@article{21008, abstract = {C(sp2)–heteroatom couplings operating via NiI/NiIII catalysis have emerged as an alternative to canonical Pd0/PdII systems that require complex ligand architectures. Despite intensive research efforts during the past decade, catalytic methods employing this approach are still mostly confined to activated starting materials and require high catalyst loadings due to the low catalytic activity of NiI and undesired catalyst deactivation events. This article highlights recent advances in the field toward solving these long-standing challenges. We survey strategies that streamline the generation of catalytically competent NiI species from bench-stable NiII precatalysts, and discuss mechanistic studies that shed light on deactivation pathways and the rate-determining oxidative addition of aryl halides. In the final section, we highlight recently developed synthetic methodologies, which provide evidence that limitations can indeed be addressed by working at elevated temperatures, employing alternative electrophiles, harnessing the benefits of additives, or fine-tuning the metal’s reactivity through the ligand field.}, author = {Bena, Aleksander and Pieber, Bartholomäus}, issn = {2155-5435}, journal = {ACS Catalysis}, number = {2}, pages = {866--881}, publisher = {American Chemical Society}, title = {{Advances in NiI/NiIII-catalyzed C(sp2)–heteroatom cross-couplings}}, doi = {10.1021/acscatal.5c07964}, volume = {16}, year = {2026}, } @article{14663, abstract = {As a bottleneck in the direct synthesis of hydrogen peroxide, the development of an efficient palladium-based catalyst has garnered great attention. However, elusive active centers and reaction mechanism issues inhibit further optimization of its performance. In this work, advanced microkinetic modeling with the adsorbate–adsorbate interaction and nanoparticle size effect based on first-principles calculations is developed. A full mechanism uncovering the significance of adsorbate–adsorbate interaction is determined on Pd nanoparticles. We demonstrate unambiguously that Pd(100) with main coverage species of O2 and H is beneficial to H2O2 production, being consistent with experimental operando observation, while H2O forms on Pd(111) covered by O species and Pd(211) covered by O and OH species. Kinetic analyses further enable quantitative estimation of the influence of temperature, pressure, and particle size. Large-size Pd nanoparticles are found to achieve a high H2O2 reaction rate when the operating conditions are moderate temperature and higher oxygen partial pressure. We reveal that specific facets of the Pd nanoparticles are crucial factors for their selectivity and activity. Consistent with the experiment, the production of H2O2 is discovered to be more favorable on Pd nanoparticles containing Pd(100) facets. The ratio of H2/O2 induces substantial variations in the coverage of intermediates of O2 and H on Pd(100), resulting in a change in product selectivity.}, author = {Zhao, Jinyan and Yao, Zihao and Bunting, Rhys and Hu, P. and Wang, Jianguo}, issn = {2155-5435}, journal = {ACS Catalysis}, number = {22}, pages = {15054--15073}, publisher = {American Chemical Society}, title = {{Microkinetic modeling with size-dependent and adsorbate-adsorbate interactions for the direct synthesis of H₂O₂ over Pd nanoparticles}}, doi = {10.1021/acscatal.3c03893}, volume = {13}, year = {2023}, } @article{20760, abstract = {The implementation of HCN-free transfer hydrocyanation reactions on laboratory scales has recently been achieved by using HCN donor reagents under nickel- and Lewis acid co-catalysis. More recently, malononitrile-based HCN donor reagents were shown to undergo the C(sp3)–CN bond activation by the nickel catalyst in the absence of Lewis acids. However, there is a lack of detailed mechanistic understanding of the challenging C(sp3)–CN bond cleavage step. In this work, in-depth kinetic and computational studies using alkynes as substrates were used to elucidate the overall reaction mechanism of this transfer hydrocyanation, with a particular focus on the activation of the C(sp3)–CN bond to generate the active H–Ni–CN transfer hydrocyanation catalyst. Comparisons of experimentally and computationally derived 13C kinetic isotope effect data support a direct oxidative addition mechanism of the nickel catalyst into the C(sp3)–CN bond facilitated by the coordination of the second nitrile group to the nickel catalyst.}, author = {Reisenbauer, Julia and Finkelstein, Patrick and Ebert, Marc-Olivier and Morandi, Bill}, issn = {2155-5435}, journal = {ACS Catalysis}, number = {17}, pages = {11548--11555}, publisher = {American Chemical Society}, title = {{Mechanistic investigation of the nickel-catalyzed transfer hydrocyanation of alkynes}}, doi = {10.1021/acscatal.3c02977}, volume = {13}, year = {2023}, } @article{12923, abstract = {Photoredox-mediated Ni-catalyzed cross-couplings are powerful transformations to form carbon–heteroatom bonds and are generally photocatalyzed by noble metal complexes. Low-cost and easy-to-prepare carbon dots (CDs) are attractive quasi-homogeneous photocatalyst alternatives, but their applicability is limited by their short photoluminescence (PL) lifetimes. By tuning the surface and PL properties of CDs, we designed colloidal CD nano-photocatalysts for a broad range of Ni-mediated cross-couplings between aryl halides and nucleophiles. In particular, a CD decorated with amino groups permitted coupling to a wide range of aryl halides and thiols under mild, base-free conditions. Mechanistic studies suggested dynamic quenching of the CD excited state by the Ni co-catalyst and identified that pyridinium iodide (pyHI), a previously used additive in metallaphotocatalyzed cross-couplings, can also act as a photocatalyst in such transformations.}, author = {Zhao, Zhouxiang and Pieber, Bartholomäus and Delbianco, Martina}, issn = {2155-5435}, journal = {ACS Catalysis}, keywords = {Catalysis, General Chemistry}, number = {22}, pages = {13831--13837}, publisher = {American Chemical Society}, title = {{Modulating the surface and photophysical properties of carbon dots to access colloidal photocatalysts for cross-couplings}}, doi = {10.1021/acscatal.2c04025}, volume = {12}, year = {2022}, } @article{11954, abstract = {The combination of nickel and photocatalysis has unlocked a variety of cross-couplings. These protocols rely on a few photocatalysts that can only convert a small portion of visible light (<500 nm) into chemical energy. The high-energy photons that excite the photocatalyst can result in unwanted side reactions. Dyes that absorb a much broader spectrum of light are not applicable because of their short-lived singlet excited states. Here, we describe a self-assembling catalyst system that overcomes this limitation. Immobilization of a nickel catalyst on dye-sensitized titanium dioxide results in a material that catalyzes carbon–heteroatom and carbon–carbon bond formations. The modular approach of dye-sensitized metallaphotocatalysts accesses the entire visible light spectrum and allows tackling selectivity issues resulting from low wavelengths strategically. The concept overcomes current limitations of metallaphotocatalysis by unlocking the potential of dyes that were previously unsuitable.}, author = {Reischauer, Susanne and Strauss, Volker and Pieber, Bartholomäus}, issn = {2155-5435}, journal = {ACS Catalysis}, number = {22}, pages = {13269–13274}, publisher = {American Chemical Society}, title = {{Modular, self-assembling metallaphotocatalyst for cross-couplings using the full visible-light spectrum}}, doi = {10.1021/acscatal.0c03950}, volume = {10}, year = {2020}, } @article{8926, abstract = {Bimetallic nanoparticles with tailored size and specific composition have shown promise as stable and selective catalysts for electrochemical reduction of CO2 (CO2R) in batch systems. Yet, limited effort was devoted to understand the effect of ligand coverage and postsynthesis treatments on CO2 reduction, especially under industrially applicable conditions, such as at high currents (>100 mA/cm2) using gas diffusion electrodes (GDE) and flow reactors. In this work, Cu–Ag core–shell nanoparticles (11 ± 2 nm) were prepared with three different surface modes: (i) capped with oleylamine, (ii) capped with monoisopropylamine, and (iii) surfactant-free with a reducing borohydride agent; Cu–Ag (OAm), Cu–Ag (MIPA), and Cu–Ag (NaBH4), respectively. The ligand exchange and removal was evidenced by infrared spectroscopy (ATR-FTIR) analysis, whereas high-resolution scanning transmission electron microscopy (HAADF-STEM) showed their effect on the interparticle distance and nanoparticle rearrangement. Later on, we developed a process-on-substrate method to track these effects on CO2R. Cu–Ag (OAm) gave a lower on-set potential for hydrocarbon production, whereas Cu–Ag (MIPA) and Cu–Ag (NaBH4) promoted syngas production. The electrochemical impedance and surface area analysis on the well-controlled electrodes showed gradual increases in the electrical conductivity and active surface area after each surface treatment. We found that the increasing amount of the triple phase boundaries (the meeting point for the electron–electrolyte–CO2 reactant) affect the required electrode potential and eventually the C+2e̅/C2e̅ product ratio. This study highlights the importance of the electron transfer to those active sites affected by the capping agents—particularly on larger substrates that are crucial for their industrial application.}, author = {Irtem, Erdem and Arenas Esteban, Daniel and Duarte, Miguel and Choukroun, Daniel and Lee, Seungho and Ibáñez, Maria and Bals, Sara and Breugelmans, Tom}, issn = {2155-5435}, journal = {ACS Catalysis}, number = {22}, pages = {13468--13478}, publisher = {American Chemical Society}, title = {{Ligand-mode directed selectivity in Cu-Ag core-shell based gas diffusion electrodes for CO2 electroreduction}}, doi = {10.1021/acscatal.0c03210}, volume = {10}, year = {2020}, }