Synthesis, Immobilization, MAS and HR-MAS NMR of a New Chelate Phosphine Linker System, and Catalysis by Rhodium Adducts Thereof
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abstract
A new class of tridentate phosphine ligands with the general formula [MeP{(CH2)xPPh2}3]+I - (x=4, 7, 11) and [MeP(CH2PPh2) 3]+OTf-, has been synthesized and fully characterized. The linkers have been immobilized on silica with their phosphonium moieties via electrostatic interactions, and their mobility and leaching has been studied by solid-state HR-MAS (high-resolution magic angle spinning) NMR in various solvents. Immobilized Wilkinson-type rhodium complexes have been obtained by ligand exchange with the surface-bound linkers. The activities and lifetimes of the catalysts have been tested with respect to the hydrogenation of 1-dodecene. The rhodium catalyst precursor bound by the immobilized linker [MeP{(CH2)7PPh2} 3]+I- led to material with the highest activity and lifetime, and it could be recycled for 30atimes in a batchwise manner. The other catalysts show shorter lifetimes. For all catalysts the formation of rhodium nanoparticles with a narrow size distribution around 4anm has been proven. 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.