Abstract
<jats:p>We report the development of tridentate ligands that enable the Pd(II)-catalyzed nondirected C(sp2)–H deuteration of highly electron-deficient arenes under mild conditions using D2O as the deuterium source. By merging a terminal donor, a central donor, and an internal base into a single scaffold, these ligands form a well-defined catalyst system that delivers substantially superior results compared to state-of-the-art catalysts. These catalysts promote a high deuterium incorporation across a broad substrate scope with excellent functional-group tolerance and enable the late-stage labeling of structurally complex, bioactive molecules, and advanced functional materials. Beyond providing an efficient deuteration method, this work establishes tridentate ligands as a new design principle for nondirected C–H activation and highlights their potential as a promising ligand class for high-performance catalytic systems.</jats:p>