Metal- ligand-centered reactivity of a cobalt-phenylenediamide complex with electrophiles.

A new series of [Co-CF] complexes supported by a bidentate redox-active ligand is presented. The cationic [Co-CF] complex was first obtained by reacting [CpCo(opda)] (Cp = cyclopentadienyl, opda = -phenylenediamide) with an electrophilic trifluoromethyl source, for which the redox-active phenylenediamide ligand serves as a 2e reservoir to generate [CpCp(bqdi)(CF)] (bqdi = benzoquinonediimine). Electrochemical studies of [Co-CF] revealed two reversible 1e reductions.

Redox-active ligand promoted electrophile addition at cobalt.

The reactivity of an electron-rich cobalt complex bearing an -phenylenediamide ligand with electrophilic CF and F sources is reported. These reactions lead to generation of a Co(III)-CF or Co(III)-F complex, promoted by redox-active ligand-to-substrate two-electron transfer. The rate of trifluoromethyl addition at cobalt correlates with the potential difference between the cobalt complex and the CF source.

Two-Electron Redox Tuning of Cyclopentadienyl Cobalt Complexes Enabled by the Phenylenediamide Ligand.

Achieving multielectron activity at first-row transition-metal complexes has important implications for homogeneous catalysis using earth-abundant metals. Here, we report a family of cobalt-phenylenediamide complexes that undergo reversible 2e oxidation regardless of the ligand substituents, enabling unprecedented multielectron redox tuning over 0.5 V and, in each case, affording the dicationic Co(III)-benzoquinonediimine species.

Electrooxidative para-selective C-H/N-H cross-coupling with hydrogen evolution to synthesize triarylamine derivatives.

Oxidative C-H/N-H cross-coupling is one of the most atom-economical methods for the construction of C-N bonds. However, traditional oxidative C-H/N-H cross-coupling either required the use of strong oxidants or high reaction temperature, which makes it difficult to tolerate redox active functional groups. Herein we describe an external chemical oxidant-free electrooxidative C-H/N-H cross-coupling between electron-rich arenes and diarylamine derivatives.

Aerobic Oxidative Carbonylation of Enamides by Merging Palladium with Photoredox Catalysis.

Intramolecular oxidative carbonylation reaction is an efficient approach for constructing heterocycles. However, stoichiometric amount of hypervalent metal salts is usually required in this transformation. Here we show an aerobic intramolecular oxidative carbonylation of enamides by combining palladium and photoredox catalysis.