Selective hydroxylation of benzene to phenol via CuII(μ-O˙)CuII intermediate using a nonsymmetric dicopper catalyst

• Published in: Dalton transactions : an international journal of inorganic chemistry 2024-12
• Main Authors: Hu, Qin-Qin, Chen, Qi-Fa, Zhang, Hong-Tao, Chen, Jia-Yi, Liao, Rong-Zhen, Zhang, Ming-Tian
• Format: Article
• Language: English
• ISSN: 1477-9234; 1477-9234
• DOI: 10.1039/d4dt02872d

The one-step oxidation of benzene to phenol represents a significant and promising advancement in modern industries focused on the production of high-value-added chemical products. Nevertheless, challenges persist in achieving sufficient catalytic selectivity and preventing over-oxidation. Inspired by copper enzymes, we present a nonsymmetric dicopper complex ([CuII2(TPMAN)(μ-OH)(H2O)]3+, 1) for the selective oxidation of benzene to phenol. Utilizing H2O2 as the oxidant, complex 1 demonstrates remarkable catalytic activity (a TON of 14 000 within 29 hours) and selectivity exceeding 97%, comparable to the finest homogeneous catalyst derived from first-row transition metals. It is noteworthy that the significant substituent effect, alongside a negligible kinetic isotope effect (KIE = 1.05), radical trapping experiments, and an inconsistent standard selectivity test of the ˙OH radicals, all contradict the conventional Fenton mechanism and rebound pathway. Theoretical investigations indicate that the active CuII(μ-O˙)CuII-OH species generated through the cleavage of the O-O bond in the CuII(μ-1,1-OOH)CuI intermediate facilitates the hydroxylation of benzene via an electrophilic attack mechanism. The nonsymmetric coordination geometry is crucial in activating H2O2 and in the process of O-O bond cleavage.The one-step oxidation of benzene to phenol represents a significant and promising advancement in modern industries focused on the production of high-value-added chemical products. Nevertheless, challenges persist in achieving sufficient catalytic selectivity and preventing over-oxidation. Inspired by copper enzymes, we present a nonsymmetric dicopper complex ([CuII2(TPMAN)(μ-OH)(H2O)]3+, 1) for the selective oxidation of benzene to phenol. Utilizing H2O2 as the oxidant, complex 1 demonstrates remarkable catalytic activity (a TON of 14 000 within 29 hours) and selectivity exceeding 97%, comparable to the finest homogeneous catalyst derived from first-row transition metals. It is noteworthy that the significant substituent effect, alongside a negligible kinetic isotope effect (KIE = 1.05), radical trapping experiments, and an inconsistent standard selectivity test of the ˙OH radicals, all contradict the conventional Fenton mechanism and rebound pathway. Theoretical investigations indicate that the active CuII(μ-O˙)CuII-OH species generated through the cleavage of the O-O bond in the CuII(μ-1,1-OOH)CuI intermediate facilitates the hydroxylation of benzene via an e