Aryl Triflates in On-Surface Chemistry

Article abstract of DOI:10.1002/chem.202002486

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-s

Full text of DOI:10.1002/chem.202002486

Accepted Article
Accepted Article
Title: Aryl Triflates in On-Surface Chemistry
Authors: Jindong Ren, Henning Klaasen, Melanie C. Witteler, Lena
Viergutz, Johannes Neugebauer, Hong-Ying Gao, Armido
Studer, and Harald Fuchs
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.202002486
Link to VoR: https://doi.org/10.1002/chem.202002486
01/2020

10.1002/chem.202002486
Chemistry - A European Journal
FULL PAPER
Aryl Triflates in On-Surface Chemistry
Jindong Ren,[a, b, #] Henning Klaasen,[c, #] Melanie C. Witteler,[c, d] Lena Viergutz,[c] Johannes
Neugebauer,[c, d] Hong-Ying Gao,*[a, b, e] Armido Studer*[c] and Harald Fuchs*[a, b, f]
[a]
[b]
[c]
[d]
[e]
[f]
Dr. J. Ren, Dr. H.-Y. Gao, Prof. Dr. H. Fuchs
Center for Nanotechnology (CeNTech)
Heisenbergstraße 11, 48149 Münster (Germany)
E-mail: gaoh@wwu.de, fuchsh@wwu.de
Dr. J. Ren, Dr. H.-Y. Gao, Prof. Dr. H. Fuchs
Physikalisches Institut
Westfälische Wilhelms-Universität
Wilhelm-Klemm-Straße 10, 48149 Münster (Germany)
Dr. H. Klaasen, M. C. Witteler, L. Viergutz, Prof. Dr. J. Neugebauer, Prof. Dr. A. Studer
Organisch-Chemisches Institut
Westfälische Wilhelms-Universität
Corrensstraße 40, 48149 Münster (Germany)
M. C. Witteler, Prof. Dr. J. Neugebauer
Center for Multiscale Theory and Computation
Westfälische Wilhelms-Universität
Corrensstraße 40, 48149 Münster (Germany)
Dr. H.-Y. Gao
School of Chemical Engineering and Technology
Tianjin University
Tianjin 300072 (China)
Dr. H. Fuchs
Herbert Gleiter Institute of Nanoscience
Nanjing University of Science and Technology
Xiaolingwei 200, 210094 Nanjing (P. R. China)
These authors contributed equally to this work.
[#]
Supporting information for this article is given via a link at the end of the document.
Abstract: 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 hydro-
detriflation on Cu(111). Three different symmetrical -systems with
two and three triflate functionalities were used as monomers leading
to oligomeric conjugated -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
that the energy barrier for splitting of bromine and iodine atoms from
the corresponding halogenated precursors is reduced by interaction
with the surface, with the largest impact found by the Cu(111)
surface.[3] The resulting radicals are usually expected to be stabilized
by bonding to the supporting surface[3,4] or to halogen adatoms[5] that
are adsorbed between surface and this reactive intermediate. As the
temperature raises, adatoms stabilize these radicals by formation of
metal organic coordination complexes, as observed in experimental
studies[6-8] and predicted by theoretical analysis.[7,8] Recently, it was
even possible to visualize different intermediates of the Ullmann
coupling by nc-AFM with a CO functionalized 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.[12] In order to expand the
scope of the Ullmann coupling, variations of the reactive starting unit
have been disclosed. For example, coupling reactions of organic
halides that vary in carbon hybridization state have been developed[13]
and the reactivity of aryl chlorides was investigated.[14] However, aryl
triflates, which show a similar reactivity as aryl halides in transition
metal catalysed coupling processes in solution, have so far not been
studied in on-surface chemistry. Due to their ready preparation, we
regarded them as interesting starting materials also for on-surface
chemistry.
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 analysed by scanning tunneling microscopy.
Structures and suggested mechanism were further supported by DFT
calculations.
Introduction
The identification of novel reactive functionalities is key for the further
development of on-surface chemistry.[1] Considering the on-surface
activation of -bonds, C–X bonds in aryl halides have found particular
attention. Especially, the mechanism of the Ullmann coupling[2]
comprising such an aryl–X activation is well understood. It was found
Herein we present the on-surface self-assembly behaviour and
reactivity of three different aryl triflates TPTB 1 (1,3,5-tris (phenyl-4-
trifluoromethylsulfonate)benzene),
BDBT 2
(biphenyl-4,4'-diyl
bis(trifluoromethylsulfonate)) and QDBT 3 (m-quaterphenyl-4’,6’’-diyl-
bis(trifluoromethylsulfonate)) on the Cu(111) surface (Scheme 1a). It
1
This article is protected by copyright. All rights reserved.

10.1002/chem.202002486
Chemistry - A European Journal
FULL PAPER
radicals R1 (Fig. 1b and c) that have previously been generated
from phenols on Au(111) and Ag(111) surfaces.[15] In lateral
measurement a distance of 0.86 ± 0.05 nm between a central
benzene ring and the connecting point to a neighbouring molecule
was found (for method and corresponding line profiles of all
distance measurements concerning TPTB 1 see Fig. S2). This
distance and the angle at the connecting points led to the
assumption that the oxygen atom in aryloxy radicals R1 bind to
Cu adatoms which could stabilize the structure. This model was
also investigated by DFT calculations and the expected distance
of 0.83-0.86 nm between a central benzene ring and a Cu adatom
fits the experimental data very well (Fig. S3).
Further annealing of the sample at 405 K led to a hexagonal
honeycomb lattice (Fig. 1d). The high-resolution STM image
revealed the molecular arrangement depicted in Fig. 1e. Between
the molecules a circular protrusion connecting the adjacent
molecular units could be distinguished and ascribed to Cu
adatoms.[16] The angle of 180° at the connecting moieties
supported the assumption that the C–O bond was cleaved leading
to aryl radicals R2 (Fig. 1f) connected by adatoms. Unlike
reported aryloxy radical C−C couplings on Au(111) and
Ag(111),[15] deoxygenation of the aryloxy radical on Cu(111) is
faster than ortho homocoupling. The existence of Cu adatom
stabilized radicals R2 was further supported by distance
measurement between two central benzene rings in the observed
STM line profile, which was measured to be 1.49 ± 0.05 nm fitting
the proposed structure well (Fig. S4). Notably, individual
deoxygenated aryl radicals R3 (Fig. 1i) most probably stabilized
by tilting and binding to the surface were also observed within the
pores of the honeycomb structure. These could either be radicals
R2 unattached to adatoms, or, similar to previously reported work,
translocated m-arylphenylradicals originating from
hydrogen atom transfer (HAT).[17]
a
1,2-
Scheme 1. Monomers used in the present study as well as observed reactivity.
is shown that the triflate moiety under ultra-high vacuum (UHV)
conditions undergoes ortho homocoupling, as investigated by
scanning tunnelling microscopy (STM) (Scheme 1b). Concomitant
with the C-C coupling, removal of the triflate moiety (hydrodetriflation)
is occurring. If the sterically more hindered ortho substituted QDBT 3
is used, remote C–H functionalization at neighbouring phenyl
substituents was observed as dominant reaction pathway. Upon
annealing, linear polymer chains were formed resulting from a
templating effect of the remaining triflate fragments that can be
removed after the coupling reactions under comparably mild
conditions, demonstrating the potential of bis and tris(triflates) as
monomers in surface assisted polymerization.
Upon further annealing at 440 K for 20 min, individual aryl radicals
of type R3 were found to be the dominant species at the surface
in a self-assembly (a = b = 1.67 ± 0.05 nm,  = 60 ± 0.5°) arranged
in parallel pointing in the same direction with no adatoms being
identified (Fig. 1g). The intermolecular distance between the
phenyl rings located at the nodes was measured to be
0.98 ± 0.05 nm. In a theoretical model containing three molecules
of R3 type coordinating to a Cu atom, the distance between the
same phenyl rings was found to be 0.58-0.59 nm. Further, in a
model conceived on the basis of the experimental distances
containing a Cu adatom, the C–Cu bond length would exceed the
calculated bond length of 0.20-0.21 nm by more than 0.2 nm,
further supporting the absence of adatoms in the structure formed
at 440 K (for calculations and extended discussion see Fig. S5).
In the high-resolution image, the observed distorted topography
indicates the proposed 1,2-HAT (Fig. 1h).
Results and Discussion
To support our assumption of the translocation in triradical R3, the
adsorption geometry was carefully investigated (Fig. S6). The
four possible combinations of the radical centres being either in
para or in meta position were calculated and the corresponding
total energies and adsorption energies were compared. The
calculations revealed that the most stable conformation is
achieved when all radicals are localized at the meta position. All-
meta-R3 is 81 kJ/mol more stable in comparison to all-para-R3
and also the adsorption on the Cu(111) surface is about 75 kJ/mol
stronger. As the surface coverage remained unaltered during
annealing and both phases coexist afterwards, it is highly likely
We first tested TPTB 1 (the syntheses of all triflates are described
in the ESI) on the Cu(111) surface at different annealing
temperatures (Fig. 1). After deposition at room temperature
(300 K) with a base pressure of 4.5x10-10 mbar and cooling to
78 K for STM analysis, disordered self-assembled structures
were formed (Fig. S1). Upon annealing at 370 K formation of a
C3-symmetric structure made of six molecules in its unit cell
(a = b = 2.45 ± 0.06 nm,  = 60 ± 0.5°) and Y shaped pores was
observed (Fig. 1a). Within the hexameric units two orientations of
the molecules were found, where every second molecule is
rotated by 30°. As this structure contains smaller adsorbates, an
activation of the triflate functionality is proposed leading to aryloxy
2
This article is protected by copyright. All rights reserved.

10.1002/chem.202002486
Chemistry - A European Journal
FULL PAPER
(a)
(d)
(g)
10 nm
10 nm
10 nm
(b)
(e)
(h)
1 nm
1 nm
1 nm
(c)
(f)
(i)
R3
R1
R2
Figure 1. STM topographies of organometallic structures constructed by TPTB 1 on Cu(111) surface at different annealing temperatures. (a) Overview and (b) high-
resolution STM image recorded after annealing at 370 K for 20 min. (c) Proposed structure observed in (a) and (b). (d) Overview and (e) high-resolution STM image
recorded after annealing at 405 K for 20 min. (f) Proposed structure observed in (d) and (e). (g) Overview and (h) high-resolution STM image recorded after annealing
at 440 K for 20 min. (i) Proposed structure observed in (g) and (h). Chemical sketches represent the respective dominantly formed radical species that are stabilized
by bonding to the substrate or adatoms. All STM images were acquired with a tunneling current of I = –0.2 nA and a voltage of Vb = –2.0 V.
that the radicals R3 were gradually generated from Cu adatom
stabilized radicals R2.
the 1,2-HAT is an efficient process at temperatures between
440 K and 470 K. Thus, a variation of the known ortho coupling of
phenols that is so far restricted to Au(111) and Ag(111) surfaces
has been performed at the Cu(111) surface.[15] For the reported
phenol coupling on Au(111) and Ag(111) surfaces, C−C bond
formation was suggested to occur prior to C−O cleavage as
supported by calculations. This is unlike the current case on
Cu(111) starting with triflates, where deoxygenation occurs prior
At even higher temperature (470 K), oligomerization was
observed (Fig. 2). As can be seen in the overview image,
rearranged aryl radicals engaged in coupling reactions and
disordered oligomers were formed (Fig. 2a). The high-resolution
STM images show that the molecules are even closer together
than in the organometallic network, suggesting covalent bond
formation via radical/radical coupling (Figs. 2b and c). Distance
measurement of the formed macrocycle (Fig. 2b) revealed a
diameter of 0.84 nm ± 0.06 nm in good agreement with the
structure optimized by DFT calculations (0.85 nm and 0.87 nm)
(Fig. S7). Notably, the molecules were connected ortho to the
former triflate groups with excellent regioselectivity showing that
to C−C coupling and regioselectivity is based on
a
thermodynamically favoured 1,2-H shift. It is currently not
understood why the C−C coupling in these aryl radicals did not
occur from the non-rearranged radicals derived from R2. Notably,
using
a meta derivative of TPTB 1, 1,3,5-tris (phenyl-3-
trifluoromethylsulfonate)benzene, it was not possible to perform
3
This article is protected by copyright. All rights reserved.

10.1002/chem.202002486
Chemistry - A European Journal
FULL PAPER
the same reaction cascade. While the structures observed on
surface do not change at temperatures between 370 K and 440 K,
decomposition was observed at 470 K (Fig. S8). We also tested
the reactivity of TPTB 1 on Ag(111) where the formation of a
highly ordered self-assembled structure of aryl radicals was
already observed at room temperature (Fig. S9). At higher
annealing temperatures, only the decomposition of the radicals
generated at the surface was noted.
With biphenyl-4,4'-diyl bis(trifluoromethylsulfonate) BDBT 2 as
the starting material on Cu(111), long linear organometallic chains
were formed at room temperature, resulting from removal of the
trifluoromethyl sulfonyl groups and subsequent deoxygenation of
the aryloxy radicals (Fig. S10). The remaining trifluoromethyl
sulfonyl fragments were located between the chains, enabling via
a template effect the high order and low degree of defects along
the chains. The organometallic chains formed from BDBT 2 on
Cu(111) seem to be very stable, as the structure does not change
upon annealing at 375 K. However, at 440 K the topography
leads to the assumption that some or all triflate groups in this
phase might be split off the backbone.
To study the on-surface reactivity of QDBT 3, we gradually
annealed the sample and observed oligomeric structures along
some individual adsorbates at 400 K (Fig. 3d). CF3SO2-groups
were found to cleave from the monomers and are imaged as
bright protrusions between the oligomeric chains (Fig. 3d). As
only oligomerization products were identified, deoxygenation,
HAT and coupling occurred sequentially at around the same
temperature, unlike for the TPTB 1 case discussed above.
Therefore, aryloxy and aryl radicals could not be identified. In
contrast to TPTB 1, C−C coupling occurred at remote position via
the neighbouring phenyl groups, showing that multiple HAT had
occurred prior to the aryl radical coupling steps. The sub-
molecular resolution image presented in Fig. 3d clearly shows
that the aryl/aryl linkages between the former monomers are
located at the neighbouring phenyl ring, preferably at the meta
positions leading to poly-meta-phenylenes.
Along the remote C–H functionalization events, few ortho
coupling reactions were observed. As the monomeric precursor
can adsorb in two different geometries, linear (L) and kinked (K),
and coupling can occur in ortho (O) and in remote position (R),
four possible reaction sites can be assigned (Fig. 3e top). A
statistical analysis based on 560 C–C bond formations as
obtained from STM images (30 x 30 nm²) revealed that the ratios
of the L-O, L-R, K-O and K-R sites are 4%, 48%, 9% and 39%,
respectively (Fig. 3e). It is currently assumed that stabilization of
the radicals is favoured in remote position as bending of the
molecule along the quaterphenyl backbone leads to a less
distorted structure.
(a)
(b)
1 nm
(c)
Notably, the lower reaction temperature in comparison to TPTB 1
allows the sulfonyl fragments to remain at the surface. Their
template effect enables the preparation of oligomers with a higher
order.[18] Importantly, these sulfonyl fragments can post-
synthetically be removed upon further increasing the temperature
to 440 K (Fig. 3f). During this annealing step, even longer
polymers were obtained and the CF3SO2-fragments probably
decompose into gaseous by-products that leave the surface
under UHV conditions. This is a highly interesting advance over
the well-established Ullmann coupling, where bromine or iodine
adatoms often disturb oligomerization[5] and can stay at the
surface at annealing temperatures up to 540 K.[19]
We further performed lateral manipulation with the STM tip. It
could be demonstrated that the topography of the polymer chain
can be preserved after the tip operation (Fig. 3g and h). This
indicates the strong coupling between the monomeric units and
the phenyl-phenyl distance at the connection points further
supporting the formation of covalent bonds. We also tested
QDBT 3 on Ag(111) surface. Unlike TPTB 1, only weak
interaction between molecules and the substrate was observed
and upon annealing most molecules leave the surface (Fig. S11).
2 nm
1 nm
Figure 2. (a) STM overview image of covalent structures formed after annealing
at 470 K for 20 min. (b-d) High-resolution images and corresponding molecular
models of the proposed product structures. All STM images were acquired with
a tunneling current of I = –0.48 nA and a voltage of Vb = –1.8 V.
changes and unidentified structures were observed. Aryl radical
coupling products or products derived from HAT with subsequent
coupling could not be identified.
We were further interested in the reactivity of an ortho substituted
triflate to understand if ortho coupling is also possible on sterically
more hindered precursors. To this end, ~0.7 ML QDBT 3 was
evaporated onto a Cu(111) surface kept at 300 K (Fig. 3). In the
STM image, formation of two ordered phases, which consist of
linear chains (phase I, Fig. 3b) and paired dimers (phase II,
Fig. 3c), was observed. Due to rotation around the C–C bond
linking the two biphenyl moieties, two distinct adsorption
geometries, imaged as linear or kinked shape, are possible and
self-sorting leads to the two phases. In phase I, molecules
adsorbed with linear geometry self-assembled in chains
composed of both enantiomers arranged alternatingly (Fig. 3b).
Molecules adsorbed in kinked geometry prefer to form head-to-
head dimers in phase II (Fig. 3c). Even though no triflate
fragments were observed and stability of QDBT 3 towards
thermal evaporation was confirmed by in situ EI-MS experiments,
the short distance between the two adsorbates found in phase II
Conclusion
In conclusion we have demonstrated both the self-assembly
behaviour and on-surface reactivity of aryl triflates on Cu(111). In
the case of a sterically less hindered monomer, the formation of
self-assembled structures, organometallic networks and C–H
functionalization was observed. Unlike previous works,[15] where
phenols were found to form phenoxy radicals that undergo phenol
4
This article is protected by copyright. All rights reserved.

10.1002/chem.202002486
Chemistry - A European Journal
FULL PAPER
(a)
(d)
(f)
Phase II
3 nm
Phase I
(g() g)
1 nm
Lateral manipulation
(e)
K-O
K-R
L-O
6 nm
L-R
(b)
50
4 nm
40
30
20
10
0
(h)
1 nm
(c)
L-O
L-R
K-O
K-R
1.5 nm
4 nm
Reaction Position
Figure 3. STM images of QDBT 3 on a Cu(111) at different annealing temperatures, statistical analysis of reaction sites and lateral manipulation. (a) Overview
image of the two coexisting phases I and II acquired with a tunneling current of I = –0.17 nA and a voltage of Vb = –2.1 V after deposition at RT. (b) and (c) High-
resolution images of phase I and II, respectively. Both STM images are acquired with a tunneling current of I = –1.0 nA and a voltage of Vb = –2.1 V. (d) STM
topography after annealing at 400 K acquired with a tunneling current of I = –1.0 nA and a voltage of Vb = –2.7 V. (e) Statistical analysis between ortho (O) and
remote (R) C–H functionalization as well as linear (L) or kinked (K) geometry. (f) STM topography after annealing at 440 K acquired with a tunneling current of
I = –0.3 nA and a voltage of Vb = –2.3 V. (g) and (h) Lateral manipulation of a polymer chain before and after operation. The white arrow in Fig. 3g represents the
movement direction of STM tip during the manipulation. Image tunneling conditions: I = -0.60 nA; Vb = -4.6 V. Manipulation operation conditions: I = –8.0 nA;
Vb = –0.03 V.
coupling in ortho position, the reaction series described above
comprises cleavage of trifluoromethanesulfonyl groups,
deoxygenation, 1,2-HAT and finally C–C coupling, as analysed by
STM after annealing at different temperatures. When one ortho
position is blocked as in QDBT 3, C–C coupling occurred
preferably at a remote C–H position. Trifluoromethanesulfonyl
fragments were found to facilitate templating effects to enable the
preparation of polymers of higher order but can still be removed
applying comparably mild conditions. We are confident that the
triflate group will find further applications in on-surface chemistry
in the future complementing the reactivity of phenols.
Keywords: Aryl triflate • homo coupling • surface chemistry •
STM • self-assembly
[1]
a) P. A. Held, H. Fuchs, A. Studer, Chem. Eur. J. 2017, 23, 5874-5892;
b) T. Wang, J. Zhu, Sur. Sci. Rep. 2019, 74, 97-140; c) S. Clair, D. G. de
Oteyza, Chem. Rev. 2019, 119, 4717-4776; d) L. Grill, S. Hecht, Nat.
Chem. 2020, 12, 115-130.
[2]
a) L. Grill, M. Dyer, L. Lafferentz, M. Persson, M. V. Peters, S. Hecht,
Nat. Nanotechnol. 2007, 2, 687-691; R. Gutzler, H. Walch, G. Eder, S.
Kloft, W. M. Heckl, M. Lackinger, Chem. Commun. 2009, 4456-4458; c)
M. O. Blunt, J. C. Russell, N. R. Champness, P. H. Beton, Chem.
Commun. 2010, 46, 7157-7159.
[3]
[4]
J. Björk, F. Hanke, S. Stafström, J. Am. Chem. Soc. 2013, 135, 5768–
5775.
D. Ebeling, Q. Zhong, T. Schlöder, J. Tschakert, P. Henkel, S. Ahles, L.
Chi, D. Mollenhauer, H. A. Wegner, A. Schirmeisen, ACS Nano 2019, 13,
324-336.
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft (SFB 858, TRR
61) for financial support. H.-Y.G. thanks the NSFC within Grant
21972104 and “1000 Youth Talents Plan”.
[5]
[6]
A. Rastgoo Lahrood, J. Björk, W. M. Heckl, Markus Lackinger, Chem.
Commun. 2015, 51, 13301-13304.
M. Lischka, M. Fritton, J. Eichhorn, V. S. Vyas, T. Strunskus, B. V. Lotsch,
J. Björk, W. M. Heckl, M. Lackinger, J. Phys. Chem. C 2018, 122, 5967-
5977.
5
This article is protected by copyright. All rights reserved.

10.1002/chem.202002486
Chemistry - A European Journal
FULL PAPER
[7]
[8]
[9]
D. Barton, H.-Y. Gao, P. A. Held, A. Studer, H. Fuchs, N. L. Doltsinis, J.
Neugebauer, Chem. Eur. J. 2017, 23, 6190-6197.
S. Zint, D. Ebeling, T. Schlöder, S. Ahles, D. Mollenhauer, H. A. Wegner,
A. Schirmeisen, ACS Nano 2017, 11, 4183-4190.
H.‐Y. Gao, P. A. Held, M. Knor, C. Mück‐Lichtenfeld, J. Neugebauer, A.
Studer, H. Fuchs, J. Am. Chem. Soc. 2014, 136, 9658-9663.
[10] J. Liu, Q. Chen, Q. He, Y. Zhang, X. Fu, Y. Wang, D. Zhao, W. Chen, G.
Q. Xu, K. Wu, Phys. Chem. Chem. Phys. 2018, 20, 11081-11088.
[11] A. Riss, A. P. Paz, S. Wickenburg, H.-Z. Tsai, D. G. De Oteyza, A. J.
Bradley, M. M. Ugeda, P. Gorman, H. S. Jung, M. F. Crommie, A. Rubio,
F. R. Fischer, Nat. Chem. 2016, 8, 678-683.
[12] L. Liu, H. Klaasen, A. Timmer, H.-Y. Gao, D. Barton, H. Mönig, J.
Neugebauer, H. Fuchs, A. Studer J. Am. Chem. Soc. 2018, 140, 6000-
6005.
[13] a) Q. Sun, L. Cai, Y. Ding, H. Ma, C. Yuan and W. Xu, Phys. Chem.
Chem. Phys. 2016, 18, 2730-2735; b) Q. Sun, L. Cai, H. Ma, C. Yua, W.
Xu, Chem. Commun. 2016, 52, 6009-6012; c) Q. Sun, L. Cai, H. Ma, C.
Yuan, W. Xu, ACS Nano 2016, 10, 7023-7030; d) M. Liu, S. Li, J. Zhou,
Z. Zha, J. Pan, X. Li, J. Zhang, Z. Liu, Y. Li, X. Qiu, ACS Nano 2018, 12,
12612-12618.
[14] a) K. J. Shi, X. Zhang, C. H. Shu, D. Y. Li, X. Y. Wu, P. N. Liu, Chem.
Commun. 2016, 52, 8726-8729; b) K. J. Shi, D. W. Yuan, C. X. Wang, C.
H. Shu, D. Y. Li, Z. L. Shi, X. Y. Wu, P. N. Liu, Org. Lett. 2016, 18, 1282-
1285.
[15] a) Q. Li, B. Yang, H. Lin, N. Aghdassi, K. Miao, J. Zhang, H. Zhang, Y.
Li, S. Duhm, J. Fan, L. Chi, J. Am. Chem. Soc. 2016, 138, 2809-2814; b)
B. Yang, N. Cao, H. Ju, H. Lin, Y. Li, H. Ding, J. Ding, J. Zhang, C. Peng,
H. Zhang, J. Zhu, Q. Li, L. Chi, J. Am. Chem. Soc. 2019, 141, 168-174.
[16] J. Ren, E. Larkin, C. Delaney, Y. Song, X. Jin, S. Amirjalayer, A. Bakker,
S. Du, H. Gao, Y.-Y. Zhang, S. M. Draper, H. Fuchs, Chem. Commun.
2018, 54, 9305-9308.
[17] Q. Fan, S. Werner, J. Tschakert, D. Ebeling, A. Schirmeisen, G. Hilt, W.
Hieringer, J. M. Gottfried, J. Am. Chem. Soc. 2018, 140, 7526-7532.
[18] J. Ren, M. Cnudde, D. Brunink, S. Buss, C. G. Daniliuc, L. Liu, H. Fuchs,
C. A. Strassert, H.-Y. Gao, N. L. Doltsinis, Angew. Chem. 2019 131,
15542-15546; Angew. Chem. Int. Ed. 2019, 58, 15396-15400.
[19] C. Bronner, J. Björk, P. Tegeder, J. Phys. Chem. C 2015, 119, 486-493.
6
This article is protected by copyright. All rights reserved.

10.1002/chem.202002486
Chemistry - A European Journal
FULL PAPER
Entry for the Table of Contents
Insert graphic for Table of Contents here.
Insert text for Table of Contents here. Step aside! Coupling of aryl triflates, so far unknown in on-surface chemistry, is reported.
Unlike aryl halides known in Ullmann coupling, aryl radicals formed from triflated monomers undergo HAT prior to C–C coupling,
leading to unexpected regioselectivity. But not only H-atoms step aside: triflate fragments show a powerful templating effect during
the reaction and leave the surface post-synthetically under mild conditions.
7
This article is protected by copyright. All rights reserved.