High surface area polystyrene resin-supported Pt alkene hydrosilylation catalysts: ultimate performance and 'sting in the tail'

Two vinylbenzyl chloride (VBC)-based resins have been prepared by suspension polymerisation with a VBC feed in each of 5 vol%. A high level of divinylbenzene (DVB) has also been employed with toluene as a porogen to produce high surface areas (>600 m(2) g(-1)) in the resins. Each resin has been aminated using N,N,N'-trimethylethylenediamine and Pt loaded onto each. The so formed resin catalysts have been evaluated in the hydrosilylation of oct-1-ene using methyldichlorosilane at room temperature, and in the absence of solvent. Extensive recycling and Pt leaching studies have been carried out and the most active, selective and stable catalyst identified. Heterogeneous species with an overall performance superior to that a soluble K2PtCl6 have been produced. The results also confirm that hydrosilylation is catalysed by immobilised Pt complexes and that any concurrent alkene isomerisation is due to leached soluble Pt species. Analysis of spent resin catalyst from multiple recycling experiments has shown the presence of chemically bonded oligosiloxane arising from hydrosilylation of pendent unreacted vinyl groups in the resin followed by hydrolysis and condensation when exposed to atmospheric moisture. This fouling of the resin is however not a problem while the resin catalysts are being recycled.