Investigation of Surface Alkylation Strategy in SOMC: In Situ Generation of a Silica-Supported Tungsten Methyl Catalyst for Cyclooctane Metathesis

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• 作者：Ali Hamieh ; Raju Dey ; Manoja K. Samantaray ; Safwat Abdel-Azeim ; Edy Abou-Hamad ; Yin Chen ; Jérémie D. A. Pelletier ; Luigi Cavallo ; Jean-Marie Basset
• 刊名：Organometallics
• 出版年：2016
• 出版时间：August 8, 2016
• 年：2016
• 卷：35
• 期：15
• 页码：2524-2531
• 全文大小：481K
• 年卷期：0
• ISSN：1520-6041

文摘

An efficient and potentially scalable method is described for the synthesis of the silica-supported complexes [(≡Si–O−)WMe₅] and [(≡Si–O−)WMe₂(≡CH)] obtained by in situ alkylation of the surface-grafted tungsten chloride [(≡Si–O−)WCl₅] (1). [(≡Si–O−)WCl₅] can be readily prepared by the reaction of commercially available and stable tungsten hexachloride WCl₆ with partially dehydroxylated silica at 700 °C (SiO_2-700). Further reaction with ZnMe₂ at room temperature rapidly forms a mixture of surface-alkylated tungsten complexes. They were fully characterized by microanalysis, FTIR, mass balance, and solid-state NMR (¹H, ¹³C, ¹H–¹³C HETCOR, ¹H–¹H double quantum and triple quantum) and identified as [(≡Si–O−)WMe₅] and another product, [(≡Si–O−)WMe₂(≡CH)]. The latter might have been generated by partial decomposition of the tungsten methyl chloride compound, which is formed during the stepwise alkylation of [(≡Si–O−)WCl₅]. DFT calculations were carried out to check the relative stability of the tungsten methyl chloride intermediates and the feasibility of the reaction and corroborate the experimental results. This tungsten complex and its derivative were found to be active catalysts for the metathesis of cyclooctane.