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

Drake, R. and Sherrington, D.C. and Thomson, S.J. (2002) High surface area polystyrene resin-supported Pt catalysts in room temperature solventless octene hydrosilylation using methyldichlorosilane. Journal of the Chemical Society, Perkin Transactions 1, 2002 (13). pp. 1523-1534. ISSN 1472-7781 (http://dx.doi.org/10.1039/b203899d)

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Abstract

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, similar to500 m(2) g(-1), as determined from a BET treatment of N-2 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 Speier's 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 Speier's 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 (similar to550 m(2) g(-1)) of those studied, along with the lowest ligand and Pt contents (each similar to0.25 mmol g 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.

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