CATALYSIS OF HYDROSILYLATION .24. H2PTCL6 IN CYCLOHEXANONE AS HYDROSILYLATION CATALYST-WHAT IS THE ACTIVE SPECIES IN THIS CATALYTIC-SYSTEM

A cyclohexanone solution of H2PtCl6 was examined to find the catalytic species responsible for the hydrosilylation of the olefinic C=C bond. Similarly to other H2PtCl6-solvent systems (e.g. Speier's and Karsted t's catalysts), the real catalyst appeared to be colloidal platinum fo rmed in situ by stepwise reduction [Pt(IV)-->Pt(O)] and dechlorination of the platinum precursor. The role of cyclohexanone seems to be to f orm sufficiently stable platinum complexes to avoid rapid platinum pre cipitation and aggregation. The studies of H2PtCl6-solvent systems are of practical importance since these compounds are widely used catalys t precursors for hydrosilylation on an industrial scale.