Robert Drake

Polymethacrylate and polystyrene-based resin-supported Pt catalysts in room temperature, solvent-less, oct-1-ene hydrosilylations using trichlorosilane and methyldichlorosilane

Abstract A first group of methacrylate-based resins have been prepared with different amine ligands each co-ordinating Pt(II). Evaluation of each of these as room temperature catalysts in the solvent-less hydrosilylation of oct-l-ene by trichlorosilane has identified a supported ethylene diamine derived ligand as providing the most active and stable Pt catalyst. A second group of methacrylate-based resins and third group of styrene-based resins have also been prepared with a variety of morphologies. Each of these has been chemically modified to introduce the same ethylene diamine derived ligand and subsequently Pt(II) co-ordinated to each of these. Both groups of resin catalysts have been evaluated for activity, selectivity, Pt leaching and recyclability in the hydrosilylation of oct-l-ene by trichlorosilane and methyl-dichlorosilane. Specific samples of resin catalysts have been recycled up to 11 times in successive batch reactions. The styrene-based resins have been shown to be more active than the methacrylate-based ones, almost certainly because as a group they are more hydrophobic. Gel-type morphologies in the support are totally unsuitable and appear to provide severe mass transport limitations. The various macroporous resin based species are very attractive catalysts and the most likely optimum design criteria are discussed.

Remarkable activity, selectivity and stability of polymer-supported Pt catalysts in room temperature, solvent-less, alkene hydrosilylations

A polystyrene-resin supported Pt catalyst displays higher conversion, remarkably improved selectivity and excellent recyclability relative to Speier’s catalyst in the room temperature solvent-less hydrosilylation of oct-1-ene using trichlorosilane.

High surface area polystyrene resin-supported Pt catalysts in room temperature solventless octene hydrosilylation using methyldichlorosilane

Eight macroporous styrene–divinylbenzene–vinylbenzyl chloride resins have been synthesised by suspension polymerisation. The first four employed toluene as the porogen and the second four n-butyl acetate, at a level of 1 ∶ 1 v/v relative to the comonomers. In all cases a high level of divinylbenzene leads to resins with high surface area, ∼500 m2 g−1, as determined from a BET treatment of N2 sorption data. The functional group content of each group of four resins was varied from 5–25%. All resins were aminated to generate benzyltrimethylethylenediamine ligands on the polymer matrix, and then each was loaded with Pt(II) using KPtCl4. The analytical data confirmed the formation of ligand PtCl2 molecular complexes. Each of the resin immobilised Pt complexes has been assessed for catalytic activity in the room temperature, solventless, hydrosilylation of oct-1-ene using methyldichlorosilane, and a comparison made with soluble Speiers catalyst under identical conditions. Though less active than the soluble catalyst the activity of all the polymer catalysts is good, and of practical value, the activity being higher than we have previously reported in the case of supports with lower surface area. Furthermore while Speiers catalyst induces significant levels of oct-1-ene isomerisation, isomerisation in the case of the polymer catalysts is much lower, and indeed can be all but eliminated by appropriate washing. Extensive catalyst leaching and recycling studies have been carried out, with the best catalysts showing retention of useful activity after 10 cycles. Careful control experiments have provided strong circumstantial evidence that the isomerisation that does arise with the polymer catalysts can be attributed to a component of leached soluble Pt species. Overall the most active and stable polymer catalyst has the highest surface area (∼550 m2 g−1) of those studied, along with the lowest ligand and Pt contents (each ∼0.25 mmol g−1). The surface area dependence confirms our earlier view that maximum accessibility to potential metal complex catalytic sites is vital in these systems, and the metal complex loading dependence suggests that generating discrete isolated ligand PtCl2 species provides optimal use of the loaded Pt.