Issue 13, 2002

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

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, ∼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 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 (∼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.

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

Article information

Article type
Paper
Submitted
23 Apr 2002
Accepted
07 May 2002
First published
31 May 2002

J. Chem. Soc., Perkin Trans. 1, 2002, 1523-1534

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

R. Drake, D. C. Sherrington and S. J. Thomson, J. Chem. Soc., Perkin Trans. 1, 2002, 1523 DOI: 10.1039/B203899D

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