Platinum catalyst on polysiloxane microspheres with N-chelating groups

Abstract

Elastic and durable, magnetic and non-magnetic polysiloxane microspheres containing a large number of SiOH groups were obtained by a simple and cheap emulsion process. N-chelating ligands were grafted on these microspheres by the condensation of their silanol groups with N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane. A platinum catalyst was immobilized on these microspheres. At every stage of the microspheres modification they were characterized by spectroscopy methods as well as by SEM microscopy. The catalyst appears only in the form of Pt(II) complex. The Pt(0) form was obtained by reducing this complex using sodium borohydride. The catalytic activity of the obtained catalysts was compared using model reactions, which were the hydrosilylation of phenylacetylene and hydrogenation of cinnamaldehyde. In both of these reactions the new platinum catalysts were recycled several times with the retention of their high catalytic activity. The hydrogenation of cinnamaldehyde leads to two products hydrocinnamaldehyde (HCA) and 3-phenyl-1-propanol (PP). The comparison of the rate of formation of the products with the rate of HCA and cinnamyl alcohol (CA) hydrogenation indicates that neither HCA nor CA are intermediate in the main pathway of the formation of PP.