Metal carbonyl anion loaded molecular reservoir particles — application to the catalytic synthesis of two styrene oxide derivatives

Abstract

Molecular reservoirs consisting of a porous polydivinylbenzene (PDVB) nutshell surrounding polytriethylvinylbenzyl ammonium chloride (PEVAC) chains were employed to immobilize the homogeneous catalysts: [Co(CO) 4] − or [Rh(CO) 2I 2] −. The molecular reservoirs were prepared by the successive polymerization of vinylbenzyl chloride (VBC) and divinylbenzene (DVB) in a concentrated emulsion, followed by the quaternization of the encapsulated VBC chains. The immobilization was achieved via the formation of ion-pairs between the ammonium cations and the metal carbonyl anions. Two kinds of polymer-bound catalysts dispersed in water were used to catalyze the synthesis of two derivatives of styrene oxide in the presence of CO. It was found that when PDVB (PEVAC)-[Co(CO) 4] − was used, 2,5-dihydro-2-oxo-3-hydroxy-4-phenylfuran was the main product, as in the homogeneous case. When, however, PDVB(PEVAC)-[Rh(CO) 2I 2] − was employed, 2-phenyl-2-(α-styryoxyl)ethanol was obtained as the main product; in the homogeneous case, the selectivity was much lower. Both polymer-bound catalysts were used in five successive cycles at 200 psi CO and 95–98°C, and the conversion of styrene oxide was almost quantitative. The cocatalyst methyl iodide was introduced before the first cycle only. It was found that 72% of the initial Co and 94% of the initial Rh were still present in the molecular reservoirs after the five cycles. In addition to immobilizing the homogeneous catalyst, the molecular reservoir PDVB (PEVAC) also possesses some adsorption capability for the organic reactant molecules, because of its hydrophobic porous PDVB shell. This hydrophobic adsorption capability allows the styrene oxide molecules to approach the encapsulated catalytically active sites.