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  • Inorganic Chemistry  (5)
  • Catalysis  (2)
  • Arene ligands  (1)
  • Diastereoselective  (1)
  • 1
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Metal-π-Complexes of Benzene Derivatives, XV. Bis(η6-naphthalene)chromium(0): X-Ray Structure Determination and Investigation by Nuclear Magnetic Resonance SpectroscopyBis(η6-naphthalene)chromium(0) (2) crystallizes in the space group P21/n with two molecules in the unit cell. The ligands in individual molecules of 2 are syn-oriented. The implied presence of a center of symmetry in 2 is caused by disorder that consists in the statistical occupation by chromium atoms of two equivalent sites between the six membered ring of pairs of parallel naphthalene ligands. The 1H and 13C NMR spectra of 2 are analysed and the spectroscopic parameters are discussed with reference to the respective data of free naphthalene as well as other (η-naphthalene)metal complexes.
    Notizen: Bis(η6-naphthalin)chrom(0) (2) kristallisiert in der Raumgruppe P21/n mit zwei Molekülen in der Elementarzelle. Die Liganden in individuellen Molekülen von 2 nehmen dabei eine syn-Anordnung ein. Das Vorliegen eines Symmetriezentrums in 2 wird durch eine Fehlordnung vorgetäuscht, die darin besteht, daß in Paaren parallel angeordneter Naphthalin-Liganden linke und rechte Lücken zwischen den Sechsringen statistisch mit Chromatomen besetzt sind. Die 1H- und 13C-NMR-Spektren von 2 werden analysiert, und die spektroskopischen Parameter werden im Vergleich mit entsprechenden Daten des freien Naphthalins sowie anderer (η-Naphthalin)metall-Komplexe diskutiert.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 2
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Reactive π-Complexes of the Group VIII Transition Metals, I. (η6-Arene)(η5-2,5-dihydro-1,2,5-thiadiborol)iron: Syntheses from Bis(arene)iron and Arene-bis(ethene)ironBis(arene)iron 1a - e, (arene = p-xylene, benzene, benzotrifluoride, 1,4-difluorobenzene) react in the temperature range of -100 to -60°C with 3,4-diethyl-2,5-dihydro-2,5-dimethyl-1,2,5-thiadiborole (thiadiborolene, 2) to form reactive intermediates which decompose at -30°C and (η6-arene)(η5-thiadiborolene)iron 3a - e are obtained. Alternatively, the synthesis is achieved via arene-bis(ethene)iron 4a,c (arene = p-xylene, benzene), which is formed from 1a,c and ethene at low temperature. Reactions, spectroscopic data, and the crystal structure of (η6-benzene)(η5-thiadiborolene)iron (3c) are reported.
    Notizen: Bis(aren)eisen 1a - e (Aren = p-Xylol, Toluol, Benzol, Benzotrifluorid, 1,4-Difluorbenzol) reagieren im Temperaturbereich von - 100 bis -60°C mit 3,4-Diethyl-2,5-dihydro-2,5-di-methyl-1,2,5-thiadiborol (Thiadiborolen, 2) zu reaktiven Zwischenverbindungen, die durch Zersetzung bei -30°C (η6-Aren)(η5-thiadiborolen)eisen 3a - e ergeben. Alternativ gelingt die Synthese über Aren-bis(ethen)eisen 4a, c (Aren = p-Xylol, Benzol), welche bei tiefen Temperaturen aus 1a, c und Ethen darstellbar sind. Reaktionen, spektroskopische Daten und die Kristallstruktur von (η6-Benzol)(η5-thiadiborolen)eisen (3c) werden mitgeteilt.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 3
    ISSN: 0009-2940
    Schlagwort(e): Arene complexes ; Ruthenium compounds ; Electrophilic substitution ; Lithiation ; Catalysis ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chiral or achiral (arene)(COD)Ru complexes can be made by replacing the η6-ligands of (η4-1,5-COD)(η6-1,3,5-cyclooctatriene)Ru (1) or (η4-1,5-COD)(η6-naphthalene)Ru (2) by a suitable arene. This well known reaction has been extended to mono- and dibromoarenes and we report a novel route to substituted (arene)(COD)Ru species, utilizing (bromoarene)-(COD)Ru as starting materials. These facilitate a rapid bromine-lithium exchange reaction with nBuLi at low temperatures and the lithiated species react readily with alkyl chloroformates as electrophiles. By using chiral electrophiles [alkyl = (-)-menthyl] enantiomerically pure or diastereomeric complexes containing CO2R* groups are formed, depending on the symmetry of the original complex. A diastereomeric 1:1 mixture was separated by recrystallization. All (arene)-(COD)Ru complexes tested so far are useful as catalysts for the hydrogenation of simple alkenes at room temperature.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 4
    ISSN: 0009-2940
    Schlagwort(e): 1,3-Diborolyl complexes, bis[η5-cyclopentadienyl)cobalt] ; 1,3-Diborolane, 4,5-diisopropylidene- and 2,4,5-triisopropylidene- ; Benzo-1,3-diborafulvene ; Electrochemistry ; ESR ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: New Routes to Bis[(cyclopentadienyl)cobalt]-μ-(η5-2,3-dihydro-1,3-diborolyl) Triple-Decker Complexes by Hydrogen Shift Reactions in Derivatives of 4,5-Diisopropylidene-1,3-diborolane, 2,4,5-Triisopropylidene-1,3-diborolane, and Benzo-1,3-diborafulveneThe 31 VE dicobalt triple-decker complexes 6, 7a, 7b, c, 8a, b, and 9a, b with bridging 2,3-dihydro-1,3-diborolyl ligands are prepared. The reaction of the 1,3-diborole 1 with [(C5Me5)-Co(C2H4)2] leads to the sandwich complex 5, which is treated with [(C5H5)Co(C2H4)2] to yield unsymmetrical 6. The 4,5-diisopropylidenetrimethyl-1,3-diborolane 3 undergoes a metal-induced 1,5-hydrogen shift and reacts with [(C5H5)Co(C2H4)2] to form the triple-decker 7a. The reaction of the 2,4,5-triisopropylidene-1,3-diborolane 4 with [(C5H5)Co(C2H4)2] leads to a mixture of the triple-deckers 7b/c, formed by intermolecular hydrogen shift. The benzo-1,3-diborafulvene derivatives 2b and 2c also react with [(C5H5)Co(C2H4)2] to give the triple-decker 8b and a mixture of 9a, b. In addition, the trinuclear complex 8c is obtained in low yield. The new paramagnetic triple-decker complexes have been analyzed by NMR and ESR spectroscopic measurements as well as by electochemistry. The constitutions of 7b/c, 8b, 8c, and 9a/b have been confirmed by X-ray structure analyses. The complexes are iso-structural, the Co - Co distances range from 3.277(1) (7b/c) to 3.316(1) Å for 8c.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1321-1325 
    ISSN: 0009-2940
    Schlagwort(e): Arene Complexes ; Ruthenium ; Diastereoselective ; Reduction ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Two preparative routes are reported that give access to the racemic series of planar chiral [(arene)(COD)Ru] derivatives containing η6-bonded o-tolyl ketone or aldehyde arene units. The ketone and aldehyde functions of these have subsequently been reduced by nBuLi and PhLi, respectively. Hydrolysis converts the initially formed lithium salts into diastereomeric benzyl alcohol complexes lithium salts into diastereomeric benzyl alcohol complexes in high yields. The formation of the new stereogenic centre is diastereoselective (88% de) for the aldehyde and diastereospecific for the ketone (de 〉 99%). Due to a sterically overcrowded situation, the rotation of the chiral side chain of [(COD) (η6-o-tolyl-tert-butylphenylmethanol) Ru] (7) is hindered, as is the rotation of the phenyl and tert-butyl substituents. As a consequence, the hydroxyl group is fixed at a position close to the metal both in solution and in the solid state.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1434-1948
    Schlagwort(e): Arene complexes ; Catalysis ; Diazadiene complexes ; Iron ; Metal vapour ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Two different routes to novel [(diene)(η6-2,6-dimethylpyridine)Fe] complexes are reported, both of which utilize metal vapour reactions. The presence of two small substituents on the 2,6-position of pyridine is essential for the η6-coordination of the heterocycle. Investigations on the reactivity and stability of the [(diene)(η6-arene)Fe] complexes are presented, including those of the benzene, phosphinine, and pyridine derivatives. These investigations give some hints to the relevant factors for determining the interaction between an iron atom and a π-coordinated neutral arene ligand, and their modification by a nitrogen or a phosphorus atom. Selective substitution of the 1,5-cyclooctadiene (COD) ligand of [(COD)(η6-arene)Fe] complexes by some 1,4-diaza-1,3-diene (DAD) derivatives is possible in the case of the benzene or phosphinine arene ligands, and [(DAD)(η6-arene)Fe] complexes are formed, but all DAD derivatives tested so far cause the complete disintegration of [(COD)(η6-2,6-dimethylpyridine)Fe]. [(DAD)(η6-arene)Fe] complexes exhibit a catalytic potential, which was evaluated by experiments on the catalytic cyclodimerization of 1,3-butadiene in the presence of [(Et2AlOEt)2] as a co-catalyst. This reaction yields up to 92% of 1,5-cyclooctadiene, and an almost quantitative butadiene conversion is possible in the presence of less than 0.1% of the catalyst. Structural investigations on [(N,N′-bis(cyclohexyl)ethylenediimine)(η6-toluene)Fe] 5a reveal some details of the Fe-DAD interaction. An effective electron back-donation from occupied iron d-orbitals into the π*-LUMO of the DAD is indicated.
    Materialart: Digitale Medien
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  • 7
    ISSN: 0570-0833
    Schlagwort(e): Arene ligands ; Intermediates ; Cocondensation ; Sandwich complexes ; Synthetic methods ; Iron ; Metal atoms ; Cobalt ; Nickel ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In 1969, P. L. Timms reported the first preparative cocondensation reactions of metal vapors with organic and inorganic substrates. The use of this technique in preparative chemistry soon spread rapidly, but in recent years there has been less activity in this sector. If metal atom reactions are not utilized primarily for the formation of new products, but for the synthesis of highly reactive intermediates, a new synthetic strategy may be developed. Our aims are reaction sequences which, based on an effective cocondensation reaction, lead gradually and selectively to new substance classes. This principle can be illustrated by the example of the cocondensation products of arenes and iron, cobalt, or nickel vapor, which decompose between -70 and -50°C. The classes of products accessible by this method extend from clusters, through π-complexes, organophosphorus and organoboron cage compounds to pure organic cycloaddition products.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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