Palladium(I) carbonyl cation-catalyzed carbonylation of olefins and alcohols in concentrated sulfuric acid

A new palladium catalyst was found to exhibit high catalytic activity for c arbonylation of olefins and alcohols, cyclo-Bis(mu-carbonyl)dipalladium(I) cation (1) with bridging CO ligands is formed by reductive carbonylation of palladium sulfate, PdSO4, in concentrated H2SO4. When an olefin or alcohol is added, complex 1 changes to anew complex (2) with terminal CO ligands, and tertiary carboxylic acids are obtained in high yields at room temperatu re and atmospheric pressure of CO. IR and C-13 NMR studies suggest that com plex 2 may be tentatively formulated to be [Pd-2(CO)(2)](2+), in which the terminal CO ligands are chemically equivalent. Complex 1 is a catalyst prec ursor, and complex 2 functions as an active species for the carbonylation o f olefins and alcohols. The catalytic behavior of the palladium carbonyl ca talyst supports the recently proposed reaction mechanism involving an olefi n-metal-CO complex as an intermediate for the catalytic carbonylation of ol efins and alcohols in strongly acidic solution.