Kinetic Studies on the Cobalt-Catalyzed Norbornadiene Intermolecular Pauson-Khand Reaction

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• 作者：Rafel Cabot ; Agustí ; Lledó ; Marc Revé ; s ; Antoni Riera ; Xavier Verdaguer
• 刊名：Organometallics
• 出版年：2007
• 出版时间：February 26, 2007
• 年：2007
• 卷：26
• 期：5
• 页码：1134 - 1142
• 全文大小：355K
• 年卷期：v.26,no.5(February 26, 2007)
• ISSN：1520-6041

文摘

The kinetics for the cobalt-catalyzed intermolecular Pauson-Khand reaction (PKR) between (trimethylsilyl)acetylene and norbornadiene (NBD) at a constant CO pressure has been studied by means ofin situ FT-IR. The rate dependence on catalyst and substrate concentrations was examined, and it wasfound that the process is -1.9 order with respect to CO pressure, zero order with respect to acetylene,0.3-1.2 order with respect to NBD, and 1.3 order with respect to the Co₂(CO)₈ catalyst. Catalytic reactionintermediates were examined by their corresponding metal carbonyl IR frequencies. By a one-potconsecutive Pauson-Khand experiment, the NBD-dicobalt hexacarbonyl complex was identified as acatalytically active complex. Co₄(CO)₁₂ was also studied as a catalyst source in the PKR. Analysis of thecorresponding reaction intermediates by IR demonstrated that Co₂(CO)₈ and Co₄(CO)₁₂ provide identicalintermediate profiles upon reaction with TMSC₂H. The experimental measured kinetics are consistentwith the alkene insertion being the rate-limiting step in the catalytic PKR. Finally, the effect of phosphinesubstitution on the catalyst and the use of Lewis acid additives were shown to have a deleterious effecton the reaction rate.