Summavy. Mixtures of ~-tetramethylcyclobutacliene-nickeldihali~cs and LEWIS acids such as alkylaluminiumhalides in organic solvents represent new highly active homogeneous catalysts for the dimcrization of ethylen, propene and butene under mild conditions. As a cocatalyst LEWIS bases may be used, in particular those containing trivalent phosphorous.
Szcnzmary. Mixtures of n-cyclobutadiene-nickeldihalidcs and LEWIS acids such as Al(K)nC13_,, 71. : 1-2, represent very active homogeneous catalysts for dimerization of mono-olefins. As active cocatalyst may be used LEWIS bases, in particular conipounds containing three-coordinated phosphorous (PR,). The effect of phosphines with different LEWIS-base-strength on the activity and selectivity of the catalytic system has been investigated. The kinetics of the dimerization-reaction is outlined.The mechanisms of the olefin-dimcrization is best characterized as a cdouble-cis-insertionrcactionu. The main catalytic activity is thought to be connected either to free positively charged nickel cations or to bimetallic nickel-aluminium-complexes, depending on the conditions of reaction, in particular the amount and chemical nature of the cocatalyst.A. Acide hydrazivtoe'thylphospho~ique et isothiocyavtates. Dans notre prCcCdent inCnioire 111, nous a w n s 1nont1-6 qu'en faisant r6agir I'hydrazinoCtlianol ou son monol) Senior Research Associate de la National Academy of Sciences, Washington, D.C
Summary. The kinetics of the di-and trimerization of etliylen in organic solvents under the influence of a homogeneous catalyst containing n-tetramethylcyclobutadiene-nickeldichloride and a prereacted mixture of cthylaluminiumdichloride and tri-n-butylphosphine are reported. The primary reaction product is 1-butene, which is isomerized to 2-butcne (cis/tvuns) during the reaction. The C,-Olefins are formed by the reaction of ethylene with 1-butene and with the 2-butenes. The following primary reaction products are obtained : 3-hcxenc (cis/trans), 1-hexene, 2-ethyl-1-butene, 3-methyl-1-pentene and 3-methyl-2-pentene (cisltrans) .The effect of other phosphines on the reaction was also studied. The relative composition of the reaction product is strongly dependent upon the amount and the LEWIS base strength of the phosphine present. The results are in accordance with a coordinative mechanism on nickel.
1.Einleitung. -Aus der relativen Bereitwilligkeit der Olefine Athylen, Propen und Buten zur Dimerisation und der Struktur der dabei gebildeten Primarprodukte lassen sich wertvolle Erkenntnisse iiber die Wirkungsweise der verwendeten Katalysatorsysteme gewinnen. Im Anschluss an unsere Arbeit uber die Dimerisation des Propens [l] wird hier iiber die Reaktionskinetik der Di-und Trimerisation des AtIlylens unter dern katalytischen Einfluss einer Mischung von Tetramethylcyclobutadiennickeldichlorid, [TMCBINiCl,, und einem vorreagierten Geniisch von Monoathylaluminiumdichlorid und Tri-%-Butylphosphin berichtet. Versuche mit anderen Phosphinen sollen zu vertieftem Verstandnis der aktivierenden und insbesondere der stereoregulierenden Wirkung der Phosphine im Katalysatorsystem beitragen.
The kinetics of the climerization of propene in organic solvents under the influence of a homogencous catalyst containing n-tetramethylcyclobutadiene-nickel dichloride and a prereacted mixture of ethylaluminiumdichloride and tri-n-butylphosphin are reported. The primary reaction products are : 2-methyl-1-pentene, 4-methyl-2-pentene (cisltrans), 2,3-dimethyl-l-butene and 2-Hexene (cisltrans) The results are in accordance with a coordinative mechanism on nickel. Ncw results on the reaction between ethylalutniniunidichloride and 0, N and P containing electrondonors are also discussed.
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