Novel Phosphinite−Ruthenium(II) Complexes Covalently Bound on Silica: Synthesis, Characterization, and Catalytic Behavior versus Oxidation Reactions of Alcohols into Aldehydes

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.