Influence of a Metal Substrate on Small-Molecule Activation Mediated by a Surface-Adsorbed Complex

Article abstract of DOI:10.1002/chem.201800911

Activating small molecules with transition metal complexes adsorbed on metal surfaces is a novel approach combining aspects of homogeneous and heterogeneous catalysis. In order to study the influence of an Au(111) substrate on the activation of the small-molecule ligand carbon monoxide, a molybdenum tricarbonyl complex containing a PN³P pincer ligand was synthesized and investigated in the bulk, in solution, and adsorbed on an Au(111) surface. By means of a platform approach, a perpendicular orientation of the molybdenum complex was achieved and confirmed by IRRAS and NEXAFS. By using vibrational spectroscopy (IR, Raman, IRRAS) coupled to DFT calculations, the influence of the metal substrate on the activation of the CO ligands bound to the molybdenum complex was determined. The electron-withdrawing behavior of gold causes an overall shift of the CO stretching vibrations to higher frequencies, which is partly compensated by dynamic charge transfer from the substrate to the molybdenum center, which increases its (dynamic) polarizability.

Full text of DOI:10.1002/chem.201800911

A Journal of
Accepted Article
Title: Influence of a Metallic Substrate on the Small Molecule Activation
Mediated by a Surface Adsorbed Complex
Authors: Alexander Schlimm, Nadja Stucke, Benedikt Maria Flöser,
Talina Rusch, Jan Krahmer, Thomas Strunskus, Christian
Näther, Olaf Magnussen, and Felix Tuczek
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.201800911
Link to VoR: http://dx.doi.org/10.1002/chem.201800911
Supported by

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
Influence of a Metallic Substrate on the Small Molecule Activation
Mediated by a Surface Adsorbed Complex
Alexander Schlimm#[a], Nadja Stucke#[a], Benedikt M. Flöser[a], Talina Rusch[b], Jan Krahmer[a], Christian
Näther[a], Thomas Strunskus[c], Olaf M. Magnussen[b], Felix Tuczek*[a]
Dedicated to Professor Bernt Krebs on the occasion of his 80th anniversary
Abstract: Activating small molecules with transition metal complexes
adsorbed on metallic surfaces is a novel approach combining aspects
of homogeneous and heterogeneous catalysis. In order to study the
influence of an Au(111) substrate on the activation of the small
molecule ligand carbon monoxide a molybdenum triscarbonyl com-
plex containing a PN3P pincer ligand is synthesized and investigated
in the bulk, in solution and adsorbed on an Au(111) surface. Via a
platform approach a perpendicular orientation of the molybdenum
complex is achieved and confirmed by IRRAS and NEXAFS. Using
Figure 2: Design of the new [Mo(CO)3(Me-PN3PTATA)] (1) complex and
vibrational spectroscopy (IR, Raman, IRRAS) coupled to DFT
formation of a monolayer of 1 on Au(111).
calculations the influence of the metallic substrate on the activation of
involve the simultaneous transfer of electrons and protons to or
the CO ligands bound to the molybdenum complex is determined. The
from the activated substrate. Important examples for such
electron withdrawing behavior of gold causes an overall shift of the
reactions are hydrogen evolution (HER), oxygen evolution during
CO stretching vibrations to higher frequencies, which is partly
water splitting (OER), oxygen reduction (ORR) or reduction of
compensated by a dynamic charge transfer from the substrate to the
CO2. A particular challenging case is nitrogen fixation as it
molybdenum center, increasing its (dynamic) polarizability.
involves protonation and reduction of the most inert molecule of
the universe, N2.[9] Inspired by the biological process of nitrogen
fixation,[10] a number of molybdenum, iron and other transition
metal complexes have been synthesized which catalyze the
Introduction
conversion of N2 to NH3 in homogeneous solution.[2,3,5,11–20]
Besides proton donors like HBArF (BArF = tetrakis[3,5-
Many important reactions in industry, biology or energy
4
4
bis(trifluoromethyl)-phenyl]borate) or lutidinium salts these
processes require the addition of reducing agents; e.g.,
decamethylchromocene or KC8.[2,11,12,15]
conversion are based on the activation of small molecules by
transition metal complexes.[1–8] Often these processes also
In the past years, significant effort has been directed
towards the attachment of catalysts active in HER, OER or ORR
to metallic or semiconducting electrodes with the goal of
performing the processes in an electrocatalytic fashion.[21]
Moreover, the functionalized electrodes were studied with
electrochemistry and surface spectroscopy in order to obtain
mechanistic information on the investigated reactions. Regarding
nitrogen fixation, attachment of the FeMoco of nitrogenase to a
cathode with the goal of electrocatalytically synthesizing NH3 from
N2 has been reported.[22] Similar studies with synthetic transition
metal complexes binding and activating N2 are, however,
scarce.[23–25] Nevertheless, attachment of dinitrogen complexes to
metallic surfaces could provide significant advantages; i.e., it may
lower the activation energy required for the conversion of N2 to
ammonia in a sequence of protonation and reduction steps.
Moreover, it might enable alternative pathways, e.g., the reaction
of N2 with H2 under ambient conditions.[26,27]
In the literature a number of strategies to fix transition metal
complexes (often porphyrins or related systems) to surfaces have
been described (fig. 1).[28] In the most direct fashion, the molecule
is physisorbed to the surface by deposition from solution or, after
evaporation of the bulk material, from the gas phase (fig. 1a).[29,30]
This approach potentially entails some problems. Firstly, due to
the direct contact between the metal complex and the surface
some complexes may decompose.[31] Depending on the nature of
Figure 1: Different deposition methods of transition metal complexes on
surfaces: a) physisorption (direct deposition), b) chemisorption via a functional
group (e.g. thiols).
# The authors contributed equally to this paper.
[a]
A. Schlimm, N. Stucke, B. M. Flöser, J. Krahmer, Prof. Dr. C.
Näther, Prof. Dr. F. Tuczek*
Institute of Inorganic Chemistry
Christian Albrechts University Kiel
Max-Eyth-Str. 2, 24118 Kiel
E-mail: ftuczek@ac.uni-kiel.de
[b]
[c]
T. Rusch, Prof. Dr. O. M. Magnussen
Institute of Experimental and Applied Physics
Christian Albrechts University Kiel
Leibnizstr. 19, 24118 Kiel
Dr. T. Strunskus
Institute for Materials Science – Multicomponent Materials
Christian Albrechts University Kiel
Kaiserstr. 2, 24143 Kiel
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
Scheme 1: Synthesis of the tridentate pincer ligand Me-PN3PTMS (2).
the complex, the interaction between the surface and the metal
complex may be weak or sensitive to changes in its electronic and
geometric structure.[32–34] In the case of porphyrins, e.g., the
interaction of the complex with the surface is reduced upon
binding of a ligand trans to the surface.[33] This is avoided if the
molecules are covalently attached to the surface, e.g. by a thiol
function to Au(111) (fig. 1b).[35,36] In this case, however, the
orientation of the complex with respect to the surface is less
defined. The complex may also be “clicked” to a self-assembled
monolayer (SAM) which has been deposited first onto the metal
surface.[24,37–40] The aliphatic spacer groups thereby lead a large
separation between the surface and the head group.
Consequently, the electronic influence of the metallic substrate is
distinctly decreased compared to the direct deposition.[40]
[Mo(CO)3(Me-PN3PTATA)] complex (1) is investigated in the solid
state, in solution and adsorbed on a gold(111) surface using a
range of spectroscopic and analytical methods. The electronic
effect of the metallic substrate on the molybdenum carbonyl
complex is evaluated, and the implications on the reactivity of
small-molecule ligands bound to surface-adsorbed transition
metal complexes are considered.
Results and Discussion
Synthesis and characterization of [Mo(CO)3Me-
PN3PTATA] (1) in solution and the bulk
Synthesis of the PN3P ligand and [Mo(CO)3(Me-PN3PTMS)] (3)
Another useful and elegant approach to surface attachment
is
based
on
platform
molecules.[41–48]
The
TATA
It has been shown in previous studies by HAUPT et al.[54] and
K
(triazatriangulenium) platform, developed by LAURSEN et al.[49]
,
IRCHNER et al.[55] that PN3P ligands can coordinate in a
allows the fixation and orientation of functional molecules on a
metallic substrate. The adsorbed molecules thereby form highly
ordered monolayers.[41] The advantage of the TATA platform
compared to the thiol concept is the increased lateral distance
between the surface-adsorbed molecules, suppressing
intermolecular interactions which may affect the functionality of
the molecule.[50] Furthermore, the coupling unit between the
platform and the metal complex can be modified in order to tune
the interaction between the metallic substrate and the
complex.[42,51] Finally, the molecule attached to the platform is
strictly perpendicular to the surface, rendering this concept
amenable to the application of Infrared-Reflection-Absorption-
Spectroscopy (IRRAS) in order to obtain electronic and structural
information.[52,53]
meridional fashion to metal centers via two phosphine donors and
the pyridine unit. In order to couple the PN3P ligand to the TATA
platform the central pyridine ring has been functionalized in 4-
position with a trimethylsilyl-protected acetylene moiety. The
corresponding Me-PN3PTMS ligand (2) was obtained by the
synthetic route shown in Scheme 1. Metalation of 2 afforded the
Mo(0) carbonyl complex [Mo(CO)3(Me-PN3PTMS)] (3), which in
turn was connected with the TATA platform, leading to the target
complex 1 (see below, Scheme 2).
In order to elucidate the influence of a metallic substrate on
the electronic structure of surface-adsorbed transition metal
complexes activating small-molecule ligands like N2 or CO, we
herein investigate
a molybdenum(0) triscarbonyl complex
supported by a tridentate PN3P pincer ligand which is linked via
an alkyne spacer to a TATA platform, allowing its deposition to
metallic surfaces (fig. 2). Compared to complexes of the
isoelectronic dinitrogen ligand, carbonyl complexes are more
stable. Furthermore, C-O stretches exhibit high IR-activities and
are therefore well suited for investigations using surface
vibrational spectroscopy. The new TATA-functionalized
Scheme 2: Synthesis of [Mo(CO)3(Me-PN3PTMS)] (3) and [Mo(CO)3(Me-
PN3PTATA)] (1).
For the synthesis of ligand 2 the hydroxyl group in 4-position
of chelidamic acid was first substituted by bromide using PBr5
(Scheme 1). In the course of this reaction the carboxylic acid
groups were esterified yielding the diethyl ester 4.[56] Employing
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
hydrazine hydrate the dihydrazide 5 was generated which was
subsequently converted into the diazide.[56] Via a CURTIUS
rearrangement and the addition of tert-butanol the dicarbamate 6
was obtained.[56] As a next step the dicarbamate 6 were
deprotonated by sodium hydride and methylated using
iodomethane. The TMS-protected ethynyl group was introduced
by a Sonogashira cross coupling. Due to the lability of the TMS
unit towards acids the Boc protecting group was cleaved by ZnBr2
in dichloromethane.[57] Finally, the diphenylphosphine groups
were introduced with chlorodiphenyl-phosphine in the presence of
n-BuLi.[58]
backbonding. As a consequence π backbonding between
molybdenum and the axial carbonyl ligand (C32) is increased,
causing a shortening of the Mo-C32 bond (1.968 Å) compared to
the bond lengths between molybdenum and the equatorial
carbonyl ligands (≈ 2.023 Å). In spite of these electronic
differences the C-O distances within the carbonyl ligands differ
only slightly: whereas the Ceq-Oeq bond lengths are 1.145 Å (C31-
O1) and the Cax-Oax bond length is 1.144 Å. Due to the methyl
residues at the amine N atoms the rotation of the phenyl rings is
sterically restricted. As a result the Mo(CO)3(PPh2) fragment (fig.
3, right) exhibits C2 symmetry (vide supra).
Crystal structure of [Mo(CO)3(Me-PN3PTMS)] (3)
Synthesis of [Mo(CO)3(Me-PN3PTATA)] (1)
Reaction of ligand 2 with the precursor [Mo(CO)3(CH3CN)3]
afforded the Mo(0) carbonyl complex [Mo(CO)3(Me-PN3PTMS)] (3).
Crystals of 3·2 CH3CN suitable for single crystal X-ray
determination were obtained by slow evaporation of the solvent
(acetonitrile). The structure of 3 is shown in figure 3.
The key step in the synthesis of the target molecule was the
coupling between the alkyne function and TATA platform. A
common strategy to functionalize the TATA unit is the reaction of
an unprotected, anionic ethynyl residue with the cationic
platform.[59] The alkyne functionality serves as linker between the
TATA molecule and the desired functional unit (in our case the
metal complex). We started our investigation using the related
ligand H-PN3PTMS which has protons instead of methyl residues
at the amine units. First attempts to couple this ligand to “octyl-
TATA” (i.e., a TATA platform with octyl substituents)[41] were
unsuccessful. This negative result most probably is due to the
protons at the secondary amine units. In the presence of an
excess of KOH (which is necessary to eliminate the TMS
protecting group) the secondary amine groups may become
deprotonated. To prevent this side reaction we introduced methyl
groups into the PN3PTMS ligand.[58] However, attempts to couple
this ligand to the TATA platform using KOH failed as well. Using
NMR spectroscopy we determined that potassium hydroxide
cleaves the N-P bond instead of exclusively eliminating the
protecting group. To ensure that the ligand remains intact during
the reaction we decided to coordinate the ligand first to the
molybdenum carbonyl precursor and connect the complex to the
octyl-TATA platform afterwards. In this way, the phosphine units
are protected by coordination to the molybdenum center.[60] An
additional advantage of this approach is the fact that it avoids a
metalation of surface-deposited ligands which may be associated
with further problems. Following this strategy, the TMS protecting
Figure 3: Crystal structure of [Mo(CO)3(Me-PN3PTMS)] (3) (left: side view) right:
top view).
Selected bond distances and angles are collected in table
1. The complex 3 is located on a 2-fold rotation axis. The
molybdenum center is coordinated in a distorted octahedral
fashion by the Me-PN3PTMS pincer ligand (2) and the three
carbonyl groups. The P1-Mo-P1A angle amounts to 156.4 °and
is distinctly smaller than 180 °. Conversely, the t wo equatorial CO
ligands are inclined towards the axial carbonyl ligand; i.e., the
C31-Mo-C31A angle (169.1 °) is also reduced from 18 0 °. The
experimental bond lengths reflect the bonding properties of the
donor atoms obtained from DFT (SI, fig. S 14). The Mo-N bond
(2.240 Å) between the metal center and the pyridine N is
elongated compared to related Mo-PNP compounds in the
literature (2.182 Å).[2] This goes along with a loss of π-
Table 1. Selected bond lengths [Å] and angles [°] of [Mo(CO )3(Me-
PN3PTMS)] (3)
Mo(1)-C(32)
Mo(1)-C(31)
Mo(1)-C(31A)
Mo(1)-N(1)
Mo(1)-P(1)
Mo(1)-P(1A)
O(1)-C(31)
O(1A)-C(31A)
O(2)-C(32)
1.968(3)
2.023(2)
2.023(2)
2.2400(19)
2.3750(5)
2.3750(5)
1.145(3)
1.145(3)
1.144(4)
C(32)-Mo(1)-P(1)
C(32)-Mo(1)-P(1A)
C(C31A)-Mo(1)-P(1)
C(31A)-Mo(1)-P(1A)
C(31)-Mo(1)-P(1)
C(31)-Mo(1)-P(1A)
C(32)-Mo(1)-N(1)
C(31)-Mo(1)-N(1)
C(31A)-Mo(1)-N(1)
N(1)-Mo(1)-P(1)
101.809(12)
101.809(12)
93.71(6)
88.52(6)
88.52(6)
93.71(6)
180.0
95.44(6)
95.44(6)
78.191(12)
78.191(12)
156.38(2)
N(1)-Mo(1)-P(1A)
P(1)-Mo(1)-P(1A)
C(32)-Mo(1)-C(31)
C(32)-Mo(1)-C(31A)
C(31)-Mo(1)-C(31A)
84.56(6)
84.56(6)
169.11(12)
Figure 4: 13C-NMR spectrum of [Mo(CO)3(Me-PN3PTATA)] (1) measured in
toluene-d8. The resonances of the carbonyl C’s are enlarged.
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
group could easily be removed in situ within one hour using KOH
without a decomposition of the complex or ligand, respectively.
After the addition of octyl-TATA*BF4 the reaction mixture was
stirred for another 75 min. The target compound could be
obtained after purification via column chromatography using basic
alumina under air. The same reaction using the complex
[Mo(CO)3(H-PN3PTMS)] (crystal structure is shown in fig. S 13) and
the octyl-TATA platform failed. This result underscores the
necessity of the methyl substituents at the amine groups.
associated with the stretching vibration of the alkyne group that is
IR-inactive.
The new complex [Mo(CO)3(Me-PN3PTATA)] (1) was first
investigated in the bulk and in solution. The 13C-NMR spectrum of
1 is shown in figure 4. Using DEPT-135 and 2D correlation NMR
techniques all resonances could be located and assigned to the
respective carbon atoms. In particular, the meridional
coordination geometry around the Mo(0) center is supported by
13C-NMR spectroscopy. The axial CO (red, fig. 4) exhibits a signal
at 226.2 ppm and gives rise to a triplet with a coupling constant of
5 Hz due to a coupling to the equivalent 31P nuclei. The signal of
the equatorial COs is located at 211.0 ppm and is split as well into
a triplet with a coupling constant of 9.9 Hz. The molybdenum
mediated coupling between the equatorial 13COs and the 31P
nuclei is twice as large as the coupling between the axial 13CO
and the phosphorus atoms because of a better overlap of the Mo-
d-orbitals and the orbitals of the CO and PPh2 units in the
equatorial plane.[61] In contrast, the 13C-31P coupling could not be
observed in the 31P-NMR spectrum. Consequently, the two
phosphorus nuclei give rise to a singlet at 133.0 ppm.
Figure 5: Left: IR und Raman spectra of [Mo(CO)3(Me-PN3PTATA)] (1). Right:
Illustration of the observed CO vibrations. The Raman data were multiplied with
the factor 15.
Deposition and characterization of monolayers of
[Mo(CO)3Me-N3PTATA]@Au(111)
After synthesizing the novel molybdenum(0) complex containing
the Me-PN3P ligand (2), connecting the [Mo(CO)3(Me-PN3PTMS)]
complex (3) to the octyl-TATA platform and characterizing the
resulting complex 1 in solution and the bulk, 1 was deposited on
Au(111). The resulting monolayer was investigated using a range
of surface-spectroscopic and -analytical methods.
Complex 1 was further investigated by infrared and Raman
spectroscopy. Vibrational spectroscopy is particularly useful to
monitor the activation of small molecules coordinated to transition
metal centers. The IR (top) and Raman (bottom) spectra of 1 are
shown in figure 5. The first coordination sphere of the
molybdenum center comprises the three CO ligands, two
phosphorus atoms and one pyridine nitrogen. The phenyl rings of
the phosphine units can rotate freely at room temperature;
therefore, the complex exhibits effective C2v symmetry. As
expected for this point group, three carbonyl bands are observed
in the IR spectrum. The totally symmetric A1(1) vibration, in which
all three carbonyl ligands oscillate in phase, is located at
1964 cm-1 (fig. 5, blue) in the IR and Raman spectrum. A second
A1 vibration (A1(2)), located at 1840 cm-1, (fig. 5, green), is the out-
of-phase combination of a symmetric stretch of the equatorial CO
ligands and the stretch of the axial CO ligand. The intensity in the
Raman spectrum is weak compared to the signal of the A1(1)
vibration. Furthermore, this signal is broadened due to overlap
with the B1 vibration. The two vibration bands can be resolved in
the IR with the A1(2) and the B1 modes being located at 1840 and
1862 cm-1, respectively (fig. 5, green and red). The latter vibration
is characterized by the antisymmetric stretching motion of the
equatorial CO ligands. Although the A1(2) and B1 vibrations are
group-theoretically Raman-allowed, their Raman intensity is weak
since, due to their antisymmetric character, there is no change in
polarizability along the respective vibrational coordinate. Taken
together, the results of vibrational spectroscopy indicate an
activation of the carbonyl ligands compared to free carbon
monoxide (2143 cm-1).[62] The intense peak in the Raman
spectrum at 1589 cm-1 is assigned to a symmetric C-C stretching
vibration of the pyridine ring whereas the peak at 2205 cm-1 is
STM measurements of [Mo(CO)3Me-PN3PTATA]@Au(111)
Scanning Tunneling Microscopy (STM) was employed to image
the in-plane arrangement of the molecular adsorbates on Au(111)
surfaces. In particular, the long-range order and intermolecular
distances within monolayers of surface-adsorbed molecules were
determined.[50,63] Previous studies revealed that inert gold
substrates are well suited for the deposition of TATA
derivatives.[42,43] Following the procedures in these studies,
monolayers of [Mo(CO)3(Me-PN3PTATA)] (1) were prepared by
immersing an Au(111) substrate in a toluene solution of 1 for 5-
10 minutes.
Figure 6: STM image (35 x 35) nm² of [Mo(CO)3(Me-PN3PTATA)] (1) adlayer on
Au(111). The pink spheres (right) represent the octyl chains of the TATA
platform.
Investigation of the adsorbed [Mo(CO)3(Me-PN3PTATA)] (1)
revealed highly ordered hexagonal monolayers on the Au(111)
surface (fig. 6). The measured lattice constant of 1.25 (± 0.05) nm
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
and the angles between the rotational domains are in good
agreement with previous STM results of different octyl-TATA
nitrogen atom of the pyridine. At lower energy, 398.7 eV (red
trace), a signal of the amine nitrogen atoms of the Me-PN3P ligand
moiety can be observed. Again, the ratio of the relative intensities
(50:33:17) conforms to the values (50:33:17) calculated from the
elemental composition.
The Mo 3d spectrum (fig. 7d) contains only one doublet at
227.4 eV and 230.5 eV with a characteristic splitting of 3.1 eV
(38:62). Such binding energies are typical for Mo(0) complexes
with phosphine ligands.[65] Another doublet is found in the P 2p
spectrum (fig. 7e) at 132.8 eV and 131.5 eV with the typical
splitting of 1.3 eV (65:35). This signal corresponds to the
phosphine species of the Me-PN3P-pincer ligand. In conclusion,
the XP-spectra confirm the presence of a monolayer of the
[Mo(CO)3(Me-PN3PTATA)] complex (1) in high purity and without
any oxidized species.
derivatives and correspond to a commensurate ( √19× √19 )
R23.4° superstructure. [50] The intermolecular distance of 1.25 ±
0.05 nm and hexagonal superstructure thus indicate that the octyl
side chains dominate the organization process on surface. Thus,
in contrast to other TATA derivatives with sterically demanding
central substituents, the phenyl units of the attached molybdenum
complex have no influence on the lateral organization of the
functionalized TATA molecules on the surface.[59]
XPS measurements of [Mo(CO)3Me-PN3PTATA]@Au(111)
In order to check whether the [Mo(CO)3(Me-PN3PTATA)] complex
(1) was deposited intactly and without contaminations on Au(111)
X-ray photoelectron spectroscopy (XPS) was employed. The
resulting XP spectra are given in figure 7. The major signals
shown in the survey spectrum (fig. 7a) are the Au 4f lines at 84.0
eV and 87.5 eV. Furthermore, the Au 3d signals at 335.0 eV and
352.5 eV are clearly visible as well as the C 1s peak at 284.5 eV.
Based on the survey spectrum the N 1s signal is identified at 399
eV.
To determine the binding energies of the different species
located in the N 1s, P 2p and Mo 3d signals, high resolution
spectra of the different regions with acquisition times up to one
hour were measured. The C 1s spectrum (fig 7b) contains three
signals. The most prominent signal at 284.7 eV (blue trace)
reflects the aliphatic and aromatic carbon atoms connected
among each other. A smaller signal at 285.5 eV (red trace) can
be assigned to the carbon atoms which are bonded either to
nitrogen or phosphorus atoms. The third species (green trace)
corresponds to the C atoms of the C-O ligands.[64] Importantly, the
ratio of the relative intensities (74:23:3) fits to the values derived
from the molecular composition (74:22:4). Considering the high
resolution N 1s spectrum (fig 7c) three species can be located in
the main signal. The one with the highest intensity (blue trace) at
399.6 eV can be assigned to nitrogen atoms directly connected to
carbon atoms representing the nitrogen atoms of the TATA
platform. The signal at 400.4 eV (green trace) refers to the
NEXAFS measurements of [Mo(CO)3(Me-PN3PTATA)]@ Au-
(111)
NEXAFS spectra were measured at the carbon and nitrogen K-
edges for monolayers of [Mo(CO)3(Me-PN3PTATA)] (1) on Au(111)
single crystals. The C K-edge spectrum, shown in figure 8a,
exhibits two π* resonances which can be found in the spectrum
derived from DFT (fig. 8, bottom) as well. Using this calculation
the first resonance at 285.4 eV is assigned to a C 1s to π*
transition of the phenyl groups and the pyridine moiety of the Me-
PN3P ligand backbone. It is literature-known that pyridine (285.6
eV) and alkyne (286.0 eV) carbons give rise to a resonance at
these energies.[66,67] The contribution of the pyridine and alkyne
unit to this resonance is distinctly smaller than the contribution of
the PPh2 carbons. Consequently, the small shoulder at 285.9 eV
is assigned to the pyridine and alkyne carbons. This also accounts
for the missing angular dependence, as the phenyl groups of the
ligand are freely rotatable and show no preferred orientation. The
calculations show that the CO ligands also have a small
contribution to this resonance at 285.4 eV. The second π*
resonance located at 289.1 eV contains transitions of the Me-
PN3P ligand and the TATA platform. At higher binding energies
(293.6 eV) the C 1s-to-σ* transitions can be observed. The N K-
edge NEXAFS spectrum (fig. 8b) shows three resonances. Based
on the DFT calculations and former studies on TATA systems the
π* resonance at 402.4 eV are assigned to the N 1s–to-LUMO
transition of the TATA nitrogen atoms.[68] Importantly, this
resonance exhibits a significant angular dependence with
Figure 8: Normalized NEXAFS spectra of a monolayer of [Mo(CO)3(Me-
PN3PTATA)] (1) on Au(111) at different angles (30°, 55°, 70°, 90°) and the
calculated NEXAFS data (shifted by +10.7 eV (C) and +12.6 eV (N)) with
the contributions of the different subunits summarized over all angles: a) C
K-edge spectrum; b) N K-edge spectrum.
Figure 7:Survey (a), C 1s (b), N 1s (c), Mo 3d (d) and P 2p (e) XP spectra of a
monolayer of [Mo(CO)3(Me-PN3PTATA)] (1) on Au(111).
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
vanishing intensity at 90°. This result confirms th e parallel
orientation of the TATA platform to the surface and has also been
observed in previous investigations.[50] The π* resonance at 401.2
eV is of low intensity and corresponds to the amines of the ligand
backbone. The intense π* resonance at 399.1 eV corresponds to
the pyridine nitrogen atom. Suprisingly, it only exhibits a a very
weak angular dependence. This transition was therefore
investigated in more detail using DFT. As can be seen in figure 9
the target orbitals of the dominant transitions involving this atom
are close in energy and strongly delocalized over the
molybdenum center and the ligands. The angular dependence of
the pyridine π* resonance thus almost disappears. In conclusion,
the measured NEXAFS spectra can be well understood with the
help of DFT calculations.
Figure 10: Computed and measured vibrational spectra of [Mo(CO)3(Me-
PN3PTATA)] (1) in bulk material and adsorbed on Au(111).
better signal-to-noise ratio the surface IR spectrum of 1@Au(111)
was measured using PM-IRRAS. Thus the signals in the
fingerprint region are also better resolved. The absorption band at
1087 cm-1 in the IRRA spectrum is associated with C-H
deformation vibrations of the octyl side chains. In the IRRA
spectrum, this vibrational mode shows a higher relative intensity
than in the bulk IR spectrum because of the free mobility of the
side chains although the molecule is adsorbed on the surface. In
the region between 1400 cm-1 and 1530 cm-1 different aromatic
(TATA platform), aliphatic C-H rocking and bending vibrations are
located. These vibrations are of low intensity in the IRRA
spectrum as the transition dipole moments are mostly parallel to
the surface. The aromatic deformation vibrations of the phosphine
phenyl groups correspond to the band at 1587 cm-1 in the IRRA
spectrum. This absorption band shows a high relative intensity
due to the fact that the phenyl units can rotate freely. For this
reason there are different conformers with transition dipole
moments of the respective vibration perpendicular to the surface.
In the region of the carbonyl stretching vibrations three
bands of the CO ligands of 1 can be detected in the bulk IR
spectrum (vide supra). The A1(1) mode at 1964 cm-1 shows a
higher relative intensity in the IRRA spectrum than in the bulk IR
as the transition dipole moment of this vibration is exactly
perpendicular to the surface. This behavior is also shown in the
calculated IR and IRRA spectra. The B1 vibration is located at
1862 cm-1 in the bulk IR spectrum. The transition dipole moment
of this vibration mode is nearly parallel to the surface. Therefore,
the relative intensity of this mode in the IRRA spectrum (1893
cm-1) is drastically decreased in comparison to the bulk IR. The
A1(2) vibration, finally, is observed at 1876 cm-1 in the IRRA
spectrum. The obtained relative intensity in the IRRA spectrum is
higher than in the bulk IR spectrum. Thus, the transition dipole
moment of this mode is perpendicular to the surface.
Consequently, the perpendicular orientation of the metal complex
1 with respect to the surface is proven. However, the frequency
difference of the B1/A1(2)-CO stretches is significantly smaller in
the IR spectrum calculated for 1. Consequently, only one band
appears in the simulation (fig. 10). Nevertheless, the detailed
vibrational analysis (Table S 7.) reveals that both vibrational
modes are present in the calculated spectra. The frequencies of
Figure 9: Contour plots of the LUMO, LUMO+1, LUMO+3, LUMO+6 of
[Mo(CO)3(Me-PN3PTATA)] (1) with orbital energies given as differences to
the LUMO.
IRRAS measurements of [Mo(CO)3Me-PN3PTATA]@Au(111)
Besides the commonly applied surface spectroscopic methods
STM, XPS and NEXAFS, IRRA spectroscopy was employed to
investigate [Mo(CO)3(Me-PN3PTATA)] adsorbed on gold
(1@Au(111)). Intensities of around 10-3 absorbance units reflect
the formation of a monolayer on Au(111) (fig. 10).[52] To determine
the influence of the gold substrate on the activation of the carbonyl
ligands the measured IRRA spectrum was compared to bulk and
computed IR spectra. The calculated bulk and IRRA spectra look
very similar to the measured IR spectra (fig. 10). Consequently,
the bands appearing in the measured spectra could be assigned
to specific vibrational modes. Note that differences in relative
intensities of the bands in the bulk IR and IRRA spectra are
caused by the surface-selection-rule of IRRAS.[53] In this way,
precise information about the orientation of molecules to the
surface are accessible. Thereby it is of great advantage that the
carbonyl ligands of 1 exhibit intense IR bands. Because of the
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
the carbonyl stretching vibrations in the free and the surface-
adsorbed complex 1 are collected in table 2.
eigenvalues suffer from basis set superposition errors (BSSE).
For ∆E this was corrected with a counterpoise correction which
unfortunately was not possible for the ∆Eorb contribution.
Nonetheless, the leading pair of eigenvectors can be depicted as
deformation density as in figure 11 and showcases the regions of
electron accumulation and depletion upon interaction of the
fragments. It can be seen that the net electron density on (1) is
decreased notably on the Mo center and its vicinity whereas the
electron density on the gold surface increases in a delocalized
fashion. The majority of the deformation density, however, mostly
shows electron depletion on the TATA platform (not shown here).
This is consistent with the computed partial charges listed in table
3 which indicate that charge transfer predominantly occurs
between the platform and the surface. Nonetheless it should be
noted that a non-negligible amount of charge is taken from the Mo
atom under participation of metal d-orbitals as is shown by the
NOCV analysis. This indicates electronic coupling between the
gold surface and the Mo central atom and accounts for the
electronic and vibrational structure changes observed upon
surface adsorption of complex 1.
Table 2. Comparison of the CO absorption bands in IRRAS and Bulk IR.
Band
Bulk IR/cm-1
IRRAS/cm-1 Shift cm-1
A1(1)
B1
A1(2)
1964
1862
1840
1972
1893
1876
8
31
36
In order to account for the observed frequency shifts of the
CO vibrations a possible transfer of electronic charge between the
gold substrate and adsorbed metal complex has to be considered.
A few examples in literature reveal an electron donating behavior
from the gold towards the deposited transition metal
complex.[32,33,69] The opposite effect, corresponding to an electron
withdrawing behavior of the gold substrate, would lead to a
decreased electron density at the adsorbed molecules. The
results of the vibrational spectroscopic investigations in the
present study in fact indicate an electron withdrawing behavior of
the gold as the CO stretching frequencies of the adsorbed
complex shift to higher energies.
The electron withdrawing character of the gold substrate
with respect to a Mo(0) carbonyl complex can be reproduced by
DFT considering Löwdin partial charges; the results are collected
in table 3. As evident from the bottom line of table 3, 1.64 charge
units are transferred from [Mo(CO)3(Me-PN3PTATA)] (1) to the gold
surface.
Table 3. Löwdin partial charges of [Mo(CO)3(Me-PN3PTATA)] (1) and
[Mo(CO)3(Me-PN3PTATA)]@Au(111).
Figure 11: Leading term of EDA-NOCV of 1@Au(111) depicted as deformation
density. Regions of electron depletion and accumulation are shown in blue and
red, respectively.
1
1@Au(111)
∆
Mo
CO
Me-PN3P
TATA
sum
-1.76
0.45
1.25
0.06
0
-1.67
0.53
1.44
1.35
1.64
0.09
0.08
0.19
1.29
1.64
Looking closer at the bulk IR and IRRAS data of complex 1,
it becomes apparent that the three carbonyl stretching modes
exhibit distinctly different frequency shifts if 1 is deposited on the
surface; i.e., whereas the antisymmetric B1 and A1(2) modes shift
by 31 - 36 cm-1 to higher energies, the totally symmetric A1(1)
stretch only exhibits a shift of 8 cm-1 (Table 2). Obviously the net
flow of charge from the Mo(0) center to the Au substrate affects
the three vibrations differently. figure 12 describes a possible
explanation for this observation: charge depletion on the metal
center leads to an overall shift of all three bands to higher energy,
leading to an overall shortening of C-O bond distances and, thus,
to a global positive frequency shift. We associate this shift with a
change in “static” activation upon deposition of the metal complex
on the Au(111) surface (fig. 12, top and middle). A second effect
modulating vibrational frequencies derives from a charge flow
from the metal into the ligand π* orbitals when the C-O bonds are
elongated. This (dynamic) effect flattens the potential curve,
reduces the corresponding force constant and thus acts to lower
the CO-stretching frequency (“dynamic” activation). Importantly, it
only comes into play if the vibrational coordinate is associated
with a net flow of charge between the metal and the ligands. This,
however, only applies to the totally symmetric A1(1) vibration. For
the other two vibrations, only a redistribution of charge density
occurs along the corresponding nuclear coordinate; i.e., between
the two equatorial ligands (B1) or between the equatorial ligands
To further investigate the changes in electronic structure
upon surface adsorption we performed an energy decomposition
analysis (EDA)[70] for the binding between the two fragments
complex 1 and Au surface. To this end total binding energy ∆E
between the fragments (about -40 kcal/mol, i.e., between typical
bond dissociation energies and H-bonding) is decomposed
according to:
∆ꢀ ꢁ ∆ꢀꢂꢃꢄꢂ ꢅ ∆ꢀꢆꢇꢄꢃꢈꢉ ꢅ ∆ꢀꢊꢃꢋ
∆Eprep consists of the energy necessary to promote the fragments
from their relaxed state to their geometry and electronic state in
the complex and ∆Esteric corresponds to a so-called steric
repulsion term consisting of classical electrostatic interactions
and nonclassical Pauli repulsion. The orbital interaction energy
∆Eorb, finally, is recognized to reflect covalent bonding. It can be
decomposed into contributions from natural orbitals for chemical
valence (NOCV).[70] These are made up by donor-acceptor pairs
of eigenvectors associated with an eigenvalue reflecting the
energy contribution of each pair. Note, however, that these
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
Conclusion
Establishing a new approach to small molecule activation, a
molybdenum(0) triscarbonyl complex supported by a Me-PN3P
ligand was synthesized, connected to a TATA platform, and
characterized in solution, bulk material as well as adsorbed on
Au(111). Applying different surface-spectroscopic methods (XPS,
NEXAFS, IRRAS) the zerovalent oxidation state of the
molybdenum center and the perpendicular orientation of the
complex with respect to the surface were demonstrated.
Importantly, the IRRAS measurements revealed a distinct
influence of the gold substrate on the activation of the carbonyl
ligands. Even though the static activation was found to be smaller
on the surface than in bulk material due to the electron-
withdrawing character of the Au substrate, a dynamic back-
transfer of electronic charge from the substrate to the Mo complex
could be evidenced, enhancing the (dynamic) polarizability of the
metal center. The latter effect could become important in the case
of chemical transformations (e.g., protonation reactions) involving
ligands bound to surface-adsorbed complexes, lowering the
activation energies associated with these processes.
Figure 12: Influence of static and dynamic activation on the carbonyl stretching
modes of [Mo(CO)3(Me-PN3PTATA)] (1) (@Au(111)).
and the axial ligand (A1(2)). Thus, only the A1(1) mode is
susceptible to a change in dynamic activation. From the reduced
positive frequency shift of the A1(1) mode we assume that the
dynamic activation in the surface-deposited complex 1 is higher
than in the free complex and thus acts against the global positive
shift due to the change in static activation (fig. 12, bottom). The
increase in dynamic activation can in turn be explained by the fact
that the metal complex is coupled to a metallic substrate; i.e.,
although this substrate statically withdraws electron density from
the complex, it can dynamically back-donate electron density to
this complex via the linker unit if the ligands are elongated.
Figure 13 shows the C-H region of the computed and
measured IR spectra. The aliphatic C-H stretching vibrations are
located at 2960 cm-1, 2929 cm-1 and 2856 cm-1 in the IRRA
spectrum. Because of the free mobility of the octyl side chains on
the surface (vide supra), the shape of the aliphatic C-H region is
similar to that of the bulk IR. The bands at 3076 cm-1 and 3066
cm-1 can be assigned to aromatic C-H stretches of the phosphine
phenyl rings. In conclusion the results of vibrational spectroscopy
support the STM, XPS and NEXAFS measurements.
Experimental Section
General synthetic procedures
Commercially available starting materials and solvents were used
as received. Water and oxygen sensitive reagents were handled
in an M. Braun Labmaster 130 Glovebox under N2. Moisture and
air sensitive reactions were carried out in dried solvents under N2
atmosphere using Schlenk techniques. Dimethylacetamide was
dried over molecular sieve (3 Å) under N2. NEt3, toluene, DCM
and n-hexane were dried over CaH2, THF over LiAlH4 under Ar
and were distilled prior to use.
Column chromatography
Purification of crude products was performed using a flash
chromatography Isolera One Spektra System (Co. Biotage).
SNAP Ultra cartridges (spherical silica gel, HP-Sphere; 10 g, 25 g,
50 g) were used according to the amount of crude product (Co.
Biotage). Depending in the Rf value of the product the flash
chromatography was performed with a solvent gradient.
IR and Raman spectroscopy
IR spectra were recorded on
a Bruker Alpha-P ATR-IR
Spectrometer. Raman spectra were measured on a Bruker IFS
66 RA 106.
NMR spectroscopy
1
The H, 13C and 31P NMR spectra were recorded in deuterated
solvents on a Bruker Avance 400 Puls Fourier Transform
spectrometer at 300 K and are referenced to the solvent. 31P NMR
spectra were referenced to H3PO4 85% (δ(31P)=0 ppm) as
substitutive standard.
Single crystal structure analysis
Data collections were performed at 170 K using an imaging plate
diffraction system (IPDS-2 from STOE & CIE) using Mo-Kα
Figure 13: C-H region of computed and measured vibrational spectra of
[Mo(CO)3(Me-PN3PTATA)] (1) in bulk material and adsorbed on Au(111).
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
efficiency was set for the half-wave at 3000 cm-1 for analysis of
the area from 2000 cm-1 to 1000 cm-1. All spectra were recorded
with 4 cm-1 resolution.
Processing of IRRAS and PM-IRRAS data was carried out using
the OPUS software Version 6.5 (Bruker, Germany). Baseline
correction of the resulting IRRAS data was performed by the
rubber band method in an interactive mode. PM-IRRAS data were
processed by the implicit removal of the Bessel function through
manual baseline correction.
radiation. Structure solutions were performed with SHELXT and
structure refinements were done against F2 using SHELXL-
2014.[71,72] A numerical absorption correction was applied using
programs X-RED and X-SHAPE of the program package X-
Area.[73] All non-hydrogen atoms were refined anisotropically. The
C-H hydrogen atoms were positioned with idealized geometry
and were refined isotropic with Uiso(H) = 1.2 Ueq(C) (1.5 for methyl
H atoms) using a riding model. The complex is located on a 2-fold
rotation axis and therefore, the trimethylsilyl group is disordered
in two positions because of symmetry. The asymmetric unit also
contain two acetonitrile solvate molecules. For the figures the
CYLview software was used.[74] CCDC-1824953 (3) and CCDC-
XPS & NEXAFS
The XPS and NEXAFS measurements were performed at the
BESSY II synchrotron radiation facility using the PREVAC
endstation at the beamline HE-SGM. The experimental station is
equipped with a hemispherical VG Scienta R3000 photoelectron
analyzer. The energy resolution E/DE of the beamline with 150
mm slits is 800. XP survey spectra were secured at 700 eV photon
energy using an analyzer pass energy of 100 eV, whereas for the
C 1s, Mo 3d and P 2p spectra the photon energy used was 350
eV with pass energy of 50 eV. For N 1s spectra the photon energy
was at 500 eV with pass energy of 50 eV.
All spectra were acquired at normal electron emission. For
determination of the relative composition of the TATA adlayers,
the XP spectra were energy-corrected using the Au 4f7/2 line at a
binding energy of 84.0 eV as reference. Background correction
was performed using a combination of a Shirley and a linear
background for all signals. Peak fitting was performed using the
program CASA XPS. The fitting parameter are shown in table S
6.
1824954
([Mo(CO)3(H-PN3PTMS)]·NCCH3)
contain
the
supplementary crystallographic data for this paper. These data
can be obtained free charge from the Cambridge Crystallographic
Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif.
Elemental analyses
Elemental analyses were performed using a Euro Vector CHNS-
O-element analyzer (Euro EA 3000) or a vario MICRO cube (Co.
Elementar Analysensysteme).
Gold Substrates
Glass substrates with a 50 Å titanium adlayer and a 200 nm
evaporated gold film from EMF corporation (Ithaca, NY) were
used for IRRAS measurements. STM, XPS and NEXAFS
measurements were made with sputtered Au(111) single crystals.
Preparation of Monolayers
To correct for the photon flux of the NEXAFS measurements, all
spectra were divided by the spectrum obtained for a freshly
sputtered clean gold substrate and then edge-step normalized
(using the average intensities for the C K-edge between 275 ±0.5
eV and 320 ± 0.5 eV and for the N K-edge between 395 ±0.5 eV
and 420 ±0.5 eV as pre- and post-edge).
Monolayers of [Mo(CO)3(Me-PN3PTATA)] were prepared by
immersing Au(111) substrates in 0.5 mM solutions of the
respective compound in toluene (Uvasol, Merck) at room
temperature. After 5-10 mins of immersion the sample was
removed from the solution, rinsed with toluene and dried in a
stream of nitrogen gas.
Computational Details
STM
Throughout the whole study a reduced model of 1 was used with
propyl instead of octyl moieties on the TATA platform to reduce
turnover times.
STM measurements were performed with a PicoPlus STM
(Agilent, Inc., Santa Clara, USA) at room temperature with
mechanically cut Pt/Ir (70:30) tips.
The geometry optimizations and frequency calculations
necessary for the simulation of the IRRA spectra were obtained
with Gaussian09 Rev.D01.[75] Therefor the PBE0 hybrid DFA[76]
was used as recommended for second row transition metal
complexes in conjunction with the Ahlrichs def2-SVP basis set[77]
and Grimme’s D3 dispersion correction with Becke-Johnson
damping (D3BJ).[78,79] Furthermore all calculations used the
appropriate def2 effective core potential on molybdenum.[80] No
imaginary frequencies above 5 cm-1 were obtained which
indicates a minimum. The IRRA spectrum was then simulated by
only taking those components of the transition dipole moment
vectors into account that are collinear to the backbone axis of the
ligand which is assumed to be perpendicular to the surface.
Since the computation of the NEXAFS data was assumed to be
mostly invariant to conformational changes the molecule was
optimized in the gas phase with DFT in ORCA 4.0.1.[81,82] This was
also used for the calculation of the NEXAFS spectra. For the
optimization the GGA DFA BP86[83,84] was used with a def2-SVP
basis set with dispersion correction (D3BJ) and the resolution of
IRRAS
The surface adsorbed molecules were investigated by using a
Bruker VERTEX 70 FT-IR spectrometer equipped with a
Polarization Modulation Accessory (PMA) 50 unit (Bruker Optik
GmbH, Ettlingen, Germany). This instrument allows recording
IRRAS and PM-IRRAS data with a spectral range from 4000 down
to 800 cm-1. IRRAS data were collected with a liquid nitrogen
cooled MCT detector in a horizontal reflection unit for grazing
incidence (Bruker A518). The sample chamber was purged with
dry nitrogen before and during measurements. A deuterated
hexadecane-thiol SAM on Au(111) was used as a reference for
the background spectrum for conventional IRRA spectra. Each
spectrum contains 2048 averaged spectra. A p-polarized beam
at an incident angle of 80° to the surface normal w as used for
measurements. All spectra were recorded with 4 cm-1 resolution.
PM-IRRAS data were collected with the PMA 50 accessory using
a liquid nitrogen-cooled MCT detector. The PEM maximum
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
identity for additional speed.[85,86] With the optimized structures C-
1s and N-1s-core to valence electronic spectra were calculated.
This was done in the framework of TDDFT with the hybrid DFA
IR (ATR): ṽ = 3151 (w), 3002 (w), 2981 (m), 2933 (w), 1705 (ss),
1668 (w), 1558 (m), 1477 (w), 1464 (w), 1451 (w), 1419 (w), 1385
(s), 1365 (s), 1334 (s), 1269 (sh), 1268 (w), 1253 (m), 1197 (w),
1139 (ss), 1117 (ss), 1094 (m), 1040 (w), 1026 (m), 970 (m), 924
(w), 886 (m), 850 (m), 837 (s), 803 (m), 768 (s), 761 (m), 740 (m),
693 (w), 660 (m), 599 (m), 562 (m), 517 (w), 467 (w), 459 (w), 426
(w) cm-1.
B3LYP[87]
,
the def2-TZVPP basis set[77]
,
the RIJCOSX
approximation[88] and fine numerical integration grids (grid6 and
gridX6 in ORCA nomenclature). The orbital window from which
electrons were to be excited was restricted to the 1s orbital of the
atom of interest. Where necessary the orbital was previously
localized with the Pipek-Mezey localization scheme.[89] On this
atom the integral accuracy was increased and 80 roots with
electric quadrupole contributions computed. This was repeated
for every unique C and N atom in the molecule. Local symmetry
was exploited when appropriate so not every single atomic
spectrum had to be calculated. The influence of the C atoms from
the TATA-octyl moieties missing in this study was included by
assuming that they show the same spectral features as the central
C atom in the propyl moiety. Consequently the atomic spectra of
this atom were included multiple times to make up for the
deficiency of the model. All the resulting atomic spectra were
collected, scaled according to symmetry and summed up to yield
the spectrum of the whole molecule.
N,N’-Dimethyl-4-((trimethylsilyl)ethynyl)pyridine)-2,6-di-tert-
butyl-dicarbamate (8)
The synthesis was performed under nitrogen atmosphere. To di-
tert-butyl-(4-bromopyridine-2,6-diyl)bis(methylcarbamate)
(7)
(2.00 g, 4.80 mmol) , copper(I) iodide (190 mg, 998 µmol) and
tetrakis(triphenylphoshine)palladium(0) (382 mg, 331 µmol) was
added triethylamine (50 mL). Trimethylsilylacetylene (992 µL,
6.65 mmol) was added dropwise and the reaction mixture was
stirred for 3 d under reflux. Afterwards the suspension was filtered
through Celite and the filter cake was washed with THF. The
solvent was evaporated under reduced pressure and the crude
product was purified via automated column chromatography
(cyclohexane/ ethyl acetate + 1% TEA, 3-30 % ethyl acetate,
Rf = 0.52). The product was obtained as light brown solid (1.84 g,
4.24 mmol, 88 %).
Anal. calcd for C22H35N3O4Si: C, 60.9; H, 8.1; N, 9.7. Found: C,
61.7; H, 8.1; N, 9.1.
Electronic structure calculations on the surface-adsorbed
molecule were also conducted with ORCA and used the RPBE
DFA[90] which was parameterized to yield improved adsorption
and noncovalent interaction energies in conjunction with
1H NMR (400.1 MHz, CDCl3): δ = 7.51 (s, 2H, py H3,5), 3.34 (s,
6H, N(CH3)), 1.53 (s, 18H, C(CH3)3), 0.23 (s, 9H, Si(CH3)3) ppm.
13C NMR (100.6 MHz, CDCl3): δ = 154.4 (s, C=O), 152.9 (s, py
C2,6), 133.3 (s, py C4), 115.7 (s, py C3,5), 103.0 (s, C≡C(Si(CH3)3)),
98.0 (s, C≡C(Si(CH3)3)), 81.4 (s, C(CH3)3), 34.0 (s, N(CH3)), 28.5
(s, C(CH3)3), -0.09 (s, Si(CH3)3)) ppm.
dispersion correction,
a def2-SVP basis set and the RI
approximation as above. The model was built from a hexagonal
cut from an Au(111) surface slab with one surface layer and the
propyl-substituted variant of (1). The geometry optimization was
conducted with the semiempirical GFN-xTB tight binding code.[91]
IR (ATR): ṽ = 2999 (w), 2975 (m), 2931 (w), 2161 (w), 1701 (ss),
1667 (w), 1594 (m), 1545 (m), 1474 (m), 1458 (sh), 1448 (sh),
1426 (w), 1397 (s), 1392 (s), 1365 (m), 1338 (s), 1314 (m), 1247
(m), 1141 (sh), 1135 (ss), 1107 (sh), 1040 (w), 1024 (m), 1012
(w), 929 (m), 915 (m), 888 (m), 854 (sh), 840 (s),726 (s), 727 (m),
701 (w), 657 (m), 608 (m), 589 (m), 483 (w), 460 (w), 422 (sh),
413 (w) cm-1.
Syntheses
4-Bromopyridine-2,6-dicarboxylic-acid-diethylester
(4),
4-
bromopyridine-2,6-dicarboxylic-acid-dihydrazide (5) , di-tert-butyl
(4-bromopyridine-2,6-diyl)-dicarbamate (6)[56] and 4,8,12-tri-n-
N,N’-Dimethyl-4-((trimethylsilyl)ethynyl)pyridine-2,6-diamine
(9)
The synthesis was performed under nitrogen atmosphere. To di-
octyl-4,8,12-triazatriangulenium
synthesized according to the literature.
tetrafluoroborate[49]
were
tert-butyl-(4-bromopyridine-2,6-diyl)bis(methylcarbamate)
(8)
(2.15 g, 4.96 mmol) and dry ZnBr2 (9.74 g, 43.3 mmol) was added
dichloromethane (40 mL). The suspension was stirred for 7 h
under reflux and overnight at rt. Afterwards distilled water (20 mL)
was added and the mixture was stirred for 1 h. The organic layer
was separated and the aqueous layer was extracted with
dichloromethane (3 x 30 mL).The combined organic layer was
dried over MgSO4 and the solvent was evaporated under reduced
pressure. The crude product was purified by automated column
chromatography (cyclohexane/ethyl acetate, + 1% TEA, 18-
100 % ethyl acetate, Rf = 0.47). The product was obtained as light
brown solid (758 mg, 3.25 mmol, 65 %).
N,N’-Dimethyl-4-bromopyridine-2,6-di-tert-butyl-dicarbamate
(7) The synthesis was performed under nitrogen atmosphere. To
a suspension of NaH (571 mg, 23.8 mmol) in dimethylacetamide
(30 mL) di-tert-butyl (4-bromopyridine-2,6-diyl) dicarbamate (6)
(4.00 g, 10.3 mmol) in dimethylacetamide (25 mL) was added at
0 °C. After stirring for 5 min at 0 °C and 60 min a t rt methyliodide
(1.71 mL, 27.5 mmol) was added to the suspension. The reaction
mixture was stirred for 16 h at rt. Afterwards ethyl acetate
(150 mL) was added and the organic layer was washed with
aqueous 10percent citric acid (100 mL), a saturated NaHCO3
solution (100 mL) and brine (100 mL). The organic layer was dried
over sodium sulfate and the solvent was evaporated under
reduced pressure. The crude product was purified by automated
column chromatography (n-hexane/ethyl acetate, 8-66 % ethyl
acetate, Rf = 0.55). The product was obtained as a yellow oil
(4.00 g, 9.64 mmol, 94 %), which crystallized over time.
Anal. calcd for C17H26BrN3O4: C, 49.1; H, 6.3; N, 10.1. Found: C,
49.5; H, 6.3; N, 9.7.
Anal. calcd for C12H19N3Si: C, 61.8; H, 8.2; N, 18.0. Found: C,
62.1; H, 8.1; N, 17.7.
1H NMR (400.1 MHz, CDCl3): δ = 5.80 (s, 2H, py H3,5), 4.30 (br q,
3J=4.7 Hz, 2H, NH), 2.84 (d, 3J=5.3 Hz, 6H, N(CH3)), 0.24 (s, 9H,
Si(CH3)3) ppm.
13C NMR (100.6 MHz, CDCl3): δ = 159.1 (s, py C2,6), 133.3 (s, py
C4), 104.5 (s, C≡C(Si(CH3)3)), 96.9 (s, py C3,5), 95.5 (s,
C≡C(Si(CH3)3)), 29.3 (s, N(CH3)), 0.04 (s, Si(CH3)3)) ppm.
IR (ATR): ṽ = 3402 (br, m), 3376 (sh), 3271 (br, m), 3084 (br, w),
2957 (m), 2928 (m), 2901 (w), 2797 (w), 2163 (sh), 2152 (w), 1592
(m), 1555 (s), 1540 (s), 1481 (m), 1450 (m), 1400 (s), 1271 (w),
1246 (s), 1229 (sh), 1170 (m), 1094 (w), 1087 (w), 990 (m), 964
1H NMR (400.1 MHz, CDCl3): δ = 7.68 (s, 2H, py H3,5), 3.35 (s,
6H, N(CH3)), 1.53 (s, 18H, C(CH3)3) ppm.
13C NMR (100.6 MHz, CDCl3): δ = 154.1 (s, C=O), 153.2 (s, py
C2,6), 133.3 (s, py C4), 116.0 (s, py C3,5), 81.8 (s, C(CH3)3, 33.9 (s,
N(CH3)), 28.4 (s, C(CH3)3) ppm.
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
(m), 836 (s), 803 (s), 754 (m), 720 (w), 697 (w), 674 (w), 637 (m), Anal. calcd for C39H37MoN3O3P2Si: C, 59.9; H, 4.8; N, 5.4. Found:
609 (m), 567 (m), 517 (w), 489 (w), 455 (w), 409 (w) cm-1.
C, 59.7; H, 5.0; N, 5.5.
1H NMR (400.1 MHz, CDCl3): δ = 7.61-7.56 (m, 8H, ph Hortho),
7.44-7.35 (m, 12H, ph Hmeta,para), 6.32 (s, 2H, py H3,5), 2.97 (ps t,
JH-P=1.9 Hz, 6H, N(CH3)), 0.28 (s, 9H, Si(CH3)3) ppm.
N,N’-Bis(diphenylphosphino)-N,N’-dimethyl-4-
((trimethylsilyl)ethynyl)pyridine-2,6-diamine (2)
The synthesis was performed according to KIRCHNER et al.[58] and
13C NMR (100.6 MHz, CDCl3): δ = 228.3 (t, JC-P=5.0 Hz, trans-
2
2
C=O), 211.6 (t, JC-P=10.0 Hz, cis-C=O), 161.8 (ABX, py C2,6),
under
dinitrogen
atmosphere.
To
N,N’-dimethyl-4-
137.7 (ABX, Cipso), 132.0 (s, py C4), 130.9 (ABX, ph Cortho), 129.5
(s, ph Cpara), 128.4 (ABX, ph Cmeta), 103.4 (s, C≡C(Si(CH3)3)),
101.3 (ABX, py C3,5), 99.0 (s, C≡C(Si(CH3)3)), 37.4 (s, N(CH3)), -
0.06 (s, Si(CH3)3) ppm.
((trimethylsilyl)ethynyl)pyridine-2,6-diamine (9) (641 mg,
2.75 mmol) was added toluene (40 mL). After cooling to -20 °C n-
BuLi (2.5 M in n-hexane, 1.16 mL, 2.90 mmol) was added
dropwise and the solution was stirred for 2 h at rt. At – 60 °C
chlorodiphenylphosphine (605 mg, 2.75 mmol) was added and
the solution was first stirred for 2 h at rt and afterwards overnight
at 80 °C. The following steps were performed under air. The
reaction solution was allowed to cool down to rt and a saturated
NaHCO3 solution (8 mL) was added. The organic layer was
separated and the aqueous layer was washed with toluene
(15 mL). The combined organic layer was dried over sodium
sulfate and the solvent was evaporated under reduced pressure.
Under dinitrogen atmosphere, the yellow-brown intermediate
product was dissolved in toluene (40 mL) and cooled to -20 °C.
To the solution n-BuLi (2.5 M in n-hexane, 1.16 mL, 2.90 mmol)
was added dropwise and the solution was stirred for 2 h at rt.
Again the mixture was cooled to -60 °C and
chlorodiphenylphosphine (605 mg, 2.75 mmol) was added. The
reaction solution was stirred for 2 h at rt and afterwards overnight
at 80 °C. As mentioned above, the following work-up was
performed under air. A saturated NaHCO3 solution (8 mL) was
added to the reaction mixture. The organic layer was separated
and the aqueous layer was washed with toluene (15 mL). The
combined organic layer was dried over sodium sulfate and the
solvent was evaporated under reduced pressure. The crude
product was recrystallized from acetonitrile. The solid was filtered,
washed with acetonitrile and dried under vacuum. The product
was obtained as colorless solid (1.22 g, 2.03 mmol, 74 %).
Anal. calcd for C36H37N3P2Si: C, 71.9; H, 6.2; N, 7.0. Found: C,
71.4; H, 6.3; N, 6.9.
31P NMR (162.0 MHz, CDCl3): δ = 133.0 (s, 2P, PPh2) ppm.
IR (ATR): ṽ = 3073 (w), 3057 (w), 3012 (w), 2985 (w), 2916 (w),
2865 (w),2160 (w), 2152 (w), 1969 (s), 1859 (s), 1837 (ss), 1584
(m), 1525 (m), 1470 (m), 1454 (sh), 1433 (m), 1402 (s), 1376 (m),
1329 (w), 1305 (w), 1263 (m), 1243 (s), 1193 (m), 1183 (m), 1166
(m), 1080 (m), 1024 (w), 1006 (s), 961 (m), 918 (w), 844 (s), 815
(m), 788 (m), 758 (w), 740 (w), 721 (m), 691 (s), 656 (m), 637 (m),
620 (w), 602 (m), 582 (m), 574 (m), 559 (m), 533 (m), 510 (s), 476
(s), 439 (m), 428 (w), 408 (w), 391 (m) cm-1.
FT-Raman: ṽ = 3056 (w), 2965 (w), 2903 (w), 2155 (s), 1968 (m),
1836 (w), 1587 (s), 1571 (m), 1192 (w), 1027 (m), 998 (s), 988
(s), 659 (m), 561 (m), 476 (m), 460 (m), 424 (m), 419 (sh) cm-1.
[Mo(CO)3(Me-PN3PTATA)] (1) The synthesis was performed under
nitrogen atmosphere. First [Mo(CO)3(Me-PN3PTMS)] (3) (100 mg,
128 µmol) and water free KOH (44 mg, 782 µmol) was stirred at
rt in THF (50 mL). The deprotection reaction was followed by thin-
layer chromatography (neutral alox, cyclohexane/ethyl acetate:
6:1, Rf-value: 0.42). The following steps were performed in the
dark because of the instability of the TATA derivatives against UV
light. 4,8,12-Tri-n-octyl-4,8,12-triazatriangulentetrafluoroborate
(90 mg, 128 µmol) and THF (10 mL) was added and the reaction
mixture was stirred at 50 °C for 75 min. The progre ss was
followed by thin-layer chromatography (neutral alox,
cyclohexane/ethyl acetate: 6:1, Rf-value: 0.64). The reaction
mixture was filtered through basic alox in order to separate excess
of TATA salt and KOH. The solvent was evaporated under
reduced pressure. The following steps were performed under air.
The crude product was purified via column chromatography
(basic alox, cyclohexane/ ethyl acetate 95:5). The solvent was
evaporated under reduced pressure. The yellow-orange product
(111 mg, 83.6 µmol, 65 %) was dried in vacuum and stored in the
dark under nitrogen at -18 °C.
1H NMR (400.1 MHz, CDCl3): δ = 7.42-7.43 (m, 20H, ph Hall), 6.93
4
3
(d, J=2.5 Hz, 2H, py H3,5), 2.83 (d, JH-P=1.6 Hz, 6H, N(CH3)),
0.24 (s, 9H, Si(CH3)3) ppm.
2
4
13C NMR (100.6 MHz, CDCl3): δ = 159.7 (dd, JC-P=27.8, JC-
1
4
P=2.1, py C2,6), 137.3 (d, JC-P=15.8 Hz, ph Cipso), 132.8 (t, JC-
P=3.2 Hz, py C4), 132.2 (d, 2JC-P=20.8 Hz, ph Cortho), 129.0 (s, ph
Cpara), 128.5 (d, 3JC-P=5.9 Hz, ph Cmeta), 104.5 (s, C≡C(Si(CH3)3)),
102.5 (d, 3JC-P=21.6 Hz, py C3,5), 95.9 (s, C≡C(Si(CH3)3)), 34.0 (d,
2JC-P=8.8 Hz, N(CH3)), 0.05 (s, Si(CH3)3) ppm.
Anal. calcd for C79H88MoN6O3P2: C, 71.5; H, 6.7; N, 6.3. Found:
C, 71.4; H, 7.0; N, 6.5.
1H NMR (400.1 MHz, toluene-d8): δ = 7.53-7.48 (m, 8H, ph Hortho),
31P NMR (162.0 MHz, CDCl3): δ = 50.4 (s, 2P, PPh2) ppm.
IR (ATR): ṽ = 3069 (w), 3056 (w), 3002 (w), 2961 (w), 2927 (w),
2901 (w), 2856 (w), 2163 (w), 1580 (m), 1536 (s), 1478 (w), 1433
(m), 1423 (m), 1379 (s), 1366 (s), 1304 (w), 1260 (w), 1246 (m),
1230 (s), 1185 (m), 1149 (m), 1118 (w), 1091 (m), 1081 (m), 1026
(w), 986 (s), 955 (m), 918 (w), 843 (s), 815 (m), 762 (m), 741 (ss),
693 (ss), 667 (m), 657 (m), 630 (m), 618 (w), 588 (s), 544 (m),
535 (m), 501 (s), 474 (s), 453 (m), 425 (w), 406 (w) cm-1.
3
7.22 (t, J=8.3 Hz, 3H, phTATA Hpara) 7.09-7.05 (m, 8H, ph Hmeta),
7.01-6.99 (m, 4H, ph Hpara), 6.63 (d, 3J=8.4 Hz, 6H, phTATA Hmeta),
5.79 (s, 2H, py H3,5), 3.84 (ps t, 6H, N(CH2CH2(CH2)5CH3)), 2.11
(ps t,
JH-P=1.7 Hz, 6H, N(CH3)), 1.82 (ps quint, 6H,
N(CH2CH2(CH2)5CH3)),
N(CH2CH2(CH2)5CH3)),
N(CH2CH2(CH2)5CH3)) ppm.
1.29-1.18
0.90 (t,
(m,
30H,
9H,
3J=7.0
Hz,
13C NMR (100.6 MHz, toluene-d8): δ = 227.2 (t, JC-P=5.0 Hz,
2
2
[Mo(CO)3(Me-PN3PTMS)] (3) The synthesis was performed
according to KIRCHNER et al.[55] and under nitrogen atmosphere.
The precursor [Mo(CO)3(AcN)3] was obtained by stirring
[Mo(CO)6] (132 mg, 499 µmol) in acetonitrile (5 mL) under reflux
for 1.5 h. The solution was allowed to cool down to rt and the Me-
PN3PTMS ligand (2) (300 mg, 499 µmol) in acetonitrile (5 mL) was
added. Afterwards the reaction mixture was stirred at rt overnight.
The suspension was filtered and the precipitate was washed with
a small amount of acetonitrile. After drying under vacuum the
product was obtained as orange powder (233 mg, 298 µmol,
60 %).
trans-C=O), 212.0 (t, JC-P=9.9 Hz, cis-C=O), 161.4 (ABX, py
C2,6), 141.1 (s, phTATA Cortho), 138.4 (ABX, ph Cipso), 132.8 (s, py
C4), 131.1 (ABX, ph Cortho), 129.2 (s, ph Cpara), 128.9 (s, phTATA
Cpara), 128.3 (ABX, ph Cmeta), 110.1 (s, phTATA Cipso), 105.6 (s,
phTATA Cmeta), 101.7 (ABX, py C3,5), 97.9 (s, C≡C(TATA)), 83.6 (s,
C≡C(TATA)), 46.8 (s, N(CH2CH2(CH2)5CH3)), 36.2 (s, N(CH3)),
32.3 (s, N((CH2)5CH2CH2CH3)), 29.8 (s, N((CH2)3CH2CH2
(CH2)2CH3)), 29.4 (s, TATA C), 27.3 (s, N((CH2)2CH2(CH2)4CH3)),
26.0 (s, N(CH2CH2(CH2)5CH3)), 23.1 (s, N((CH2)6CH2CH3)), 14.3
(s, N((CH2)7CH3)) ppm.
31P NMR (162.0 MHz, toluene-d8): δ = 133.0 (s, 2P, PPh2) ppm.
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
[19] L. A. Wickramasinghe, T. Ogawa, R. R. Schrock, P. Müller, J.
Am. Chem. Soc. 2017, 139, 9132–9135.
[20] N. Stucke, B. Flöser, T. Weyrich, F. Tuczek, Eur. J. Inorg.
Chem. 2018.; 10.1002/ejic.201701326.
[21] W. Zhang, W. Lai, R. Cao, Chem. Rev. 2017, 117, 3717–3797.
[22] R. D. Milton, R. Cai, S. Abdellaoui, D. Leech, A. L. de Lacey,
M. Pita, S. D. Minteer, Angew. Chem., Int. Ed. 2017, 56, 2680–
2683.; Angew. Chem. 2017, 129, 2724–2727.
IR (ATR): ṽ = 3074 (w), 3055 (w), 2948 (m), 2921 (m), 2850 (m),
1964 (m), 1861 (s), 1839 (s), 1613 (m), 1579 (m), 1532 (m), 1480
(m), 1454 (m), 1433 (m), 1393 (m), 1373 (m), 1305 (w), 1263 (m),
1243 (m), 1210 (w), 1166 (m), 1146 (sh), 1084 (m), 1047 (m),
1027 (w), 990 (w), 962 (w), 929 (w), 912 (w), 844 (w), 816 (w),
789 (m), 761 (w), 744 (w), 721 (m), 711 (m), 691 (m), 657 (w), 636
(m), 601 (m), 584 (m), 559 (m), 525 (w), 508 (m), 479 (m), 436
(w), 418 (w), 409 (w), 396 (w) cm-1.
[23] G. J. Leigh, C. J. Pickett, J. Chem. Soc., Dalton Trans. 1977,
FT-Raman: ṽ = 3058 (w), 2907 (br w), 2853 (w), 2205 (m), 1964
(m), 1850 (br, w), 1613 (sh), 1587 (s), 999 (m), 929 (w), 561 (w)
cm-1.
1797–1800.
[24] D. A. Offord, S. B. Sachs, M. S. Ennis, T. A. Eberspacher, J. H.
Griffin, C. E. D. Chidsey, J. P. Collman, J. Am. Chem. Soc.
1998, 120, 4478–4487.
[25] D. L. DuBois, Inorg. Chem. 1984, 23, 2047-2052.
[26] M. P. Shaver, M. D. Fryzuk, Adv. Synth. Catal. 2003, 345,
1061–1076.
Acknowledgements
[27] R. J. Burford, M. D. Fryzuk, Nat. Rev. Chem. 2017, 1, 26.
[28] J. M. Gottfried, Surf. Sci. Rep. 2015, 70, 259–379.
[29] E. Ludwig, H. Naggert, M. Kalläne, S. Rohlf, E. Kröger, A.
Bannwarth, A. Quer, K. Rossnagel, L. Kipp, F. Tuczek, Angew.
Chem., Int. Ed. 2014, 53, 3019–3023.; Angew. Chem. 2014,
126, 3063-3067.
[30] H. Naggert, J. Rudnik, L. Kipgen, M. Bernien, F. Nickel, L. M.
Arruda, W. Kuch, C. Näther, F. Tuczek, J. Mater. Chem. C
2015, 3, 7870–7877.
[31] T. G. Gopakumar, M. Bernien, H. Naggert, F. Matino, C. F.
Hermanns, A. Bannwarth, S. Mühlenberend, A. Krüger, D.
Krüger, F. Nickel, W. Walter, R. Berndt, W. Kuch, F. Tuczek,
Chem. Eur. J. 2013, 19, 15702–15709.
The authors would like to thank the HZB for provision of beamtime
at the BESSYII/HE-SGM and Christof Wöll for the provision of the
Prevac endstation. Furthermore the authors would like to thank
Kai Uwe Clausen and Imke Reuther for synthetic work performed
during their bachelor’s theses on project “Möwe”.
Keywords: Small molecule activation • Carbonyl complexes •
Surface chemistry • Surface spectroscopy • Vibrational
spectroscopy
[32] K. Flechtner, A. Kretschmann, H.-P. Steinrück, J. M. Gottfried,
J. Am. Chem. Soc. 2007, 129, 12110–12111.
[33] W. Hieringer, K. Flechtner, A. Kretschmann, K. Seufert, W.
Auwärter, J. V. Barth, A. Görling, H.-P. Steinrück, J. M.
Gottfried, J. Am. Chem. Soc. 2011, 133, 6206–6222.
[34] T. Miyamachi, M. Gruber, V. Davesne, M. Bowen, S. Boukari,
L. Joly, F. Scheurer, G. Rogez, T. K. Yamada, P. Ohresser, E.
Beaurepaire, W. Wulfhekel, Nat. Commun. 2012, 3, 938.
[35] H. Jacob, K. Kathirvel, F. Petersen, T. Strunskus, A.
Bannwarth, S. Meyer, F. Tuczek, Langmuir 2013, 29, 8534–
8543.
[36] J. Liu, M. Kind, B. Schüpbach, D. Käfer, S. Winkler, W. Zhang,
A. Terfort, C. Wöll, Beilstein J. Nanotechnol. 2017, 8, 892–905.
[37] W. Azzam, P. Cyganik, G. Witte, M. Buck, C. Wöll, Langmuir
2003, 19, 8262–8270.
[38] B. Lüssem, L. Müller-Meskamp, S. Karthäuser, R. Waser, M.
Homberger, U. Simon, Langmuir 2006, 22, 3021–3027.
[39] U. Jung, O. Filinova, S. Kuhn, D. Zargarani, C. Bornholdt, R.
Herges, O. Magnussen, Langmuir 2010, 26, 13913–13923.
[40] J. P. Collman, N. K. Devaraj, C. E. D. Chidsey, Langmuir 2004,
20, 1051–1053.
[41] B. Baisch, D. Raffa, U. Jung, O. M. Magnussen, C. Nicolas, J.
Lacour, J. Kubitschke, R. Herges, J. Am. Chem. Soc. 2009,
131, 442–443.
[42] U. Jung, S. Kuhn, U. Cornelissen, F. Tuczek, T. Strunskus, V.
Zaporojtchenko, J. Kubitschke, R. Herges, O. Magnussen,
Langmuir 2011, 27, 5899–5908.
[43] S. Kuhn, B. Baisch, U. Jung, T. Johannsen, J. Kubitschke, R.
Herges, O. Magnussen, Phys. Chem. Chem. Phys. 2010, 12,
4481–4487.
[44] S. Katano, Y. Kim, H. Matsubara, T. Kitagawa, M. Kawai, J.
Am. Chem. Soc. 2007, 129, 2511–2515.
[45] T. Weidner, M. Zharnikov, J. Hoβbach, D. G. Castner, U.
Siemeling, J. Phys. Chem. C 2010, 114, 14975–14982.
[46] U. Glebe, J. E. Baio, L. Árnadóttir, U. Siemeling, T. Weidner,
ChemPhysChem 2013, 14, 1155–1160.
[1] B. Milani, G. Licini, E. Clot, M. Albrecht, Dalton Trans. 2016,
45, 14419–14420.
[2] K. Arashiba, Y. Miyake, Y. Nishibayashi, Nat. Chem. 2011, 3,
120–125.
[3] D. V. Yandulov, R. R. Schrock, Science 2003, 301, 76–78.
[4] W. B. Tolman (Ed.) Small Molecule Activation, Wiley-VCH,
Weinheim, 2006.
[5] J. S. Anderson, J. Rittle, J. C. Peters, Nature 2013, 501, 84–
87.
[6] M. Réglier, C. Jorand, B. Waegell, J. Chem. Soc., Chem.
Commun. 1990, 107, 1752–1755.
[7] M. Rolff, J. Schottenheim, G. Peters, F. Tuczek, Angew.
Chem., Int. Ed. 2010, 49, 6438–6442.; Angew. Chem. 2010,
122, 6583–6587.
[8] F. Ungváry, Coord. Chem. Rev. 1997, 167, 233–260.
[9] B. A. MacKay, M. D. Fryzuk, Chem. Rev. 2004, 104, 385–401.
[10] B. K. Burgess, D. J. Lowe, Chem. Rev. 1996, 96, 2983–3011.
[11] K. Arashiba, E. Kinoshita, S. Kuriyama, A. Eizawa, K.
Nakajima, H. Tanaka, K. Yoshizawa, Y. Nishibayashi, J. Am.
Chem. Soc. 2015, 137, 5666–5669.
[12] A. Eizawa, K. Arashiba, H. Tanaka, S. Kuriyama, Y. Matsuo, K.
Nakajima, K. Yoshizawa, Y. Nishibayashi, Nat. Commun.
2017, 8, 14874.
[13] K. Arashiba, A. Eizawa, H. Tanaka, K. Nakajima, K.
Yoshizawa, Y. Nishibayashi, Bull. Chem. Soc. Jpn. 2017, 90,
1111–1118.
[14] S. E. Creutz, J. C. Peters, J. Am. Chem. Soc. 2014, 136,
1105–1115.
[15] T. J. Del Castillo, N. B. Thompson, J. C. Peters, J. Am. Chem.
Soc. 2016, 138, 5341–5350.
[16] J. Fajardo, J. C. Peters, J. Am. Chem. Soc. 2017, 139, 16105–
16108.
[17] S. Kuriyama, K. Arashiba, K. Nakajima, Y. Matsuo, H. Tanaka,
K. Ishii, K. Yoshizawa, Y. Nishibayashi, Nat. Commun. 2016, 7,
12181.
[18] S. Kuriyama, K. Arashiba, H. Tanaka, Y. Matsuo, K. Nakajima,
K. Yoshizawa, Y. Nishibayashi, Angew. Chem., Int. Ed. 2016,
55, 14291–14295.; Angew. Chem., 2016, 128, 14503-14507.
[47] K.-Y. Chen, O. Ivashenko, G. T. Carroll, J. Robertus, J. C. M.
Kistemaker, G. London, W. R. Browne, P. Rudolf, B. L.
Feringa, J. Am. Chem. Soc. 2014, 136, 3219–3224.
[48] M. Valášek, M. Lindner, M. Mayor, Beilstein J. Nanotechnol.
2016, 7, 374–405.
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
[49] B. W. Laursen, F. C. Krebs, Chem. Eur. J. 2001, 7, 1773–
1783.
[72] G. M. Sheldrick, Acta Crystallogr., Sect. C: Struct. Chem.
2015, 71, 3–8.
[50] S. Lemke, S. Ulrich, F. Claußen, A. Bloedorn, U. Jung, R.
[73] X-Area, Version 1.44. Program Package for Single Crystal
Measurements, STOE & CIE GmbH, Darmstadt, Germany,
2008.
Herges, O. M. Magnussen, Surface Science 2015, 632, 71–76.
[51] J. Kubitschke, C. Näther, R. Herges, Eur. J. Org. Chem. 2010,
2010, 5041–5055.
[74] C. Y. Legault, CYLview, 1.0b, Université de Sherbrooke, 2009,
[52] H. Jacob, S. Ulrich, U. Jung, S. Lemke, T. Rusch, C. Schütt, F.
Petersen, T. Strunskus, O. Magnussen, R. Herges, F. Tuczek,
Phys. Chem. Chem. Phys. 2014, 16, 22643–22650.
[53] R. G. Greenler, J. Chem. Phys. 1966, 44, 310–315.
[54] W. Schirmer, U. Flörke, H.-J. Haupt, Z. anorg. allg. Chem.
1987, 545, 83–97.
[55] D. Benito-Garagorri, E. Becker, J. Wiedermann, W. Lackner,
M. Pollak, K. Mereiter, J. Kisala, K. Kirchner, Organometallics
2006, 25, 1900–1913.
[56] M. Nettekoven, C. Jenny, Org. Process Res. Dev. 2003, 7, 38–
43.
[57] R. Kaul, Y. Brouillette, Z. Sajjadi, K. A. Hansford, W. D. Lubell,
J. Org. Chem. 2004, 69, 6131–6133.
[58] S. R. M. M. de Aguiar, B. Stöger, E. Pittenauer, M.
Puchberger, G. Allmaier, L. F. Veiros, K. Kirchner, J.
Organomet. Chem. 2014, 760, 74–83.
[59] F. L. Otte, S. Lemke, C. Schütt, N. R. Krekiehn, U. Jung, O. M.
Magnussen, R. Herges, J. Am. Chem. Soc. 2014, 136, 11248–
11251.
http://www.cylview.org.
[75] Gaussian 09, Revision D.01,. M. J. Frisch, G. W. Trucks, H. B.
Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G.
Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H.
Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J.
Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr., J.
E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K.
N. Kudin, V. N. Staroverov, T. Keith, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S.
Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene,
J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R.
Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R.
Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K.
Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J.
Dannenberg, S. Dapprich, A. D. Daniels, O. Farkas, J. B.
Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox.; Gaussian Inc.,
Wallingford CT, 2013.
[60] P. Schober, R. Soltek, G. Huttner, L. Zsolnai, K. Heinze, Eur. J.
Inorg. Chem. 1998, 1998, 1407–1415.
[76] C. Adamo, V. Barone, J. Chem. Phys. 1999, 110, 6158–6170.
[77] F. Weigend, R. Ahlrichs, Phys. Chem. Chem. Phys. 2005, 7,
3297–3305.
[78] S. Grimme, J. Antony, S. Ehrlich, H. Krieg, J. Chem. Phys.
2010, 132, 154104.
[79] S. Grimme, S. Ehrlich, L. Goerigk, J. Comput. Chem. 2011, 32,
1456–1465.
[80] D. Andrae, U. Huermann, M. Dolg, H. Stoll, H. Preu, Theoret.
Chim. Acta 1990, 77, 123–141.
[81] F. Neese, WIREs Comput. Mol. Sci. 2012, 2, 73–78.
[82] F. Neese, WIREs Comput. Mol. Sci. 2018, 8, e1327.
[83] A. D. Becke, Phys. Rev. A 1988, 38, 3098–3100.
[84] J. P. Perdew, Phys. Rev. B 1986, 33, 8822–8824.
[85] K. Eichkorn, O. Treutler, H. Öhm, M. Häser, R. Ahlrichs, Chem.
Phys. Lett. 1995, 240, 283–290.
[86] F. Neese, J. Comput. Chem. 2003, 24, 1740–1747.
[87] A. D. Becke, J. Chem. Phys. 1993, 98, 5648–5652.
[88] F. Neese, F. Wennmohs, A. Hansen, U. Becker, Chem. Phys.
2009, 356, 98–109.
[89] J. Pipek, P. G. Mezey, J. Chem. Phys. 1989, 90, 4916–4926.
[90] B. Hammer, L. B. Hansen, J. K. Nørskov, Phys. Rev. B 1999,
59, 7413–7421.
[91] S. Grimme, C. Bannwarth, P. Shushkov, J. Chem. Theory
Comput. 2017, 13, 1989–2009.
[61] P. S. Pregosin, R. W. Kunz, 31P and 13C NMR of Transition
Metal Phosphine Complexes, Springer, Heidelberg, 1979.
[62] H. Vu, M. R. Atwood, B. Vodar, J. Chem. Phys. 1963, 38,
2671–2677.
[63] G. Binnig, H. Rohrer, C. Gerber, E. Weibel, Phys. Rev. Lett.
1982, 49, 57–61.
[64] M. K. Rajumon, M. S. Hegde, C. N. R. Rao, Catal. Lett. 1988,
1, 351–360.
[65] S. O. Grim, L. J. Matienzo, Inorg. Chem. 1975, 14, 1014–1018.
[66] C. Battocchio, I. Fratoddi, M. V. Russo, V. Carravetta, S. Monti,
G. Iucci, F. Borgatti, G. Polzonetti, Surface Science 2007, 601,
3943–3947.
[67] C. Silien, M. Buck, G. Goretzki, D. Lahaye, N. R. Champness,
T. Weidner, M. Zharnikov, Langmuir 2009, 25, 959–967.
[68] S. Ulrich, U. Jung, T. Strunskus, C. Schütt, A. Bloedorn, S.
Lemke, E. Ludwig, L. Kipp, F. Faupel, O. Magnussen, R.
Herges, Phys. Chem. Chem. Phys. 2015, 17, 17053–17062.
[69] I. G. Hill, A. J. Mäkinen, Z. H. Kafafi, J. Appl. Phys. 2000, 88,
889–895.
[70] M. P. Mitoraj, A. Michalak, T. Ziegler, J. Chem. Theory
Comput. 2009, 5, 962–975.
[71] G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Adv. 2015,
71, 3–8.
This article is protected by copyright. All rights reserved.

10.1002/chem.201800911
Chemistry - A European Journal
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
Layout 1:
FULL PAPER
Text for Table of Contents
Author(s), Corresponding Author(s)*
Page No. – Page No.
Title
Layout 2:
FULL PAPER
Author(s), Corresponding Author(s)*
((Insert TOC Graphic here; max. width: 11.5 cm; max. height: 2.5 cm))
Page No. – Page No.
Title
Text for Table of Contents
This article is protected by copyright. All rights reserved.