State of Palladium Complexes in the PdBr₂–LiBr–CH₃CN–H₂O Catalytic System, Used to Obtain Succinic Anhydride

UV–Vis spectroscopy is used to study the PdBr₂–LiBr–CH₃CN system at different concentrations of palladium and lithium bromides. The resulting data are mathematically processed using hypotheses that include the formation of monomeric and dimeric palladium complexes. Equilibrium constants of the stages of monomer and dimer complexation are calculated, along with the extinction coefficients of palladium complexes. The spectra of individual monomeric and dimeric palladium complexes are reproduced within the model, allowing for the formation of four monomeric and three dimeric complexes. UV–Vis and IR spectroscopy are used to analyze the state of palladium complexes in the PdBr₂–LiBr–CH₃CN system after contact with СО, and directly during the carbonylation of acetylene into succinic anhydride.