Metal-Amide Chemistry Enables Controlled Heavy-Pnictogen Reduction for Colloidal III-V Nanocrystal Synthesis

Controlling heavy-pnictogen (As, Sb) redox chemistry remains a central challenge in RoHS-compliant III-V colloidal nanocrystal synthesis. The formation of pnictide nanocrystals, where pnictogen must reach its lowest oxidation state, is significantly impeded for heavier pnictogens under typical colloidal synthesis conditions. Consequently, external electron sources are commonly employed, but such empirical one-pot activation offers limited molecular-level insight and control over elementary steps. Here, we decouple pnictogen reduction from nanocrystal synthesis and track the reduction process using ex situ XANES and multinuclear NMR spectroscopy. Distinct from conventional hydride chemistry, in the presence of oleylamine, metal-alkyl reagents act primarily as bases rather than direct reductants, generating metal-amide complexes that mediate thermally regulated pnictogen reduction through amide-to-imine oxidation. Metal cations further tune the reduction depth by competitively accepting hydride equivalents. The resulting partially reduced pnictogen complexes function as practical precursors compatible with nanocrystal syntheses in various synthetic formats, eliminating the need for additional reducing agents during nanocrystal growth. This metal-amide-mediated prereduction establishes a redox design principle for heavy pnictogens, enabling safer and tunable synthesis of pnictide semiconductor nanocrystals.