Two-Phase Perchlorate Activation Enabled by a Dinuclear Fe-NHC (N-Heterocyclic Carbene) Complex.

Perchlorate, initially regarded as a weakly coordinating counterion rather than a reactive oxidizing reagent due to its kinetic stability, has garnered attention for its potential in microbial systems. Under anaerobic conditions, microbes utilize perchlorate as a terminal oxidant for methane oxidation, involving two distinct stages: extraction and release of oxidizing ability. This two-phase activation process necessitates the collaborative action of multiple enzymes, a phenomenon not extensively explored in artificial systems. To address this issue, a dinuclear Fe-NHC (N-heterocyclic carbene) complex 1 was designed to enable the two-phase activation of perchlorate. Initially, complex 1 extracts the oxidative potential of perchlorate, leading to the formation of Fe(III)-O-Fe(III) complex 2 as the oxidation product. Subsequently, the extracted oxidative potential can be released by photolyzing a mixture of complex 2 and 9,10-dihydroanthracene. In contrast to the commonly observed selectivity, the homocoupling product 5 was identified as the major product in this C-H activation reaction. Further, a catalytic C-H activation reaction is initiated under anaerobic conditions to selectively form the C-C coupling product, achieving the complete two-phase activation of perchlorate using a single artificial catalyst. This work provides a new paradigm for constructing biomimetic anaerobic oxidation using kinetically inert high-valent oxygenated acid anions as oxidants.