Advances in NiI/NiIII-Catalyzed C(sp2)-Heteroatom Cross-Couplings.

C-(sp2)-heteroatom couplings operating via NiI/NiIII catalysis have emerged as an alternative to canonical Pd0/PdII systems that require complex ligand architectures. Despite intensive research efforts during the past decade, catalytic methods employing this approach are still mostly confined to activated starting materials and require high catalyst loadings due to the low catalytic activity of NiI and undesired catalyst deactivation events. This article highlights recent advances in the field toward solving these long-standing challenges. We survey strategies that streamline the generation of catalytically competent NiI species from bench-stable NiII precatalysts, and discuss mechanistic studies that shed light on deactivation pathways and the rate-determining oxidative addition of aryl halides. In the final section, we highlight recently developed synthetic methodologies, which provide evidence that limitations can indeed be addressed by working at elevated temperatures, employing alternative electrophiles, harnessing the benefits of additives, or fine-tuning the metal's reactivity through the ligand field.