Nickel-catalyzed C-F activations enabled chemo-divergent CC formation with alkynes by chelation assistance. The judicious choice of the alkynes electronic properties allowed the selective synthesis of double-insertion aromatic homologation or alkyne mono-annulation products by C-F/C-H activation. Based on the unambiguous crystallographic characterization of an unprecedented 9-membered nickelocyclic intermediate and extensive DFT studies, a plausible mechanistic rationale was established for the selective C-F activation and the chemodivergent catalysis.

Herein we describe the synthesis of a family of aryl-Co(III)-carboxylate complexes and their reactivity with ethyl diazoacetate. Crystallographic, full spectroscopic characterization, and theoretical evidence of unique C-metalated aryl-Co(III) enolate intermediates is provided, unraveling a carboxylate-assisted formation of aryl-Co(III) masked-carbenes. Moreover, additional evidence for an unprecedented Co(III)-mediated intramolecular S2-type C-C bond formation in which the carboxylate moiety acts as a relay is disclosed. This novel strategy is key to tame the hot reactivity of a metastable Co(III)-carbene and elicit C-C coupling products in a productive manner.

Cross-coupling transformations are a powerful tool in organic synthesis. It is known that this kind of transformations undergoes 2-electron redox processes and, for this reason, silver has been nearly forgotten as catalyst for cross-couplings since silver is mainly considered as a 1-electron redox metal. Herein, we disclose effective Ag(I)-catalyzed cross-coupling transformations using bidentate aminoquinoline as a directing group towards different nucleophiles to form CC , C-N and CO bonds. DFT calculations indicate the feasible oxidative addition of L 1-I substrate via Ag(I)/Ag(III) catalytic cycle. Furthermore, ion spectroscopy experiments suggest a highly reactive aryl-Ag(III) that in absence of nucleophiles reacts to form an intermolecular cyclic product [5d-Ag(I)-CH 3 CN], which in solution forms 5a. This work proves that silver can undergo 2-electron redox processes in cross-coupling reactions like Pd and Cu.

Electronic and steric parameters influencing the stability and reactivity of aryl-Co(iii) masked carbenes have been evaluated.