Two tetranuclear and two mononuclear Cu(II) complexes with arylhydrazones of malononitrile derived ligands (compounds
1–
2 and
3–
4, respectively), one trinuclear Co(II/III) complex with an arylhydrazone of acetoacetanilide (
5) and one tetranuclear Zn(II) complex of 3-(2-carboxyphenyl-hydrazone)pentane-2,4-dione (
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Two tetranuclear and two mononuclear Cu(II) complexes with arylhydrazones of malononitrile derived ligands (compounds
1–
2 and
3–
4, respectively), one trinuclear Co(II/III) complex with an arylhydrazone of acetoacetanilide (
5) and one tetranuclear Zn(II) complex of 3-(2-carboxyphenyl-hydrazone)pentane-2,4-dione (
6) were screened as potential catalysts in the peroxidative oxidation of cyclohexane by aqueous H
2O
2 in acetonitrile. The best results were attained in the presence of pyrazine-2-carboxylic acid (PCA) with
1 (26% yield, TON = 52.0) and with
2 (24%, TON = 48.0) after 4 h at 40 °C. In the presence of complexes
5 and
6, no oxygenated products were detected in the studied conditions. The employment of non-conventional conditions like supercritical carbon dioxide (scCO
2) as reaction medium or microwave (MW) irradiation was assessed for complexes
1 and
2. After 6 h in acetonitrile–scCO
2, at 50 °C and with HNO
3 as promoter, only 17% yield was achieved using
1 as catalyst, and 21% using
2. Total yields of oxygenates up to 14 (with
1) and 13% (
2) and TOFs of 56.0 and 52.0 h
−1, respectively, were obtained working under MW irradiation at 70 °C and for the much shorter time of 0.5 h.
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