A Theoretical Investigation of Iron-Catalyzed Selective Hydrogenation of Nitriles to Secondary Imines

Abstract The mechanism of the transition metal iron complex [(iPr-PNP)Fe(H)Br(CO)] catalyzed reaction of selective hydrogenation of nitriles to secondary imines has been investigated with the M06-2X function. The results indicate that the reaction involves two basic processes: (i) A catalyzed p-bromobenzonitrile to benzaldimine and primary amine transformation; (ii) condensation of benzaldimine with a primary amine to afford secondary imine. The calculated barrier of transition metal-catalyzed condensation reaction of benzaldimine with a primary amine, 30.6 kcal/mol, indicates that the condensation reaction is feasible under experiment conditions. The theoretical results provide a deeper understanding of the mechanism and fully explain the experimental facts.