Nickel and Palladium Catalysis: Stronger Demand than Ever

ACS Catalysis, Год журнала: 2022, Номер 12(2), С. 1180 - 1200

Опубликована: Янв. 5, 2022

Key similarities and differences of Pd Ni in catalytic systems are discussed. Overall, catalyze a vast number similar C–C C–heteroatom bond-forming reactions. However, the smaller atomic radius lower electronegativity Ni, as well more negative redox potentials low-valent species, often provide higher reactivity oxidative addition or insertion reactions persistence alkyl-Ni intermediates against β-hydrogen elimination, thus enabling activation reluctant electrophiles, including alkyl electrophiles. Another key point relates to stability open-shell electronic configurations Ni(I) Ni(III) compared with Pd(I) Pd(III). Nickel very involve interconvertible Ni(n+) active species variable oxidation states (Ni(0), Ni(I), Ni(II), Ni(III)). In contrast, involving Pd(III) still relatively less developed may require facilitation by special ligands merging photo- electrocatalysis. high Pd(n+) ensure their facile reduction Pd(0) under assistance numerous reagents solvents, providing concentrations molecular Pd1(0) complexes that can reversibly aggregate into Pdn clusters nanoparticles form cocktail Pdn(0) various nuclearities (i.e., values "n"). Ni(0) strong reductants; they sensitive deactivation air other oxidizers and, consequence, operate at catalyst loadings than palladium same The ease robustness versatility for catalysis, whereas variety enables diverse uncommon reactivity, albeit requiring efforts stabilization nickel systems. As discussion, we note easily "cocktail particles" different but (Pd1, Pdn, NPs), behave species" is stable nuclearities. Undoubtedly, there stronger demand ever not only develop improved efficient catalysts also understand mechanisms

Язык: Английский

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A reactivity model for oxidative addition to palladium enables quantitative predictions for catalytic cross-coupling reactions

Chemical Science, Год журнала: 2022, Номер 13(12), С. 3477 - 3488

Опубликована: Янв. 1, 2022

Making accurate, quantitative predictions of chemical reactivity based on molecular structure is an unsolved problem in synthesis, particularly for complex molecules. We report approach to prediction catalytic reactions structure-reactivity models a key step common many mechanisms. demonstrate this with mechanistically model the oxidative addition (hetero)aryl electrophiles palladium(0), which myriad processes. This links simple descriptors relative rates 79 substrates, including chloride, bromide and triflate leaving groups. Because often controls rate and/or selectivity palladium-catalyzed reactions, can be used make about reaction outcomes. Demonstrated applications include multivariate linear initial Sonogashira coupling successful site-selectivity Suzuki, Buchwald-Hartwig, Stille multihalogenated substrates relevant synthesis pharmaceuticals natural products.

Язык: Английский

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Pd-Catalyzed Cross-Couplings: On the Importance of the Catalyst Quantity Descriptors, mol % and ppm

Organic Process Research & Development, Год журнала: 2022, Номер 26(8), С. 2240 - 2269

Опубликована: Июль 11, 2022

This Review examines parts per million (ppm) palladium concentrations in catalytic cross-coupling reactions and their relationship with mole percentage (mol %). Most studies chemistry have historically focused on the concentration ratio between (pre)catalyst limiting reagent (substrate), expressed as mol %. Several recent papers outlined use of "ppm level" an alternative means describing reaction systems. led us to delve deeper into literature assess whether is a practically useful descriptor catalyst quantities palladium-catalyzed reactions. Indeed, we conjectured that many could, unknowingly, employed low levels" (pre)catalyst, generally, what would spread ppm look like across selection reported vast array literature. In few selected examples, examined other metal systems for comparison palladium.

Язык: Английский

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Density‐Controlled Metal Nanocluster with Modulated Surface for pH‐Universal and Robust Water Splitting

Advanced Functional Materials, Год журнала: 2023, Номер 33(12)

Опубликована: Янв. 31, 2023

Abstract Reducing the particle sizes of transition metals (TMs) and avoiding their aggregation are crucial for increasing TMs atom utilization enhancing industrial potential. However, it is still challenging to achieve uniform distributed density‐controlled nanoclusters (NCs) under high temperatures due strong interatomic metallic bonds surface energy NCs. Herein, a series NCs with controllable density nitrogen‐modulated prepared assistance selected covalent organic polymer (COP), which can provide continuous anchoring sites size‐limited skeletons. The Ir show superior hydrogen evolution reaction (HER) oxygen (OER) activities than commercial Pt/C Ir/C in both acid alkaline media. In particular, as‐prepared exhibit remarkable full water splitting performance, reaching current 10 mA cm −2 at ultralow overpotentials 1.42 1.43 V acidic electrolyte, respectively. excellent electrocatalytic attributed increased improved intrinsic activity More importantly, catalyst shows long‐term stability interaction between N‐doped carbon layer.

Язык: Английский

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Evidence for Suzuki–Miyaura cross-couplings catalyzed by ligated Pd₃-clusters: from cradle to grave

Chemical Science, Год журнала: 2024, Номер 15(8), С. 2763 - 2777

Опубликована: Янв. 1, 2024

Pd

Язык: Английский

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Oxidative Addition of (Hetero)aryl (Pseudo)halides at Palladium(0): Origin and Significance of Divergent Mechanisms

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(28), С. 19249 - 19260

Опубликована: Июль 3, 2024

Two limiting mechanisms are possible for oxidative addition of (hetero)aryl (pseudo)halides at Pd(0): a 3-centered concerted and nucleophilic displacement mechanism. Until now, there has been little understanding about when each mechanism is relevant. Prior investigations to distinguish between these pathways were limited few specific combinations the substrate ligand. Here, we computationally evaluated over 180 transition structures in order determine mechanistic trends based on substrate, ligand(s), coordination number. Natural abundance

Язык: Английский

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Different Oxidative Addition Mechanisms for 12- and 14-Electron Palladium(0) Explain Ligand-Controlled Divergent Site Selectivity

ACS Catalysis, Год журнала: 2022, Номер 12(15), С. 8822 - 8828

Опубликована: Июль 8, 2022

In cross-coupling reactions, dihaloheteroarenes are usually most reactive at C─halide bonds adjacent to a heteroatom. This selectivity has been previously rationalized. However, no mechanistic explanation exists for anomalous reports in which specific ligands effect inverted with dihalopyridines and -pyridazines. Here we provide evidence that these uniquely promote oxidative addition 12e- Pd(0). Computations indicate 14e- Pd(0) can favor different mechanisms due differences their HOMO symmetries. These shown lead site preferences, where an atypical distal nitrogen.

Язык: Английский

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Unconventional Site Selectivity in Palladium-Catalyzed Cross-Couplings of Dichloroheteroarenes under Ligand-Controlled and Ligand-Free Systems

The Journal of Organic Chemistry, Год журнала: 2022, Номер 87(11), С. 7414 - 7421

Опубликована: Май 18, 2022

Halides adjacent to nitrogen are conventionally more reactive in Pd-catalyzed cross-couplings of dihalogenated N-heteroarenes. However, a very sterically hindered N-heterocyclic carbene ligand is shown promote room-temperature cross-coupling at C4 2,4-dichloropyridines with high selectivity (∼10:1). This work represents the first highly selective method broad scope for C4-coupling these substrates where clearly under control. Under optimized conditions, diverse substituted and related compounds undergo form C4–C(sp2) C4–C(sp3) bonds using organoboron, -zinc, -magnesium reagents. The synthetic utility this highlighted multistep syntheses that combine C4-selective subsequent nucleophilic aromatic substitution reactions. majority products herein (71%) have not been previously reported, emphasizing ability methodology open up underexplored chemical space. Remarkably, we find ligand-free "Jeffery" conditions enhance Suzuki coupling by an order magnitude (>99:1). These enable C5-selective 2,5-dichloropyridine 2,5-dichloropyrimidine.

Язык: Английский

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Well-Defined Pd_n Clusters for Cross-Coupling and Hydrogenation Catalysis: New Opportunities for Catalyst Design

ACS Catalysis, Год журнала: 2022, Номер 12(19), С. 11615 - 11638

Опубликована: Сен. 9, 2022

In recent studies it has been demonstrated that the privileged reactivity of higher-order metal clusters can be exploited in widely applied catalytic processes, particularly cross-coupling reactions and hydrogenative transformations. Relatively small, well-defined Pdn have known since 1960s. Unique reactivity, reaction (product) selectivity, catalyst behavior recently uncovered, from which there is much potential design application. Ligated a smaller size (where n less than 6) may form upon degradation mononuclear Pd species en route to larger particulate (from <5 nm particles large moribund forms >1 μm range). This review presents applications clusters. We pay particular attention underlying structure clusters, linked their reactivity. A hypothesis ligated constitute mechanism by (as bridging point for monoligated through PdNPs) further discussed. Where appropriate, we mention other processes complement discussion focused on hydrogenation processes.

Язык: Английский

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We Already Know Everything about Oxidative Addition to Pd(0): Do We?

ACS Catalysis, Год журнала: 2023, Номер 13(17), С. 11399 - 11421

Опубликована: Авг. 15, 2023

The oxidative addition (OA) of organic electrophiles to Pd(0) is a fundamental step in organopalladium chemistry and plays key role palladium-catalyzed cross-coupling reactions. This perspective summarizes selected mechanistic studies the Pd(0)-to-Pd(II) OA process involving halides pseudohalides with focus on systems relevant catalytic results are organized according nature supporting ligands, extracting general trends, describing most examples. formation active species from precatalysts surveyed, as well influence different that could be present under conditions process, providing guidelines facilitate understanding improvement

Язык: Английский

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