ON THE MECHANISM OF THE PLATINUM(0)-ACID CATALYZED HYDROGENATION OF ALKENES

The hydrogenation of styrene promoted by the system [Pt(C2H4)(DPPB)]/a cid is strongly affected by the nature of the solvent, the nature of t he acid co-catalyst and the Pt/acid molar ratio. The highest catalytic . activity is obtained in toluene working with methanesulfonic acid a t a Pt/acid ratio = 1. The influence of the temperature and the hydrog en pressure on the catalytic activity has also been studied. The resul ts indicate that at least two different catalytic systems operate. One of these accounts for the catalysis in the temperature range 25-35-de grees-C, while the other one is effective above 35-degrees-C. The cata lytic activity of some model compounds has been also studied. P-31-NMR spectroscopy demonstrates that the complexes [Pt(CH(CH3)(C6H5)}(CH3SO 3)(DPPB)] and [Pt(CH3SO3)2(DPPB)] are present in the low-temperature c atalytic cycle.