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  • 1
    Electronic Resource
    Electronic Resource
    Catalytic and Structural Features of Hydroxy and Methoxy Groups as Hemilabile Coordinating Ligands in Chiral (Diphosphane)rhodium(I) Hydrogenation Catalysts (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1291-1295 
    Details
    ISSN: 1434-1948
    Keywords: Asymmetric catalysis ; Hydrogenations ; Hemilabile ligand ; Hydroxy phosphane ; Methoxy phosphane ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of two threo-arranged methoxy or hydroxy groups as hemilabile ligands in seven-membered (diphosphane)RhI chelates upon the asymmetric hydrogenation is studied. In comparison to the parent complex based on 1,4-bis(diphenylphosphanyl)butane (DPPB) a lowering of the reaction rate is caused by the hemilabile ligands. The catalyst bearing the hydroxy groups gives significantly higher enantioselectivities than the corresponding methoxy complex (by ca. 35 % ee). X-ray structural analysis reveals that the oxygen atom of the hydroxy group is by 0.9 Å closer to the metal center than that of the methyl ether. 31P-NMR studies give evidence that the dihydroxy diphosphane ligand binds at low temperature exclusively in the η3-coordination mode, whereas for the dimethoxy complex also an η2-coordinated isomer can be found. These differences in complexation could be responsible for the superior enantioselectivities achieved with this and other hydroxy catalysts.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Nachweis chiraler Dihydrido-Katalysator-Substrat-Komplexe während der Hydrierung von Itaconsäuredimethylester mit Bisphosphinit-Rhodium(I)-KatalysatorenDiese Arbeit wurde von der Volkswagenstiftung, dem Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF), der Deutschen Forschungsgemeinschaft (SFB 334: Wechselwirkungen in Molekülen) und dem Fonds der Chemischen Industrie unterstützt. (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 109 (1997), S. 1155-1156 
    Details
    ISSN: 0044-8249
    Keywords: Heterogene Katalyse ; Hydridokomplexe ; NMR-Spektroskopie ; Parawasserstoff ; Rhodium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19971091025
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  • 3
    Electronic Resource
    Electronic Resource
    Sterically stressed amino- and PH-functional di-t-butyl-o-phosphinophenols - Intramolecular interaction and formation of benzoxadiphospholes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 9 (1998), S. 183-193 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lithium and sodium o-lithio-4,6-di-t-butyl-phenolates 1 and 2 react, successively, with ClP(NMe2)2 and ClSiMe3 to give 2-(Me2N)2P-4,6-t-Bu2C6H2OSiMe3 3. 1 and ClP(NMe2)Ph furnish a small amount of the analogous compound 4 but mainly diastereoisomers of a C, O-diphosphinylation product 5A/B, which exhibit large through-space coupling constants (4JPP = 152 and 237.5 Hz). Under certain conditions, the P-N bond is attacked, and triphosphines 6 and 7 are formed. Alcoholysis of 3-5 and subsequent reduction with LiAlH4 yields the respective bulky primary and secondary phosphinophenols 8 and 9. Both decompose partially on distillation, affording tBu2C6H3OH and the cyclic diphosphines 10 and 11. 10, a further dihydro-benzoxadiphosphol 13 and a phosphinidene-phosphorane 14 are formed by reaction of 8 with P(NMe2)3. The molecular structure of bicyclic 10, folded at the P-P bond, is reported. The uncommon features - unselective disubstitution of 1, P…P interactions in 5 and 6, facile P-C cleavage of 8 and 9, and diphosphine formation - reveal a dramatic influence of the bulky substituents in the 6-position on the chemistry of 2-phosphinophenols. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:183-193, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    P/O ligand systems: Synthesis and reactivity of primary and secondary o-phosphinophenols (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 8 (1997), S. 383-396 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several organometallic reagents such as lithium 2-lithio 4-methylphenolate 1 intermediates formed by orthometallation of o-bromoaryloxy-phosphorus(V)- 2 or -phosphorus(III)-derivatives 3 with magnesium and sodium, respectively, as well as O-methoxymethyl-protected o-lithio-4-methylphenol 4 were used to synthesize suitable precursors 5,6,9,10 of primary and secondary o-phosphinophenols. The P-C bond formation involved coupling with ClPR(NMe2), CIPR(O)(OEt) or an intramolecular carbanionic O → C shift of the P-substituent. Reduction with LiAlH4, in the cases of phosphonous or phosphinous acid amides after alcoholysis (to 7,8,11), produced primary and secondary o-phosphinophenols 12, respectively, or O-protected derivatives 13. o-Phosphinophenols 12 are easily protonated at the phosphorus atom, supported by a P+-H … O hydrogen bridge. Metallation (14), acylation, and silylation (16,17) take place preferably at the hyxdroxy group and alkylation at the phosphorus atom. Alkylation of 12 and 14 was found to be slow, but C,O-dilithiated species 15 react to give P-secondary (12b,d,e,) or P-tertiary products (20,21). Cyclization of 15a with Me2SiCl2 affords the 2,3-dihydro-1,3,2-benzoxaphosphasilol 22, cyclocondensation of 12c with RP(NMe2)2 or ClP(NMe2)2 furnishes 2,3-dihydro-1,2,3- benzodiphospholes 23 and 24. A phosphiniden-phosphoran 25 is detected in the reaction between 12a and P(NMe2)3. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8: 383-396, 1997
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    P/O Ligand Systems: Synthesis, Reactivity, and Structure of Tertiary o-Phosphanylphenol Derivatives (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 431-431 
    Details
    ISSN: 0009-2940
    Keywords: o-Phosphanylphenols ; P,O hybrid ligands ; P asymmetry ; C,O-dilithium reagents ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300320
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  • 6
    Electronic Resource
    Electronic Resource
    P/O Ligand Systems: Facile Synthesis, Structure, and Catalytic Tests of 2′-Phosphanyl-1,1′ -phenyl-2-ols and 2′-Phosphanyl-1,1′-binaphthyl-2-ols (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1663-1670 
    Details
    ISSN: 0009-2940
    Keywords: Lithiation ; P ligands ; NMR spectroscopy ; Molecular structure ; Hydrogenations ; Hydroformylations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A facile synthesis of 2′-phosphanyl-1,1′-biphenyl- and 2′-phosphanyl-1,1′ -binaphthyl-2-ols and their silyl ethers has been developed, consisting of electron-transfer-catalyzed ring-opening of dibenzofuran and dinaphthofuran, respectively, subsequent reaction with chlorophosphanes, and work-up with acetic acid or ClSiMe3. Studies of the molecular and crystal structures reveals the presence of P - H - O bridging bonds in the more basic tBuPhP derivative and a nearly perpendicular arrangement of the aryl planes in the biphenyl derivatives. The barrier to rotation of the aryl planes about the C-C axis was determined by NMR in the case of the P-asymmetric derivative 3d, using the appearence of diastereoisomers by atropisomerism and P-asymmetry. Comparative screening tests of the title compounds, phosphanyl phenols and phosphanylnaphthols in homogeneous Rh-catalyzed reactions demonstrate catalytic activity in hydroformylation reactions and superior properties of the biphenyl- and binaphthyl-2-ol derivatives in relation to other P-O ligands.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301118
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  • 7
    Electronic Resource
    Electronic Resource
    Syntheses, Structures, and Reactivity of 1-Phosphanylnaphth-2-ols (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1061-1071 
    Details
    ISSN: 0009-2940
    Keywords: Phosphanylnaphthol ; PO ligands ; Chelate complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: P-tertiary or amino-substituted 1-phosphanylnaphth-2-yl silyl ethers 3 are synthesized by stepwise reaction of lithium 1-lithio-2-naphtholate 1 with chlorophosphanes and ClSiMe3. The free phosphanylnaphthols 4 are prepared by alcoholysis. As established by characteristic coupling constants and X-ray structural analyses (of 3c, 4c), 3 exhibit in solution and in the solid state a cis-bisecting conformation, whereas 4 prefers the opposite trans-bisecting arrangement, allowing easy protonation and formation of chelate complexes. Substitution reactions of phosphanylnaphtholates 2 with Ph2PCl and formation of chelate complexes LNi-η5-Cp and L2Pd are described. Attempts to prepare secondary and primary phosphanylnaphthols failed because of facile cleavage of the P-C(naphthyl) bond in PH-substituted 1-phosphanylnaphth-2-ols.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961290914
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  • 8
    Electronic Resource
    Electronic Resource
    P/O Ligand Systems: Synthesis, Reactivity, and Structure of Tertiary o-Phosphanylphenol Derivatives (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1547-1560 
    Details
    ISSN: 0009-2940
    Keywords: o-Phosphanylphenols ; P,O hybrid ligands ; P asymmetry ; C,O-dilithium reagents ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of C,O-dilithium reagents 1 (M = M′ = Li) or C,O-lithium-sodium reagents 1 (M = Li, M′ = Na) with chlorophosphanes afford C,O-disubstitution products 2 or phosphanylphenolates 3 which are treated subsequently with ClSiMe3 to give 4-methyl- and bulky 4,6-di-tert-butyl substituted o-phosphanylphenol silyl ethers 4. These were applied for the preparation of the corresponding o-phosphanylphenols 5, mainly P-asymmetric derivatives. Limitations and side reactions by use of 1 in the above synthesis are discussed. Acid-base properties, pH-dependent solubility in water/hexane, and substitution reactions at oxygen and phosphorus of selected representatives of 5 are reported. An example for the separation of enantiomers by esterification with (1S)-(—)-camphanic acid chloride is given. IR studies revealed intramolecular P-H—O bonds and 2J(PC) the preferred trans arrangement of the phenoxy group in solution. In the solid state, inter- and intramolecular P-H—O bonds were detected by X-ray structure analysis. The trans arrangement of the phenoxy group is preserved. Because of steric hindrance, the O substituents are tilted towards the phosphorus atom and thus induce large through-space coupling constants. The P-Sn distance of 336.9 pm in the bulky substituted O—SnMe3 moiety 8h is however too large for the formation of genuine intramolecular coordination. The versatility of o-hydroxyarylphosphanes and objectives of further studies are shown by preliminary results on complex formation and applications of these phosphanes in catalysis.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961291223
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  • 9
    Electronic Resource
    Electronic Resource
    Conformations and Dynamic Behaviour of Rhodium Complexes with 1,4-Bis(diphenylphosphanyl)butane, DIOP and Its HO Analogue (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 705-711 
    Details
    ISSN: 1434-1948
    Keywords: Conformation analysis ; Molecular modelling ; NMR spectroscopy ; Seven-membered chelates ; Rhodium ; Ab initio calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The temperature dependence of NMR spectra of [(L)Rh(cod)]BF4 complexes with L = dppb (1), (R,R)-diop (2) and (R,R)-HO-diop (3) has been examined. Molecular mechanics and ab initio calculations on the [{1,4-bis(dimethylphosphanyl)butane}Rh+(diolefin)] complex predict local energy minima for all twist-chair (TC1, TC2 = TC7, TC3 = TC6, TC4 = TC5) and two boat (B3 = B6 and TB1) conformations. Furthermore, ab initio calculations at the B3LYP/6-31G(d)/LANL2DZ level show that two minima are located in the wide-open region between the TC7 and C4 conformations. Relative B3LYP/6-31G(d) energies of the B3, TC1 and {C4-TC7} conformations are 0.0, 0.71 and 0.97-1.08 kcal mol-1, respectively. Analysis of crystallographic data contained in the Cambridge Structural Database shows that the majority of structures are concentrated in the region {C4-TC7} and close to B3. The symmetrical doublet in the 31P-NMR spectra is assigned to the fast equilibrium {TC7-C4} ⇌ TC1 ⇌ {C5-TC2}. The resonances of the other species are consistent with B3 = B6 geometry. A fused dioxolane ring forces the chelate in diop complexes to adopt the B4 = B5 conformation. For both types of ligand the chair-like conformation is enthalpically preferred at low temperatures (ΔH° = 0.45-0.46 kcal mol-1), whereas the boat-shaped structure predominates at temperatures above 200 K (ΔS° = 0.9-1.3 cal K-1 mol-1). Line-shape analysis provides a boat pseudorotation barrier for complex 1 of ΔG≠ = 5.9 kcal mol-1 and for 2 ΔG≠ = 5.3 kcal mol-1 at 184 K. The free energy of activation at this temperature for the boat-chair interconversion is ΔG≠ = 8.6 kcal mol-1 for complex 1 and ΔG≠ = 8.0 kcal mol-1 for complex 2.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Proof of Chiral Dihydride Complexes Including Catalyst and Substrate during the Bis(phosphinite)rhodium(I)-Catalyzed Hydrogenation of Dimethyl ItaconateThis work was financially supported by the Volkswagenstifung, the Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie(BMBF), the Deutsche Forschungsgemeinschaft (SFB 334: Wechselwirkungen in Molekülen), and the Fonds der Chemischen Industrie. (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 36 (1997), S. 1103-1105 
    Details
    ISSN: 0570-0833
    Keywords: homogeneous catalysis ; hydrido complexes ; NMR spectroscopy ; parahydrogen ; rhodium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199711031
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