Hydrazone-derived copper(II) coordination polymer as a selective liquid-phase catalyst: Synthesis, crystal structure and performance towards benzyl alcohol oxidation

Abstract In this study, we report the synthesis and physicochemical characterization of a novel one-dimensional copper(II) coordination polymer ([Cu(L)2]n) based on 2-acetylfuranisonicotinichydrazone, as well as its catalytic activity in the liquid-phase oxidation of benzyl alcohol. Based on spectroscopic and single crystal X-ray diffraction crystallography, the Cu(II) ion is pentacoordinated, bonded to two anionic hydrazones through the N,O chelating sites, and to the N-pyridyl atom from a third ligand molecule, which provides the formation of a one-dimensional network. The coordination polymer was evaluated as homogeneous catalyst, attaining high selectivity (90.1 %) and yield (36.9 %) towards benzaldehyde under mild conditions (70 °C, 2.10 mol% and 1:1 substrate-to-oxidant molar ratio). The efficiency was attributed to the slow tuning of the catalyst’s solubility in the reaction medium during the oxidation process by commitment of the use of an adequate solvent (acetonitrile) for efficient consumption of oxidant (TBHP) and formation of benzaldehyde. Titration experiments with TBHP, as well as an inhibitory essay, have shown the possible involvement of radical and peroxo reactive pathways in the reaction mechanism. Altogether, the results demonstrates that [Cu(L)2]n is suitable for accessible and mild fine chemical processes, in alignment with the search of environmentally friendly applications for industrial purposes.