TY - GEN AB - Single-atom heterogeneous catalysts (SACs) are potential, recoverable alternatives to soluble organometallic complexes for cross-coupling reactions in fine-chemical synthesis. When developing SACs for these applications, it is often expected that the need for ligands, which are essential for organometallic catalysts, can be bypassed. Contrary to that, ligands remain almost always required for palladium atoms stabilized on commonly used functionalized carbon and carbon nitride supports, as the catalysts otherwise show limited activity. Despite this, ligand optimization has received little attention, and their role in activating SACs is poorly understood. Here, we explore the impact of structurally diverse phosphine ligands on the performance of nitrogen-doped carbon supported single-atoms (Pd1@NC) in the Sonogashira–Hagihara (SH) cross-coupling reaction, using X-ray absorption spectroscopy and density functional theory simulations to rationalize the observed trends. Compared to the ligand-free SAC, SH activity is enhanced in almost all ligand-assisted systems, with reactivity varying by up to 8 orders of magnitude depending on the ligand choice. Distinct trends emerge based on the free ligand volume and ligand class. Unlike molecular systems, the electronic effects of phosphine ligands are less significant in SACs due to the modulating influence of the support. Instead, the performance of SAC-ligand systems is governed by a balance between the ligand deformation energy during coordination with metal centers, and their resulting accessibility to cross-coupling reagents. These findings offer key insights into optimizing Pd-SACs by leveraging phosphine ligands to activate metal centers and tailor the 3D environment. AD - School of Engineering and Architecture (HEIA-FR), HES-SO University of Applied Sciences and Arts Western Switzerland AD - López, Núria; The Barcelona Institute of Science and Technology (BIST), Tarragona, Spain Loveday, Olivier; The Barcelona Institute of Science and Technology (BIST), Tarragona, Spain ; Universitat Rovira i Virgili, Tarragona, Spain AD - Institute for Chemical and Bioengineering, Zurich, Switzerland AD - Swiss Norwegian Beamlines, European Synchrotron Radiation Facility, Grenoble, France AD - The Barcelona Institute of Science and Technology (BIST), Tarragona, Spain AD - Institute for Chemical and Bioengineering, Zurich, Switzerland AD - School of Engineering and Architecture (HEIA-FR), HES-SO University of Applied Sciences and Arts Western Switzerland AD - Institute for Chemical and Bioengineering, Zurich, Switzerland AU - Poier, Dario AU - Loveday, Oliver AU - Usteri, Marc Eduard AU - Stoian, Dragos AU - López, Núria AU - Mitchell, Sharon AU - Marti, Roger AU - Pérez-Ramírez, Javier CY - Washington, DC, USA DA - 2025-01 DO - 10.1021/acsnano.4c14131 DO - DOI EP - 1424-1432 ID - 15376 JF - ACS Nano KW - catalysts KW - group 15 compounds KW - ligands KW - metals KW - palladium KW - single-atom catalysis KW - cross-coupling reactions KW - Pd1@NC KW - ligand selection KW - phosphine KW - structure-performance relations KW - active-site accessibility L1 - https://arodes.hes-so.ch/record/15376/files/Poier_2025_ligand-induced_activation_single-atom_palladium_heterogeneous_catalysts_cross-coupling_reactions.pdf L2 - https://arodes.hes-so.ch/record/15376/files/Poier_2025_ligand-induced_activation_single-atom_palladium_heterogeneous_catalysts_cross-coupling_reactions.pdf L4 - https://arodes.hes-so.ch/record/15376/files/Poier_2025_ligand-induced_activation_single-atom_palladium_heterogeneous_catalysts_cross-coupling_reactions.pdf LA - eng LK - https://arodes.hes-so.ch/record/15376/files/Poier_2025_ligand-induced_activation_single-atom_palladium_heterogeneous_catalysts_cross-coupling_reactions.pdf N2 - Single-atom heterogeneous catalysts (SACs) are potential, recoverable alternatives to soluble organometallic complexes for cross-coupling reactions in fine-chemical synthesis. When developing SACs for these applications, it is often expected that the need for ligands, which are essential for organometallic catalysts, can be bypassed. Contrary to that, ligands remain almost always required for palladium atoms stabilized on commonly used functionalized carbon and carbon nitride supports, as the catalysts otherwise show limited activity. Despite this, ligand optimization has received little attention, and their role in activating SACs is poorly understood. Here, we explore the impact of structurally diverse phosphine ligands on the performance of nitrogen-doped carbon supported single-atoms (Pd1@NC) in the Sonogashira–Hagihara (SH) cross-coupling reaction, using X-ray absorption spectroscopy and density functional theory simulations to rationalize the observed trends. Compared to the ligand-free SAC, SH activity is enhanced in almost all ligand-assisted systems, with reactivity varying by up to 8 orders of magnitude depending on the ligand choice. Distinct trends emerge based on the free ligand volume and ligand class. Unlike molecular systems, the electronic effects of phosphine ligands are less significant in SACs due to the modulating influence of the support. Instead, the performance of SAC-ligand systems is governed by a balance between the ligand deformation energy during coordination with metal centers, and their resulting accessibility to cross-coupling reagents. These findings offer key insights into optimizing Pd-SACs by leveraging phosphine ligands to activate metal centers and tailor the 3D environment. PB - American Chemical Society (ACS) PP - Washington, DC, USA PY - 2025-01 SN - 1936-0851 SP - 1424-1432 T1 - Ligand-induced activation of single-atom palladium heterogeneous catalysts for cross-coupling reactions TI - Ligand-induced activation of single-atom palladium heterogeneous catalysts for cross-coupling reactions UR - https://arodes.hes-so.ch/record/15376/files/Poier_2025_ligand-induced_activation_single-atom_palladium_heterogeneous_catalysts_cross-coupling_reactions.pdf VL - 2025, 19 Y1 - 2025-01 ER -