Tandem C-H activation/arylation catalyzed by low-valent iron complexes with bisiminopyridine ligands.

Tandem C-H activation/arylation between unactivated arenes and aryl halides catalyzed by iron complexes that bear redox-active non-innocent bisiminopyridine ligands is reported. Similar reactions catalyzed by first-row transition metals have been shown to involve substrate-based aryl radicals, whereas our catalytic system likely involves ligand-centered radicals. Preliminary mechanistic investigations based on spectroscopic and reactivity studies, in conjunction with DFT calculations, led us to propose that the reaction could proceed through an inner-sphere C-H activation pathway, which is rarely observed in the case of iron complexes. This bielectronic noble-metal-like behavior could be sustained by the redox-active non-innocent bisiminopyridine ligands.

Iminosemiquinone radical ligands enable access to a well-defined redox-active Cu(II)-CF3 complex.

The reaction of a copper complex bearing iminosemiquinone ligands with a CF3(+) source provides an unprecedented Cu(II)-CF3 complex through ligand-based oxidation. Reactivity of this complex leads to nucleophilic trifluoromethylation of the ligand, suggesting an electronic interplay that results in a formal umpolung of the initial CF3(+).