 to the thiol 29a could be achieved with LiAlH4. The reversible electrochemical reduction of 1 on unmodified glassy carbon electrodes leads to a product to which the structure of 3 was assigned.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Komplexe von Metallen der dritten Hauptgruppe mit [(en)2MIII(OH)2]-Liganden (M = Cr, Co) (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 797-804 
    Details
    ISSN: 0009-2940
    Keywords: Heteronuclear complexes ; Ligand [(en)2MIII(OH)2]+ (M = Cr, Co) ; Complexes of third group elements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexes of Third Group Elements with [(en)2MIII(OH)2] Ligands (M = Cr, Co)Heteronuclear complexes are formed on reaction of cis-[(en)2-MIII(OH)(H2O)]2+ (M = Cr, Co; en = ethylenediamine) with A1III, GaIII, InIII, and T1III in aqueous solution. The following salts with tetranuclear cations have been isolated: [A1{(OH)2-Cr(en)2}3](S2O6)3 · 13 H2O (1), [A1{(OH)2Co(en)2}3](S2O6)3 · 5 H2O (2), [Ga{(OH)2Co(en)2}3](S2O6)3 · 5 H2O (3), [In{(OH)2-Cr(en)2}3](S2O6)3 · 6 H2O (5), and [In{(OH)2Co(en)2}3]-(ClO4)4Cl2 · 4 H2O (6). Furthermore, the dinuclear neutral complexes [InCl4{(OH)2Cr(en)2}] (4) and [TlCl4{(OH)2-Cr(en)2}] · 0.5 H2O (7) are prepared. X-ray analyses confirm that in all cases the [(en)2MIII(OH)2] groups act as bidentate ligands in the hydroxo-bridged heterometallic complexes.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270502
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  • 9
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    Gold Phenolate Complexes: Synthesis, Structure, and Reactivity (2013)
    American Chemical Society
    Details
    Publication Date: 2013-04-19
    Print ISSN: 0276-7333
    Electronic ISSN: 1520-6041
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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  • 10
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    Synthesis and Evaluation of 5-Phenyl-1H-1,4-benzodiazepin-2(3H)-one-Based Palladium Complexes as Precatalysts in C−C Bond Forming Reactions (2005)
    American Chemical Society
    Details
    Publication Date: 2005-11-01
    Print ISSN: 0276-7333
    Electronic ISSN: 1520-6041
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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