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|Title:||Fluorous zirconium phosphonates as novel materials for catalyst separation and recovery|
|Authors:||Bennett, James Andrew|
|Presented at:||University of Leicester|
|Abstract:||Amorphous fluorous zirconium phosphonates (FZrP) with varying degrees of fluorination have been successfully synthesised and their ability to recover fluorous catalysts assessed in three catalytic systems; a dirhodium perfluorobutyrate cyclopropanation of styrene, a perfluorooctyl seleninic acid oxidation of p-nitrobenzaldehyde and a fluorous BINAP palladium catalyst enantioselective fluorination of methyl and butyl cyclopentanone-2-carboxylate.;Conversions of 60 -- 70% were attained for the cyclopropanation of styrene after 4 hours in toluene at 100Â°C using 0.017 mol% of dirhodium perfluorobutyrate. The catalyst was recovered up to 6 times in both supported and homogeneous/solid phase extraction systems, with no observable drop in activity. Rhodium leaching levels were lowest when the catalyst was supported on [Zn(O3P-C6H4-C6F13)2]. A solid-supported seleninic acid precatalyst for the oxidation of p-nitrobenzaldehyde was recycled 3 times under optimised conditions, with accumulative Se leaching of 2.0%. Conversions fell slightly over the 3 runs, from 94 to 82%. A comparison of support materials showed that, as for the rhodium system, catalyst leaching was lowest with the FZrP material, [Zr(O3P-C6H4-C6F13) 2].;In the enantioselective fluorination system, the Pd BINAP catalyst was most effectively separated and reused using a column of FZrP. The catalyst was recycled over 3 runs, with conversions over 90% and ees in excess of 88%. Due to further purification of the product by column chromatography, necessary for chiral-GC analysis, ICP-OES analysis was not performed and Pd leaching data was, therefore, unavailable for this system.|
|Rights:||Copyright © the author. All rights reserved.|
|Appears in Collections:||Theses, Dept. of Chemistry|
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