Reversibility of palladium-alkyl intermediate formation in deuterioalkoxycarbonylation of 1-hexene

The catalytic pathways of the Pd(PPh3)2Cl2 and Pd(PPh3)2Cl2SnCl2 catalyzed 1-hexene hydroalkoxycarbonylation reaction have been elucidated. Using deuterium labelling, the different reaction products were detected by mass spectral analysis and the deuterium content and its distribution determined by 1H-, 2H- and 13C-NMR methods. The great number of labelled species in residual olefins and carbonylated products does support the assumption that the hydrido (PdH) route is operating in the mechanism of this system. Alkyl-metal intermediates undergo reversible β-hydride elimination even at low reaction temperature depending on the catalyst used.