Formation of Organometallic Intermediate States in On‐Surface Ullmann Couplings

Barton, Dennis L.; Gao, Hailing; Held, Philipp Alexander; Studer, Armido; Fuchs, Harald; Doltsinis, Nikos L.; Neugebauer, Johannes

doi:10.1002/chem.201605802

Cited by 41 publications

(57 citation statements)

References 39 publications

(72 reference statements)

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“…As the temperature raises,a datoms stabilize these radicalsb yformation of metal organic coordination complexes, as observed in experimental studies [6][7][8] and predictedb yt heoreticala nalysis. [7,8] Recently,i tw as even possible to visualize different intermediates of the Ullmann coupling by nc-AFM with aC Of unctionalized tip. [4,8] This strategy has also been used to better describe the mechanism of other on-surface processes such as decarboxylative coupling, [9] Glaser coupling, [10] Bergmann reaction [11] and carbene coupling.…”

Section: Introductionsupporting

confidence: 54%

Aryl Triflates in On‐Surface Chemistry

Ren

Klaasen

Witteler

et al. 2020

Chemistry A European J

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The reactivity of aryl triflates in on‐surface C−C coupling is reported. It is shown that the triflate group in aryl triflates enables regioselective homo coupling with preceding or concomitant hydrodetriflation on Cu(111). Three different symmetrical π‐systems with two and three triflate functionalities were used as monomers leading to oligomeric conjugated π‐systems. The cascade, comprising different intermediates at different reaction temperatures as observed for one of the molecules, proceeds via initial removal of the trifluoromethyl sulfonyl group to give an aryloxy radical which in turn is deoxygenated to the corresponding aryl radical. Thermodynamically driven regioselective 1,2‐hydrogen atom transfer leads to a translocated aryl radical which in turn undergoes coupling. For a sterically more hindered bistriflate, where one ortho position was blocked, dehydrogenative coupling occurred at remote position with good regioselectivity. Starting materials, intermediates as well as products were analyzed by scanning tunneling microscopy. Structures and suggested mechanism were further supported by DFT calculations.

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Section: Introductionsupporting

confidence: 54%

Aryl Triflates in On‐Surface Chemistry

Ren

Klaasen

Witteler

et al. 2020

Chemistry A European J

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“…66 The formation of adatoms in reactive environments has been identified in other contexts, like the adsorption of S-containing thiols on gold, 67 or under reaction conditions by reaction−deposition−elimination cycles 68 or the identification of organometallic-like compounds as intermediates on surface C−C couplings. 61…”

Section: ■ Discussionmentioning

confidence: 99%

“…In this configuration, one of the Ni atoms from the surface is already displaced out of the equilibrium position, by 0.16 Å, and thus points toward the formation of an adatom. 61 The dimethyl coordinated phosphine is then reactive enough to start penetration into the lattice. The final step leads to the bond breaking of the third P−C bond and the full replacement of one of the Ni atoms from the surface by the P, thus becoming the seed of the nickel phosphide formation.…”

Section: The Journal Of Physical Chemistry Bmentioning

confidence: 99%

Initial Stages in the Formation of Nickel Phosphides

Garcı́a-Muelas

López

2017

J. Phys. Chem. B

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Metal phosphides have emerged as a new powerful class of materials that can be employed as heterogeneous catalysts in transformations mainly to generate new energy vectors and the valorization of renewables. Synthetic protocols based on wet techniques are available and are based on the decomposition of the organic layer decorating the nanoparticles. For nickel, the phosphine of choice is trioctylphosphine, and this leads to the formation of NiP materials. However, the temperature at which the decomposition starts has been found to depend on the quality of the nickel surface. Density functional theory, DFT, holds the key to analyze the initial steps of the formation of these phosphide materials. We have found how clean nickel surfaces, either (111) or (100), readily breaks the ligand P-C bonds. This triggers the process that leads to the replacement of a surface nickel atom by P and concomintantly forms a Ni adatom on the surface surrounded by two methyl groups, thus starting the formation of the NiP phase. The whole process requires low energies, in agreement with the low temperature found in the experiments, 150 °C. In contrast, if the surface is oxidized, the reaction does not proceed at low temperatures and oxygen vacancies need to be created first to start the P-C bond breaking on the Ni-clean patches. Our results show that the cleaner the surface is, the milder the reactions are required for the NiP formation, and thus they pave the way for gentler synthetic protocols that can improve the control of these materials.

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“…performed kinetic analysis and concluded that the polymerization reaction is a diffusion‐controlled process and follow a nucleation‐and‐growth behavior. Barton et al. indicated that the dehalogenation process was facilitated by the adatoms.…”

Section: C−x and C−h Activation Of Sp2‐carbonmentioning

confidence: 99%

On‐Surface Synthesis of One‐Dimensional Carbon‐Based Nanostructures via C−X and C−H Activation Reactions

Kang

2019

ChemPhysChem

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The past decades have witnessed the emergence of lowdimensional carbon-based nanostructures owing to their unique properties and various subsequent applications. It is of fundamental importance to explore ways to achieve atomically precise fabrication of these interesting structures. The newly developed on-surface synthesis approach provides an efficient strategy for this challenging issue, demonstrating the potential of atomically precise preparation of low-dimensional nanostructures. Up to now, the formation of various surface nanostructures, especially carbon-based ones, such as graphene nanoribbons (GNRs), kinds of organic (organometallic) chains and films, have been achieved via on-surface synthesis strategy, in which in-depth understanding of the reaction mechanism has also been explored. This review article will provide a general overview on the formation of one-dimensional carbon-based nanostructures via on-surface synthesis method. In this review, only a part of the on-surface chemical reactions (specifically, CÀ X (X=Cl, Br, I) and CÀ H activation reactions) under ultra-high vacuum conditions will be covered. CÀ X and CÀ H Activation of sp-CarbonOn-surface dehalogenative/dehydrogenative homocoupling reactions of precursors functionalized with alkynyl groups have manifested great potential for the fabrication of low-dimensional carbon-based nanostructures involving acetylenic scaffolds, such as carbyne, graphyne and graphdiyne. Sun [8] et al. reported the successful formation of one-dimensional wires with acetylenic scaffolding via on-surface CÀ Br activation of sphybridized carbon atoms. They designed and synthesized the precursor 4,4'-di(bromoethynyl)-1,1'-biphenyl (bBEBP), and then deposited it on Au(111) substrate at RT. After annealing tõ 320 K, one-dimensional chains were formed on the surface. These chains were composed of two kinds of alternating protrusions. Thus, an organometallic chain structure combined with CÀ AuÀ C was proposed (as shown in Figure 1a), with the DFT model being in good agreement with the STM image. Further annealing to~425 K leaded to Au atoms released from the organometallic chains, and consequently, CÀ C coupled molecular chains with acetylenic linkages were obtained (as shown in Figure 1b). The disappearance of dot protrusions between biphenyl groups can be observed from the STM images. Additionally, the feasibility to incorporate acetylenic scaffoldings into two-dimensional networks was also be demonstrated in this work. Liu et al. analogously synthesized graphdiyne zigzag chains and macrocycles. Statistical results showed that macrocycles were preferred to form in low coverage of organometallic intermediates. [9] These works act as a supplement to our understandings of on-surface dehalogenative homocoupling reactions, and moreover, make CÀ X activation of sp-hybridized carbon a suitable strategy to synthesize highquality nanostructures with acetylenic linkages.Glaser coupling, discovered by Glaser [10] in 1869, can also be applied to the preparation of chain structures...

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Formation of Organometallic Intermediate States in On‐Surface Ullmann Couplings

Cited by 41 publications

References 39 publications

Aryl Triflates in On‐Surface Chemistry

Aryl Triflates in On‐Surface Chemistry

Initial Stages in the Formation of Nickel Phosphides

On‐Surface Synthesis of One‐Dimensional Carbon‐Based Nanostructures via C−X and C−H Activation Reactions

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