Nanofiltration for Homogeneous Catalysis Separation: Soluble Polymer-Supported Palladium Catalysts for Heck, Sonogashira, and Suzuki Coupling of Aryl Halides

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• 作者：Anupama Datta ; Katrin Ebert ; and Herbert Plenio
• 刊名：Organometallics
• 出版年：2003
• 出版时间：November 10, 2003
• 年：2003
• 卷：22
• 期：23
• 页码：4685 - 4691
• 全文大小：124K
• 年卷期：v.22,no.23(November 10, 2003)
• ISSN：1520-6041

文摘

The anionic polymerization of 4-methylstyrene results in a linear poly(4-methylstyrene),whose substoichiometric bromination with Br₂ converts a portion of 5-18% of the -CH₃units into -CH₂Br groups, which were then reacted with (1-Ad)₂PH to synthesize a polymerloaded with sterically demanding and electron-rich -CH₂P(1-Ad)₂ groups as the respectiveair-stable phosphonium salt. Palladium complexes with the phosphinated polymer areefficient catalysts for carbon-carbon coupling reactions of the Sonogashira, Suzuki, andHeck type with aryl chlorides and bromides. The molecular weight of the respectivephosphines in the range of 5-35 kDa does not have a significant effect on the catalyticperformance. Such polymer-enlarged catalysts are suitable for separation over a solvent-resistant nanofiltration membrane composed of a dense poly(dimethylsiloxane) (PDMS) layercast on a porous sublayer of poly(acrylonitrile) (PAN). The membrane displays virtuallyquantitative retention of the polymeric catalyst; furthermore palladium could not be foundin the permeate; TXRF and spectrophotometric determinations are indicative of >99.95%retention of the catalyst. The activity of the catalyst retained in the retentate is almostunchanged, as shown by the high (typically >90%) and almost constant yields of the couplingreactions as well as by the constant turnover frequencies of the catalysts following themembrane separation experiments during up to nine cycles of Sonogashira and Suzukireactions. For the Heck coupling the used polar aprotic solvents best suited for the catalyticreaction lead to rapid deterioration of the membranes tested.