Synthesis, Characterization and Catalytic Activity of New Arylhydrazones of Barbituric Acid Complexes with Co(II), Cu(II) and Ag(I)

The coordination chemistry of arylhydrazones of barbituric acids (AHBAs) is still a little explored area of research, notwithstanding their interesting chemical and structural features. Thus, these compounds have several coordination modes with a high flexibility, can exist in various tautomeric forms involving hydrogen bonds and potentially can be used as a useful tool for the construction of supramolecular architectures. Coordination compounds with such ligands are known, most of them being copper complexes and a zinc complex. To our knowledge, no examples of AHBAs complexes with cobalt(II) and silver(I) have been reported and hence the preparation of the first ones is reported herein. Moreover, there is not any application of such complexes in catalysis, i.e., peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone, which is industrial significance for the synthesis of Nylon-6,6 and caprolactams. Thus, here we report some novel complexes of Co(II), Cu(II) and Ag(I) containing AHBAs ligand and imidazole as an auxiliary ligand (Scheme). Their structure have been confirmed by analytical and spectral data (IR, 1H-NMR, 13C-NMR, ESI-MS, Elem. Anal.) and X-ray diffraction studies. Preliminary results toward their catalytic activity in oxidation of cyclohexane to a cyclohexanol and cyclohexanone mixtures are also discussed in this report.