Palladium(I)-Bridging Allyl Dimers for the Catalytic Functionalization of CO2

In general, the chemistry of both η1-allyl and η3-allyl Pd complexes is extremely well understood; η1-allyls are nucleophilic and react with electrophiles, whereas η3-allyls are electrophilic and react with nucleophiles. In contrast, relatively little is known about the chemistry of metal complexes with bridging allyl ligands. In this work, we describe a more efficient synthetic methodology for the preparation of PdI-bridging allyl dimers and report the first studies of their stoichiometric reactivity. Furthermore, we show that these compounds can activate CO2 and that an N-heterocyclic carbene-supported dimer is one of the most active and stable catalysts reported to date for the carboxylation of allylstannanes and allylboranes with CO2.