Co-based heterogeneous catalysts from well-defined complexes: synthesis and applications

α-Diimines represent a family of nitrogen chelating ligands which found various applications in homogeneous catalysis.1,2 Here we report the first example of employing these ligands for the synthesis of Co-based supported heterogeneous catalysts starting from their well-defined complexes (Figure 1). The structure of these new materials, elucidated by XRD, XPS, TEM, Raman, TPD and TPR techniques, involves the simultaneous presence of metallic Co and Co oxides nanoparticles in contact with nitrogen-doped graphene (NDGr, derived by the pyrolysis of the nitrogen ligand) in a core-shell structure. These catalysts were successfully applied to the hydrogenation of aromatic nitro compounds. The reaction proceeds with a low catalyst loading (0.5 mol %, 10 mg/mmol) affording substituted anilines in high selectivities and yields. Furthermore, a close correlation with both the amount and the type of nitrogen in the NDGr-based catalytic material was established.