MECHANISTIC STUDY OF ACETYLENE CARBONYLATION TO ANHYDRIDES OF DICARBOXYLIC-ACIDS IN SOLUTIONS OF PALLADIUM COMPLEXES

The mechanism of the reaction that produces maleic and succinic anhydr ides from carbon monoxide and acetylene was studied in the catalytic P dBr2-LiBr-CH3CN system. The in situ study of reactivities of possible organic intermediates, the kinetic isotope effect study (for succinic and maleic anhydrides k(H)/k(D) was estimated to be 1.05 +/- 0.05 and 0.9 +/- 0.1, respectively), the study of isotope exchange, and the oxy gen effect on the process direction, revealed that maleic anhydride is most likely a key intermediate of the succinic anhydride formation. M aleic anhydride undergoes transformations through the mediation of a p alladium hydride complex. This complex was detected in the catalytic s olution at -40 degrees C with H-1 NMR (delta= -1.88 ppm, nu(1/2) = 70 Hz).