Emerging Trends in Cross-Coupling: Twelve-Electron-Based L 1 Pd(0) Catalysts, Their Mechanism of Action, and Selected Applications.

Monoligated palladium(0) species, L 1 Pd(0), have emerged as the most active catalytic species in the cross-coupling cycle. Today, there are methods available to generate the highly active but unstable L 1 Pd(0) catalysts from stable precatalysts. While the size of the ligand plays an important role in the formation of L 1 Pd(0) during in situ catalysis, the latter can be precisely generated from the precatalyst by various technologies. Computational, kinetic, and experimental studies indicate that all three steps in the catalytic cycle─oxidative addition, transmetalation, and reductive elimination─contain monoligated Pd. The synthesis of precatalysts, their mode of activation, application studies in model systems, as well as in industry are discussed. Ligand parametrization and AI based data science can potentially help predict the facile formation of L 1 Pd(0) species.