High performance of a cobalt–nitrogen complex for the reduction and reductive coupling of nitro compounds into amines and their derivatives

Replacement of precious noble metal catalysts with low-cost, non-noble heterogeneous catalysts for chemoselective reduction and reductive coupling of nitro compounds holds tremendous promise for the clean synthesis of nitrogen-containing chemicals. We report a robust cobalt–nitrogen/carbon (Co–N(x)/C-800-AT) catalyst for the reduction and reductive coupling of nitro compounds into amines and their derivates. The Co–N(x)/C-800-AT catalyst was prepared by the pyrolysis of cobalt phthalocyanine–silica colloid composites and the subsequent removal of silica template and cobalt nanoparticles. The Co–N(x)/C-800-AT catalyst showed extremely high activity, chemoselectivity, and stability toward the reduction of nitro compounds with H(2), affording full conversion and >97% selectivity in water after 1.5 hours at 110°C and under a H(2) pressure of 3.5 bar for all cases. The hydrogenation of nitrobenzene over the Co–N(x)/C-800-AT catalyst can even be smoothly performed under very mild conditions (40°C and a H(2) pressure of 1 bar) with an aniline yield of 98.7%. Moreover, the Co–N(x)/C-800-AT catalyst has high activity toward the transfer hydrogenation of nitrobenzene into aniline and the reductive coupling of nitrobenzene into other derivates with high yields. These processes were carried out in an environmentally friendly manner without base and ligands.