Synthesis, Immobilization, MAS and HR-MAS NMR of a New Chelate Phosphine Linker System, and Catalysis by Rhodium Adducts Thereof

A new class of tridentate phosphine ligands with the general formula [MePACHTUNGTRENNUNG{(CH2)xPPh2}3] I (x=4, 7, 11) and [MePACHTUNGTRENNUNG(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 [MePACHTUNGTRENNUNG{(CH2)7PPh2}3] I led to material with the highest activity and lifetime, and it could be recycled for 30 times in a batchwise manner. The other catalysts show shorter lifetimes. For all catalysts the formation of rhodium nanoparticles with a narrow size distribution around 4 nm has been proven.