Preparation and hydrogenation studies of rhodium(I) catalyst supported on polymer crystal surfaces

Abstract

AbstractIn recent years polymers have been utilized as binding sites for transition metal catalysts (e.g. crosslinked polystyrene beads). However, general problems exist with the above system. The rate of reaction depends on the presence of solvents that adequately swell the polystyrene bead in order to allow access to the catalytic sites. Differences in polarity and reactant size can inhibit diffusion into the bead. Recently a new system has been developed whereby tris(triphenyl phosphine) chlororhodium (Wilkinson's catalyst) is bound to the surface of polyethylene single crystals. Polyethylene single crystals have a very high surface to volume ratios allowing for greater ease of reaction compared to the polystyrene system. Diffusion control of the reactant poses no problem as the catalyst is bound to the surface of the crystal rather than the interior (as in the case of polystyrene beads). In addition, many solvents can be used due to the difficulty of dissolving crystalline polyethylene (except at high temperatures). The polyethylene crystals were tested for their catalyst content using neutron activation analysis. Test results showed 3.11 wt% catalyst present on the surface of the PE single crystals. Hydrogenation studies have been conducted using the PE supported catalyst system to show the potential effectiveness of the new system.