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. Doubled up: A new dicopper complex with a dinucleating ligand, which specifically stabilizes a dinuclear structure, displays enhanced catalytic activity, selectivity, and H2O2 efficiency in the selective hydroxylation of benzene to phenol using H2O2. The dinuclear structure is favorable for the formation of the active species that specifically enhance the catalytic activity.