Synergistic Effects of Earth-Abundant Metal-Metal Oxide Enable Reductive Amination of Carbonyls at 50 °C

Reductive amination of carbonyls to primary amines is of importance to the synthesis of fine chemicals; however, this reaction with heterogeneous catalysts containing earth-abundant metals under mild conditions remains scarce. Here, we show that the nickel catalyst with mixed oxidation states enables such synthesis of primary amines under low temperature (50 degrees C) and H-2 pressure (0.9 MPa). The catalyst shows activity in both water and toluene. The high activity likely results from the formation of small (ca. 4.6 nm) partially oxidized nickel nanoparticles (NPs) homogeneously anchored onto the silica and their synergistic effect. Detailed characterizations indicate stabilization of NPs through strong metal support interaction via electron donation from the metal to support. We identify that the support endowed with an amphoteric nature shows better performance. This strategy of making small metal-metal oxide NPs will open an avenue toward the rational development of efficient catalysts that would allow for other organic transformations under mild reaction conditions.

Automated summary

This study investigates the reductive amination of carbonyls to primary amines using heterogeneous catalysts containing earth-abundant metals. The researchers find that a nickel catalyst with mixed oxidation states shows high activity under low temperature and H-2 pressure, likely due to the formation of partially oxidized nickel nanoparticles homogeneously anchored onto silica. The stabilization of these nanoparticles through strong metal support interaction via electron donation from the metal to support is identified as a key factor. The study opens up a new avenue for the rational development of efficient catalysts for organic transformations under mild reaction conditions.