Specific Enhancement of Catalytic Activity by a Dicopper Core: Selective Hydroxylation of Benzene to Phenol with Hydrogen Peroxide.

A dicopper(II) complex, stabilized by the bis(tpa) ligand 1,2-bis[2-[bis(2-pyridylmethyl)aminomethyl]-6-pyridyl]ethane (6-hpa), [Cu₂(μ-OH)(6-hpa)]³⁺, was synthesized and structurally characterized. This complex catalyzed selective hydroxylation of benzene to phenol using H₂O₂, thus attaining large turnover numbers (TONs) and high H₂O₂ efficiency. The TON after 40 hours for the phenol production exceeded 12000 in MeCN at 50 °C under N₂, the highest value reported for benzene hydroxylation with H₂O₂ catalyzed by homogeneous complexes. At 22 % benzene conversion, phenol (95.2 %) and p-benzoquinone (4.8 %) were produced. The mechanism of H₂O₂ activation and benzene hydroxylation is proposed. [ABSTRACT FROM AUTHOR]