Phenol is a valuable base chemical applied in resin and dye industry. However, it is still largely synthesized through the Hock oxidation of cumene, which suffers from harsh conditions and a mediocre atom economy.¹ Metal-catalyzed direct hydroxylation of benzene recently emerged as a more profitable synthetic approach, but only a few systems reach acceptable conversion and selectivity.² Herein, we will present a series of bimetallic hydroxo-bridged Ni^II complexes supported by classical and mesoionic N-heterocyclic carbene ligands³ which catalytically oxidize benzene to phenol using H₂O₂ as benign oxidant with competitive efficiency and higher TONs compared to the benchmark Ni catalysts. Spectroscopic and electrochemical studies suggest an electrophilic aromatic substitution pathway involving a [Ni^III(μ-O)₂Ni^III]²⁺ species, an elusive compound detected for the first time starting from a pre-formed dinuclear Ni catalyst.

[1] Weber, M.; Weber, M.; Weber, V. Ullmann’s Encyclopedia of Industrial Chemistry, Wiley‐VCH Verlag GmbH & Co. KGaA, 2020; pp. 1–20.

[2] Rajeev, A.; Balamurugan, M.; Sankaralingam, M.; ACS Catal. 2022, 12, 9953–9982.

[3] Bertini, S.; Albrecht, M. Organometallics 2020, 39, 3413–3424.