Palladium Tetrahedron: Asymmetry |
Tetrahedron: Asymmetry, Volume 16, Issue 3, 7 February 2005, Pages 705-710 Wen-Jian Shi, Jian-Hua Xie, Qi-Lin Zhou Abstract Palladium complexes of chiral spiro phosphoramidite and phosphite ligands are effective catalysts in the asymmetric hydrovinylation of vinylarenes with ethylene. The hydrovinylation products were obtained in modest selectivity with enantioselectivities up to 92 % ee. The structures of the palladium catalysts have been analyzed by X-ray diffraction. The active catalyst contained one monodentate ligand. A kinetic resolution accompanied the isomerization of the hydrovinylation product in the reaction. |
The Journal of Supercritical Fluids, Volume 31, Issue 3, November 2004, Pages 287-294 Ibrahim Kani, Roberto Flores, John P. Fackler Jr., Aydin Akgerman Abstract Rhodium catalysts, bound to a fluoroacrylate copolymer backbone through phosphine ligands, are synthesized and shown to be soluble and active in supercritical carbon dioxide. Hydroformylation of styrene is studied using this catalyst at two different temperatures (323 and 348 K) and three different pressures (172, 207, and 241 bar). The initial mole fraction of styrene was 4.13×10−4, styrene to Rh molar ratio was 200, and hydrogen and carbon monoxide to styrene molar ratio was 160. Conversions up to almost 100 % and branched aldehyde selectivities of 95–100 % were obtained at most reaction conditions. A kinetic model is proposed based on a dissociative mechanism, which starts by dissociation of a CO ligand to produce RRh(CO)2L2. Then coordination of an olefin, insertion of hydrogen, and coordination of CO generates the alkylrhodium complex followed by CO insertion to generate the acyl complex. Finally, reductive elimination forms the aldehyde. Oxidative addition of hydrogen is proposed as the rate-controlling step. |
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Palladocarbosilane dendrimers as catalysts for the asymmetric hydrovinylation of styrene in supercritical carbon dioxide