Coordination-Sphere Control of H2 Activation and Halide-Assisted Inner-Sphere C–C Bond Formation at Formally d10 Cu(I) Centers

Abstract

How formally d10 Cu(I) centers activate H2 and channel the resulting hydride reactivity into selective C–C bond formation without conventional two-electron redox cycling remains an important mechanistic question in inorganic chemistry. Density functional theory calculations elucidate the Cu(I)-catalyzed hydrogenative coupling of alkynes with allylic chlorides. Ligand-assisted heterolytic H2 cleavage generates a Cu–H species through an endergonic, reversible pre-equilibrium, making hydride formation a key thermodynamic entry point to the productive manifold. Across a representative but limited ligand series, the H2-cleavage barrier follows a Brønsted–Evans–Polanyi-type relationship with the Gibbs energy of Cu–H formation, indicating that ligand effects are transmitted mainly through hydride stabilization within this set. Hydrocupration is the first product-committing and stereoselectivity-determining step and is governed by steric organization and σ(Cu–H) → π*(alkyne) donor–acceptor interaction. Subsequent C–C bond formation preferentially follows a chloride-assisted inner-sphere pathway rather than an outer-sphere SN2-type mechanism because chloride participation preorganizes the electrophile, reduces structural reorganization, and attenuates Pauli repulsion. These results establish how ligand environment, hydride thermodynamics, and halide coordination jointly regulate small-molecule activation and selective bond formation at formally d10 Cu(I) centers.