Metals in organic syntheses VII. The isolation of trans-[Pt(COPr-n)Cl(PPh3)2] (I) and trans-[Pt(SnCl3)(COPr-n)(PPh3)2] (II), active intermediates in the hydroformylation of propene catalyzed by a [PtCl2(PPh3)2]-SnCl2 precursor. The crystal and molecular structure of complex I and a comparison with its palladium analog.