Improved rhodium hydrogenation catalysts immobilized on silica
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Wilkinson-type rhodium catalysts with various mono and bidentate phosphine ligands were synthesized starting from [(COD)RhCl]2 and (COD)RhCl(PPh3) as the precursors. These ligands containing an ethoxysilane group could function as linkers for immobilizing the rhodium complexes on silica and alumina. The catalytic activity of the complexes, both in homogeneous phase and immobilized, was determined using the hydrogenation of 1-dodecene, 2-cyclohexen-1-one, and 4-bromostyrene. The homogeneous and immobilized rhodium catalysts with monodentate, dppe-, and dppp-type phosphine linkers all exhibited similar activity. For the immobilized catalysts, larger average pore sizes of the support (100 Å) led to faster reactions as compared with smaller pores (e.g., 40 Å). The chelating ligands generally, even for very different metal moieties, led to diminished leaching and thus to improved stabilities and lifetimes of immobilized catalysts.
author list (cited authors)
Merckle, C., & Blümel, J.