Charge-tagged polar phosphine ligands in Pd-catalysed reactions in aqueous and ionic media |
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Authors: | Vivien L van Zyl Alfred Muller D Bradley G Williams |
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Institution: | 1. Department of Chemistry, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa;2. University of Technology Sydney, School of Mathematical and Physical Sciences, P.O. Box 123, Broadway, Sydney, NSW 2007, Australia |
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Abstract: | A new range of polar imidazolium and phosphate-containing ligands was synthesised from readily available starting materials in high yielding multi-step transformations. These ligands were used to generate Pd catalysts for Suzuki and Heck C–C coupling reactions in organic and organic/aqueous media. The catalysts performed well in aqueous media in the Suzuki reaction and less well in the Heck reaction, related to substrate solubility in the aqueous media. When moving to ionic liquids, the Heck reaction dramatically improved, especially in media compatible with the polar catalysts and the non-polar reagents. In all cases, the catalysts were stable to the formation of Pd black, a form of degradation that frequently befalls Pd catalysts. The catalysts could be successfully recycled without loss of activity. |
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Keywords: | Palladium Homogeneous catalyst Ionic liquid Ligand |
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