New linker systems for superior immobilized catalysts

Abstract

The rigid linkers E(p-C₆H₄PPh₂)₄ (E = Si, Sn) have been synthesized from the corresponding precursors E(p-C₆H₄Br)₄ and immobilized by forming one (E = Si) or three (E = Sn) phosphonium groups that are attached to the silica support by electrostatic interactions. The remaining unquaternized phosphines are coordinated to Wilkinson-type Rh complexes. The catalyst immobilized by the rigid scaffold with three surface-bound phosphonium groups (E = Sn) displays superior catalytic activity and lifetime with respect to the hydrogenation of dodecene. This catalyst can be recycled 30 times in a batchwise manner under standardized conditions.