Metal-based nanoparticles (MNPs) have been widely used as catalysts in different types of chemical transformations, taking advantage of their intrinsic properties, such as geometry, specific surface area, sites (edges, corners, faces, kinks, steps…) and electronic configuration, which offer a wide-ranging variety of interactions with the reagents and products of catalytic processes. In addition, both the nature of the metal and the support (often MNPs are supported on solids or immobilized in liquid phases) play a crucial role in their catalytic behavior and plausible recycling. Nevertheless, research works reporting on the organometallic interactions at the metal surface are much more limited, often due to the difficulty of accessing to convenient experimental techniques. In this contribution, an overview from an organometallic point of view is presented regarding the interactions of organic compounds (reactants or products) at the surface of metal nanoparticles based on experimental data and calculations, helping to establish structure-reactivity correlations. Contents 1.INTRODUCTIONDistinct metal-based nanoparticles, with dimensions in the range of 1-100 nm, have tackled a huge development over the last decades, due to their unique physical and chemical properties compared to extended materials (e.g. coordination polymers or bulk metals) or molecular-based compounds. Actually, this exclusive behavior is essentially due to structural and electronic outcomes of nanomaterials, in particular allowing widespread sorts of catalytic transformations. 1-5 Although metal nanoparticles have been largely employed in heterogeneous catalysis, specifically with significant contributions regarding the oil sector, 6 nanocatalysis emerged at the end of 1990s allowing control and fine-tuning of morphology and surface state of the as-prepared nano-objects. The advances in full characterization of nanomaterials using innovative techniques, provide a rational design of catalysts at nanometric scale. 7-10 Undoubtedly, reproducible synthetic methods affording MNPs with a tight control of structure and composition are conclusive for their applications. MNPs are commonly prepared by chemical (bottom-up) or physical (top-down) approaches.11,12Chemical methods are generally classified in colloidal synthesis, including different activation modes (conventional heating, ultrasounds, microwaves, photolysis, electrochemistry…), 12-14 and chemical vapor deposition.[15][16][17][18]Top-down procedures consist in the transformation of bulk materials into nanostructures by different ways (lase ablation, thermal activation, mechanical milling); 19-22 in particular, sputtering deposition of metal atoms or small clusters on a solid or a liquid phase seems an appropriate methodology to prepare well-defined nano-materials.11,[23][24][25]The applications of metal-based nanoparticles, including polymetallic materials, take account of a large panel of transformations. In the frame of Fine Chemistry (pharmaceuticals compounds, agrochemicals, natural products…), metal-catalyzed coupling reactions occupy a privileged position for their versatility (C-C and C-heteroatom bond formation processes, including tandem and sequential transformations).[26][27][28]These types of reactions are often multi-parameters, involving various reagents other than substrates, such as bases. Under these "cocktail" conditions, metal lixiviation from the MNP surface can occur, and thus MNPs act as reservoir of catalytically active species. 29-31 However, deep mechanistic studies have permitted to identify surface-like reactivity for different C-C or C-heteroatom couplings, exhibiting fine-tuning between the adsorption of reagents and products, permitting selective reactivity and avoiding catalyst poisoning. This review focuses on the reported works concerning C-C and C-heteroatom couplings catalyzed by MNPs, providing a special insight on metal surface-organic compounds interactions, based on experimental data including theoretical calculations, material characterization and control tests.C-C HOMO-COUPLING REACTIONSC-C bond formation transformations through metal-catalyzed homo-coupling reactions represent a useful and sustainable tool in organic synthesis. In this section, C(sp 2 )-C(sp 2 ) (Ullmann-type reactions catalyzed by Cu-, Co-, Pd-and Au-based nanoparticles) and C(sp)-C(sp) (Glaser couplings with metalbased nanoparticles from group 11) homo-couplings are reviewed, reporting mechanistic approaches in order to elucidate the role of the metal surface in the corresponding coupling. The multi-component Guerbet reaction is also discussed.Ullmann and boronic acid couplingsSymmetrical biaryl compounds are involved in a wide range of applications (rigid liquid crystals, drugs, polymers, ligands for organometallic complexes…). Many synthetic methodologies have been reported in the literature, including metal-catalyzed homocoupling approaches where palladium is mostly used but also other transition metals (copper, gold, iron…) have been efficiently applied. 32 In this frame, different reagents are used, such as aryl halides, boronic acids, arenediazonium salts and aryl organometallic compounds, among the commonest ones. One of the oldest metal-catalyzed reactions for making C-C bonds between aryl groups is the classical Cu-mediated Ullmann coupling, using aryl halides as reagents. Since the earliest works reported by Ullmann and Goldberg also including the formation of amides and ethers, 33,34 a myriad of methodologies with different transition metal catalysts has been developed to form C(sp 2 )-C(sp 2 ) and

Ekaterina Mamontova

Isabelle Favier

Category	Quartile
化学	2
化学, 有机化学	2
化学, 无机化学与核化学	2

Organometallic interactions between metal nanoparticles and carbon-based molecules: A surface reactivity rationale

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