POLY(MALEIC ACID-CO-STYRENE)-TRIRUTHENIUM CLUSTER-CATALYZED OXIDATIONOF STYRENE WITH MOLECULAR-OXYGEN

Silica-supported poly(maleic acid-co-styrene)-triruthenium clusters ha ve been prepared by carboxyl exchange of (C2H5COO)6Ru3(mu3-O)(H2O)3+C2 H5COO- with carboxyl groups of silica-supported poly(maleic acid-co-st yrene). The supported cluster displays a high activity in the oxidatio n of styrene under very mild conditions. The main product of the oxida tion is benzaldehyde which results from the oxidative cleavage of styr ene by molecular oxygen. During the catalytic reaction, the cluster on the support degrades most likely to monoruthenium species such as (ci rcled P-COO)3Ru(V)=O and (circled P-COO)3Ru(III), and the pentavalent ruthenium species may be the catalytically active species in the oxida tion. Therefore, the supported cluster could be recycled more than eig ht times without a noticeable decrease of its activity although it is already fragmented in the first cycle. A possible mechanism for the st yrene cleavage is proposed.