Metals in organic syntheses. XI. Phosphorus-31 NMR and reactivity studies on the system trans-[PtCl(CO-nhexyl)(PPh3)2]/SnCl2, an active intermediate in the catalytic hydroformylation of 1-hexene

The system trans-[PtCl(CO-n-hexyl)(PPh3)2]/SnCl2 has been investigated by 31P NMR spectroscopy. In CD2Cl2 or acetone-d6 solns. two species (in equil. with the starting Pt complex) are obsd. at low temp.: one set of signals is attributed to the complex trans-[Pt(SnCl3)(CO-n-hexyl)(PPh3)2]; the other set does not show Sn-P coupling and it is tentatively attributed to a complex having chloride bridging the Pt and Sn metal centers. Formation of the complex trans- [Pt(SnCl3)(CO-n-hexyl)(PPh3)2] is prevented when EtOH is added to the CD2Cl2 or acetone-d6 solns. Treatment of the CD2Cl2 or acetone-d6 solns. with mol. H gives n-heptanal and hydridoplatinum species; this reaction does not occur in the presence of EtOH, where only a complex having chloride bridging the Pt and Sn metal centers seems to be present. These results are discussed in connection with the catalytic cycle of olefin hydroformylation promoted by the [PtCl2(PPh3)2]/SnCl2 system.