Ag2O versus Cu2O in the Catalytic Isomerization of Coordinated Diaminocarbenes to Formamidines: A Theoretical Study

DFT theoretical calculations for the Ag2O-induced isomerization process of diaminocarbenes to formamidines, coordinated to Mn(I), have been carried out. The reaction mechanism found involves metalation of an N-H residue of the carbene ligand by the catalyst Ag2O and the formation of a key transition state showing a mu-eta(2):eta(2) coordination of the formamidinyl ligand between manganese and silver, which allows a translocation process of Mn(I) and silver(I) ions between the carbene carbon atom and the nitrogen atom, before the formation of the formamidine ligand is completed. Calculations carried out using Cu2O as a catalyst instead of Ag2O show a similar reaction mechanism that is thermodynamically possible, but highly unfavorable kinetically and very unlikely to be observed, which fully agrees with experimental results.

Automated summary

DFT theoretical calculations were performed to investigate the Ag2O-induced isomerization process of diaminocarbenes to formamidines coordinated to Mn(I). The results revealed that the reaction mechanism involves the metalation of the N-H residue of the carbene ligand by Ag2O catalyst and the formation of a key transition state with mu-eta(2):eta(2) coordination between the formamidinyl ligand and manganese-silver. In contrast, calculations with Cu2O catalyst showed a similar reaction mechanism that is thermodynamically feasible but kinetically unfavorable, consistent with experimental observations.