Catalytic oxidation of a model volatile organic compound (toluene) with tetranuclear Cu(II) complexes

A tetranuclear Cu(II) cubane [Cu2(μ-1κONO’:2κOO’:3κO-HL)(μ-1κONO’:2κOO’-HL)]2‧4dmf (1) derived form (2,3-dihydroxybenzylidene)-2-hydroxybenzohydrazide (H3L) was synthesized at room temperature and characterized by elemental analysis, IR spectroscopy, ESI-MS and single crystal X-ray diffraction. The known tetranuclear Cu(II) open-cubane [Cu(HL)]4‧4EtOH (2) was synthesized from the same pro-ligand following a similar method or the reported one. The different tautomeric forms (keto and enol) of the organic ligands in 1 and 2 explain their different structural features. Both complexes were screened as catalysts for the peroxidative oxidation of toluene with tert-butyl hydroperoxide, achieving benzaldehyde and o-cresol as the main products. Complex 1 exhibits the highest activity (maximum product yield of 11%). © 2021 Elsevier B.V.