DFT Studies on the Silver-Catalyzed Carboxylation of Terminal Alkynes with CO2: An Insight into the Catalytically Active Species

DFT calculations on the Ag-catalyzed carboxylation of phenyl acetylene with CO2 indicate that the true catalytically active species is a CsCO3–-coordinated Ag complex rather than neutral PhCCAg conventionally considered for such a process. The energy barrier for the insertion of CO2 into the C–Ag bond of PhCCAg (28.8 kcal/mol) is higher than that of PhCCAgI– and PhCCAg­CsCO3– anions (19.0 and 23.6 kcal/mol, respectively). Such an anion as a key intermediate is the predominant feature of the carboxylation process. The electronic effect plays a crucial role in stabilizing such transition states. In addition, the presence of an organic ligand slightly hampers generation of the active species and, therefore, reduced the yield of the final carboxylation product, which was observed experimentally.