Ni⁰/Ni^δ+ Synergistic Catalysis on a Nanosized Ni Surface for Simultaneous Formation of C–C and C–N Bonds

Abstract

Simultaneous formation of C–C/C–N bonds provides insight into the bottom-up synthesis of N-heterocycles. This work reports Ni 0 /Ni δ+ synergistic catalysis on the surface of Ni nanoparticles for the highly efficient one-pot formation of C–C/C–N bonds, affording 1,2,3,4-tetrahydroquinoline and its derivatives from 2-amino benzyl alcohol and ethanol without any addition of liquor base or external hydrogen. Ni 0 /Ni δ+ synergistic catalysis has been achieved by regulating the Ni particle size or activating the Ni surface with O 2 . In the dehydrogenation of −CH 2 –OH to −CH═O, the formation of C══C and C═N bonds via concurrent cross-condensation, and the transformation of C═C/C═N to C–C/C–N via hydrogen transfer, ethanol dehydrogenation has been found to be the rate-determining step. Reducing the Ni particle size effectively increases the number of surface Ni δ+ sites, which accelerates catalytic dehydrogenation through synergistic catalysis between surface Ni δ+ and Ni 0 sites. The number of surface Ni δ+ sites can be further increased by appropriately activating the Ni surface with O 2 .