Novel Phosphinite-Ruthenium(II) complexes covalently bound on silica: Synthesis, characterization, and catalytic behavior versus oxidation reactions of alcohols into aldehydes

Duliere, E Devillers, Michel [UCL] Marchand-Brynaert, Jacqueline [UCL]

The novel tridentate phosphinite-Ru complex 5 has been prepared, characterized, and bound on silica via the spacer arm 16. The efficiency of this heterogenized catalyst for the oxidation of alcohols into aldehydes with N-methylmorpholine oxide has been examined, in comparison to the efficiency of the corresponding heterogenized monodentate phosphinite-Ru complex (without 7 and with the spacer arm 11) and the corresponding homogeneous catalysts 3 and 5, respectively. The heterogenized monodentate catalysts were 2 and 3 times more active than the soluble phosphinite-Ru complex, while the heterogenized tridentate catalyst showed almost the same activity. All catalysts are endowed with good to excellent selectivities. The heterogenized monodentate catalysts could not be efficiently recycled; on the other hand, the heterogenized tridentate catalyst 16 worked for four cycles. However, the major problem was a significant metal leaching, after the first cycle.