The Stereoselective Formation of <i>trans</i>‐Cumulene through Dehalogenative Homocoupling of Alkenyl <i>gem</i>‐Dibromides on Cu(110)

Cai, Liangliang; Kang, Faming; Sun, Qiang; Gao, Wenze; Yu, Xin; Ma, Hongchao; Yuan, Chunxue; Xu, Wei

doi:10.1002/cctc.201901300

Cited by 5 publications

(6 citation statements)

References 53 publications

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“…Thus, from the results discussed above, the whole scenario can be speculated below (Figure 4e): complete debromination of C 6 Br 6 should occur on the Ag(111) surface at RT, which could then result in the formation of a C 6 ring intermediate that was not stable and broken into the C 6 chain via a ringopening process and finally polymerized into the observed organometallic polyyne. According to previous studies, the surface-stabilized carbene (=C:) could directly couple into the cumulene structure without bonding to a metal adatom, 30,31 whereas the dehalogenated terminal alkynyl group (≡C•) would form organometallic structures on metal surfaces. 32,33 Therefore, the formation of C 6 −Ag organometallic polyyne implied the individual C 6 chain should be polyynic instead of cumulenic.…”

Section: Resultsmentioning

confidence: 99%

On-Surface Debromination of C₆Br₆: C₆ Ring versus C₆ Chain

et al. 2022

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Carbon allotropes comprising sp-hybridized carbon atoms have been investigated for decades for their molecular structure. One of the unsolved mysteries is whether they should take a linear or cyclic configuration in condensed phases due to the lack of atomistic characterizations. Herein, we designed a molecule with a C6 skeleton as a model system to address this issue, which was achieved by eliminating Br atoms from hexabromobenzene (C6Br6) molecule on the Ag(111) substrate via thermal treatment. It is found that the C6 ring intermediate resulting from complete debromination is energetically unstable at room temperature based on theoretical calculations. It subsequently transforms into the C6 polyynic chain via a ring-opening process and ultimately polymerizes into the organometallic polyyne, whose triyne structural unit is revealed by bond-resolved noncontact atomic force microscopy. Theoretical calculations demonstrated an energetically favorable pathway in which the ring-opening process occurs after complete debromination of C6Br6. Our study provides a platform for the synthesis of elusive carbon-rich materials.

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Section: Resultsmentioning

confidence: 99%

On-Surface Debromination of C₆Br₆: C₆ Ring versus C₆ Chain

et al. 2022

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“…In addition, at the peripheral of ordered islands, another motif with a V shape (as highlighted by the green contour) is also observed (Figure d). According to our previous results obtained on the Au(111) and Cu(110) surfaces, , combined with a detailed comparison of the experimental topographies and dimensions with the corresponding simulated STM images (Figures e and S1) and the calculated adsorption models (Figure f,g), it is identified that the reaction products on Ag(111) are dimerized bBVBP molecules with trans - or cis -cumulene moieties. Such a dehalogenative C–C homocoupling reaction is depicted in Figure a.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 89%

“…The alkenyl gem-dibromide group, with versatile chemical reactivity, demonstrated that an elimination reaction occurs and yields terminal alkynyl bromides in solution chemistry (as shown in Scheme 1a), 20−22 while on metal surfaces (e.g., Au(111), Cu(111), and Cu(110)), sequential dehalogenation followed by C−C homocoupling occurs with the formation of a cumulene moiety. 23,24 Moreover, interestingly, on a NaCl surface, sequential dehalogenation followed by skeletal rearrangement preferentially occurs with the formation of an alkyne moiety. 25 Herein, by introducing such a complicated alkenyl gem-dibromide group on the Ag(111) and Ag(110) surfaces, respectively, from the combination of scanning tunneling microscopy (STM) imaging and density functional theory (DFT) calculations, we demonstrate that selective on-surface reactions directed by substrate lattices are achieved as shown in Scheme 1b.…”

Section: ■ Introductionmentioning

confidence: 98%

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Selective On-Surface Reactions of the Alkenyl gem-Dibromide Group Directed by Substrate Lattices

et al. 2021

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On-surface synthesis has demonstrated great advantages for atomically precise fabrication of surface-supported nanostructures that could be promising for the next generation of semiconducting materials and molecular electronic devices. The challenging and key issue in this field is to steer surface reaction pathways achieving precise synthesis. The alkenyl gem-dibromide group has been shown to have versatile chemical reactivity. Herein, by introducing such a complicated functional group on surfaces, we demonstrate that selective on-surface reactions, that is, homocoupling and hydrogen migration, could be achieved on Ag(111) and Ag(110) surfaces, respectively. The underlying mechanism of lattice-directed selectivity is revealed by extensive density functional theory (DFT) calculations on the competitive reaction pathways. Such a lattice-directed strategy would be an important means for steering on-surface reaction pathways, aiming to achieve atomically precise synthesis with high efficiency and selectivity.

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“…Different from radialenes, [ n ]cumulenes ( n = the number of cumulative double bonds in a chain of n + 1 atoms) are linear carbon chains containing three or more cumulative double bonds in which all internal atoms except for the terminal two atoms are sp-hybridized carbons, endowing them with unique structural rigidity and electronic properties . With special four atom centers and six π-electrons, [3]cumulene is the simplest cumulene system; thus, a variety of [3]cumulene-containing systems have been explored on surfaces, − where the synthetic methods mainly involve the surface-assisted dehalogenative coupling of gem -dibromides . However, 2D heteroatom-doped cumulene-based crystals on surfaces have not been reported until now because of a lack of suitable synthetic methods.…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Crystal Transition from Radialene to Cumulene on Ag(111) via Retro-[2 + 1] Cycloaddition

Liu,

Wang,

Kang

et al. 2023

J. Am. Chem. Soc.

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crystal-to-crystal transition is an important method in crystal engineering because of its ability to directly create diverse crystal materials from one crystal. However, steering a 2D singlelayer crystal-to-crystal transition on surfaces with high chemo-and stereoselectivity under ultra-high vacuum conditions is a great challenge because the transition is a complex dynamic process. Here, we report a highly chemoselective 2D crystal transition from radialene to cumulene with retention of stereoselectivity on Ag(111) via retro-[2 + 1] cycloaddition of three-membered carbon rings and directly visualize the transition process involving a stepwise epitaxial growth mechanism by the combination of scanning tunneling microscopy and non-contact atomic force microscopy. Using progression annealing, we found that isocyanides on Ag( 111) at a low annealing temperature underwent sequential [1 + 1 + 1] cycloaddition and enantioselective molecular recognition based on C−H•••Cl hydrogen bonding interactions to form 2D triaza[3]radialene crystals. In contrast, a higher annealing temperature induced the transformation of triaza[3]radialenes to generate trans-diaza[3]cumulenes, which were further assembled into 2D cumulene-based crystals through twofold N−Ag−N coordination and C−H•••Cl hydrogen bonding interactions. By combining the observed distinct transient intermediates and density functional theory calculations, we demonstrate that the retro-[2 + 1] cycloaddition reaction proceeds via the ring opening of a three-membered carbon ring, sequential dechlorination/hydrogen passivation, and deisocyanation. Our findings provide new insights into the growth mechanism and dynamics of 2D crystals and have implications for controllable crystal engineering.

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The Stereoselective Formation of trans‐Cumulene through Dehalogenative Homocoupling of Alkenyl gem‐Dibromides on Cu(110)

Cited by 5 publications

References 53 publications

On-Surface Debromination of C₆Br₆: C₆ Ring versus C₆ Chain

On-Surface Debromination of C₆Br₆: C₆ Ring versus C₆ Chain

Selective On-Surface Reactions of the Alkenyl gem-Dibromide Group Directed by Substrate Lattices

Two-Dimensional Crystal Transition from Radialene to Cumulene on Ag(111) via Retro-[2 + 1] Cycloaddition

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The Stereoselective Formation of trans‐Cumulene through Dehalogenative Homocoupling of Alkenyl gem‐Dibromides on Cu(110)

Cited by 5 publications

References 53 publications

On-Surface Debromination of C6Br6: C6 Ring versus C6 Chain

On-Surface Debromination of C6Br6: C6 Ring versus C6 Chain

Selective On-Surface Reactions of the Alkenyl gem-Dibromide Group Directed by Substrate Lattices

Two-Dimensional Crystal Transition from Radialene to Cumulene on Ag(111) via Retro-[2 + 1] Cycloaddition

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On-Surface Debromination of C₆Br₆: C₆ Ring versus C₆ Chain

On-Surface Debromination of C₆Br₆: C₆ Ring versus C₆ Chain