Isolation and characterization of the acyl complexes trans-[Pt(PPh3)2(COR)Cl] (R=nBU or sBu) and their relevance to the hydroformylation of linear butenes catalyzed by platinum-tin-triphenylphosphine catalytic system. Molecular structure of cis-[Pt(PPh3)2Cl(SnCl3)]

The acyl complex trans-[Pt(PPh3)2(COnBu)Cl] (A) has been synthesized by reaction of [Pt(PPh3)2Cl2] with 1-butene under 100 atm of CO at 80–100°C, in ethanol. With 2-butene rather than 1-butene under the same conditions, a mixture of the above acyl complex and of trans-[Pt(PPh3)2(COsBu)Cl] (B) was formed. Complexes A and B do not interconvert. The new acyl complexes A andB have been characterized by IR and1H NMR and 13C NMR spectroscopy. The ratio A/B increases with PPh3/Pt ratio and with temperature. The formation of two isomers when 2-butene is used involves an isomerization process which is likely to be limited to the alkyl precursor complexes. The reactivity of complexes A andB has been tested in reactions with SnCl2, H2, HCl and trans-[Pt(PPh3)2HCl]. From the reaction solutions crystals of cis-[Pt(PPh3)2Cl(SnCl3)] have been obtained. Its molecular structure has been determined by X-ray diffraction. The Pt atom hascis square planar coordination, with angular distortions due to steric factors. The strongtrans influence of the SnCl3 group is confirmed by the lengthening of thetrans Pt-P distance. The SnCl3 group has the pyramidal geometry found in all related compounds.