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Selective Dimerization (selective + dimerization)

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Chemistry100%

Selected Abstracts

Mono(aryloxido)Titanium(IV) Complexes and Their Application in the Selective Dimerization of Ethylene

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2009
Jean-Benoit Cazaux
Abstract We report on the synthesis of mono(aryloxido)titanium(IV) complexes of general formula {Ti[O(o -R)Ar]X3}, with X = OiPr, ArO = 2- tert -butyl-4-methylphenoxy and R = CMe3 (2a), CMe2Ph (2b) and CH2NMe2 (2c). Attempts to reach pure mono(aryloxido) complexes when R = CH2NMe(CH2Ph) (2d) or CH2N(CH2Ph)2 (2e) were unsuccessful. When R = CH2OMe, the analogous mononuclear complex was not obtained, and instead, a dinuclear complex [(2- tert -butyl-4-methyl-6-methoxymethylphenoxy) TiCl(OiPr)(,2 -OiPr)2TiCl(OiPr)2] (3) was formed. Complexes 2b and 3 were characterized by single-crystal X-ray diffraction. The former contains a tetrahedrally coordinated TiIV centre, whereas in the latter the aryloxido ligand behaves as a chelating,bridging ligand between the two, chemically very different metal centres that form two face-sharing octahedra. Different synthetic approaches starting from [Ti(OiPr)4] or [TiCl(OiPr)3] were evaluated and are discussed. The hemilabile behaviour of the aryloxido ligand resulting from reversible coordination of its side arm was studied by variable-temperature 1H NMR spectroscopy for 2c (R = CH2NMe2). Complexes 2a,d were contacted with ethylene and AlEt3 as cocatalyst. When activated with AlEt3 (3 equiv.) at 20 bar and 60 °C, complex 2c exhibits interesting activity (2100 g/gTi/h) for the selective dimerization of ethylene to 1-butene (92,% C4=; 99+% C4=1). Noticeable differences in catalyst activity were observed when the R group was modified. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

ChemInform Abstract: Selective Dimerization of 1,6-Diynes Catalyzed by Ionic Liquid-Supported Nickel Complexes in an Ionic Liquid/Toluene Biphasic System.

CHEMINFORM, Issue 25 2009
Avijit Goswami
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Rare-Earth Silylamide-Catalyzed Selective Dimerization of Terminal Alkynes and Subsequent Hydrophosphination in One Pot.

CHEMINFORM, Issue 1 2006
Kimihiro Komeyama
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Mono(aryloxido)Titanium(IV) Complexes and Their Application in the Selective Dimerization of Ethylene

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2009
Jean-Benoit Cazaux
Abstract We report on the synthesis of mono(aryloxido)titanium(IV) complexes of general formula {Ti[O(o -R)Ar]X3}, with X = OiPr, ArO = 2- tert -butyl-4-methylphenoxy and R = CMe3 (2a), CMe2Ph (2b) and CH2NMe2 (2c). Attempts to reach pure mono(aryloxido) complexes when R = CH2NMe(CH2Ph) (2d) or CH2N(CH2Ph)2 (2e) were unsuccessful. When R = CH2OMe, the analogous mononuclear complex was not obtained, and instead, a dinuclear complex [(2- tert -butyl-4-methyl-6-methoxymethylphenoxy) TiCl(OiPr)(,2 -OiPr)2TiCl(OiPr)2] (3) was formed. Complexes 2b and 3 were characterized by single-crystal X-ray diffraction. The former contains a tetrahedrally coordinated TiIV centre, whereas in the latter the aryloxido ligand behaves as a chelating,bridging ligand between the two, chemically very different metal centres that form two face-sharing octahedra. Different synthetic approaches starting from [Ti(OiPr)4] or [TiCl(OiPr)3] were evaluated and are discussed. The hemilabile behaviour of the aryloxido ligand resulting from reversible coordination of its side arm was studied by variable-temperature 1H NMR spectroscopy for 2c (R = CH2NMe2). Complexes 2a,d were contacted with ethylene and AlEt3 as cocatalyst. When activated with AlEt3 (3 equiv.) at 20 bar and 60 °C, complex 2c exhibits interesting activity (2100 g/gTi/h) for the selective dimerization of ethylene to 1-butene (92,% C4=; 99+% C4=1). Noticeable differences in catalyst activity were observed when the R group was modified. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

An in situ Generated Ruthenium Catalyst for the Tishchenko Reaction

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010
Marc-Olivier Simon
Abstract A simple and efficient catalytic system for the selective dimerization of aldehydes, the Tishchenko reaction, is described. High yields of symmetrical esters were generally achieved using an in situ generated ruthenium catalyst in association with the electron-rich and hindered cyclohexyl(diphenyl)phosphane (CyPPh2) ligand. [source]