ONIUM CHAINS SILICA AS CATALYTIC SUPPORT - APPLICATION TO HYDROFORMYLATION

Polymer chains of quaternary oniums are deposited on the surface of hydrophilic silica by the radical polymerization of water-soluble quaternary onium monomers present in a water medium which imbibes the porous silica. The modified (quaternized) silica surface which contains a small amount of water is a more suitable support than silica, since it provides anchors for the catalytic species and sites for the adsorption of reactant molecules. It is used as substrate for the immobilization of monosulfonated triphenylphosphine (DPM) and of its rhodium carbonyl complex Cl(CO)Rh(DPM)2, through an ion-exchange process. The immobilized catalytic system containing a small amount of water was employed in the hydroformylation of styrene and ethyl 10-undecenoate. The presence of ethanol in the reaction medium is necessary to achieve a high yield of aldehydes. For styrene. the ratio of the isomer to the normal aldehyde is greater than 6, while for ethyl 10-undecenoate, it is 1 8. Structural factors that affect the regioselectivities of the aldehydes are suggested as possible explanations for the above ratios. The performance of the catalyst has remained almost unchanged during several reuses. © 1993 Academic Press, Inc.