Deciphering the Mechanism of the Nickel-Catalyzed Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol

Furfuryl alcohol (FOL) has been identified as a key platform chemical of interest due to its potential to be produced from biomass. The density-functional theory (DFT) has been utilized to investigate the transformation of furfural (FAL) to FOL via catalytic transfer hydrogenation (CTH) over nickel(0) complex catalysts. The reaction mechanism was initiated by coordinating the nickel complexes to either the FAL (mechanism 1) or the alcohol molecule (mechanism 2). The DFT calculations revealed that the rate-determining step of FAL to FOL hydrogenation is the hydride transfer from the α-carbon of the alcohol to the nickel atom. The present study suggests that the electron-withdrawing and electron-donating groups in the ligand moieties can tune the Gibbs free energy of the rate-determining step. We further propose a correlation between the hydride and nickel atom and the activated Gibbs free energy of the rate-determining step.