Direct C-C coupling of two Ni-salphen complexes to yield dinickel-disalphen complexes with symmetric and non-symmetric substitution-patterns

Article abstract of DOI:10.1039/c5dt04612b

The synthesis of symmetric and non-symmetric 5,5′-linked disalophen Ni(ii) complexes by the Suzuki-Miyaura-reaction is reported. Also, the synthesis and structural characterization of four Ni(ii)-precursor complexes are presented. The 5-Br-substituted mononuclear complexes 4 and 5 are coupled to the pinacolborane substituted complexes 6 and 7 yielding the four dinuclear dinickel complexes 8-11 in good yields. The crystal structure of dinuclear complex 8 was obtained revealing a coplanar arrangement between the two salophen fragments. Electronic spectra as well as DFT-calculations on the ground states and excitation energies are reported and they reveal a small coupling between the electronically saturated Ni-salophen complexes.

Full text of DOI:10.1039/c5dt04612b

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Direct C-C coupling of two Ni-salophene complexes to yield
Dinickel-Disalophene complexes with symmetric and non-
symmetric substitution-patterns.
Received 00th January 20xx,
Accepted 00th January 20xx
B. E. C. Bugenhagena and M. H. Prosencb
DOI: 10.1039/x0xx00000x
www.rsc.org/
The synthesis of symmetric and non-symmetric 5,5’-linked disalophen Ni(II) complexes by the Suzuki-Miyaura-reaction is
reported. Also, the synthesis and structural charactrization of four Ni(II)-precursor complexes is presented. The 5-Br-
substitued mononuclear complexes 4 and 5 are coupled to the pinacole borane substituted complexes 6 and 7 yielding
the four dinuclear dinickel complexes 8-11 in good yields. The crystal structure of dinuclear complex 8 was obtained
revealing a coplanar arrangement between the two salophen fragments. Electronic spectra as well as DFT-calculations on
ground states and excitation energies are reported revealing a small coupling between the electronically saturated Ni-
salophen complexes.
fused salen-[18–21] and macrocyclic complexes.[22] Nevertheless,
a direct synthetic approach yielding salen-dimers and –
oligomers linked via a 5,5’-C-C bond has not been reported. As
Introduction
Oligonuclear salen-complexes gained
a lot of attention
mentioned before, oligosalen-complexes with this particular
bonding-pattern may exhibit unique combination of
recently, since their unique combination of an easy-to-modify
non-innocent ligand with a very broad range of the central
metal-ions, ranging from alkali- over 3d metal- to lanthanide-
ions.[1,2] Due to this versatility this class of compounds has
been investigated for a variety of applications and properties,
including metal-organic frameworks,[3,4] catalysis,[5,6] and
redox-behavior.[7–9] Furthermore, unique properties of salen-
complexes justify an established role in the research of
molecular based magnetism.[10–13] In a recent study, 5,5’-
a
properties and applications and thus their systematic
investigation is of special interest.
For the directed synthesis of multinuclear linked salen
complexes, a simple, standardized and versatile synthetic
protocol is necessary. Keeping a maximum flexibility of the
target compounds in mind, including unsymmetrical
substitution patterns of the salen- and salophen ligands, the
ideal approach would be a direct cross-coupling reaction of
dibromo-salophen-cobalt(II)-molecules
have
been
prefabricated building-blocks. One example for
a direct
oligomerized on a gold-surface in an Ullmann-type coupling
reaction under formation of 5,5’-C-C-coupled oligomeric
complex chains.[14] These molecular chains exhibited a unique
magnetic behavior, which is caused by the interaction of the
magnetic orbitals of the cobalt atoms with the extended π-
system of the ligand along the chain.[15] Based on this result, an
on-surface hetero-coupling strategy was developed to
coupling-reaction of two salen-complexes had been reported
in the literature, exploiting the olefin-methatesis-reaction,[23]
but only symmetric salen-complexes were achieved.
In this publication we present a method for the synthesis of
symmetric and unsymmetric 5,5’-bonded dinuclear nickel-
salophen-complexes by cross-coupling of mononuclear
precursor-complex building-blocks. In addition, the structural
and electronic properties of the synthesized mono- and
dinuclear nickel-complexes are investigated, especially
regarding the effects of an unsymmetrical substitution-pattern
combine
different
salophen-building-blocks
yielding
oligonuclear complexes for potential molecular spintronic
devices.[16]
A variety of oligonuclear salen- and salophen-complexes are
known to literature, e.g. covalently linked oligosalen-,[13,17]
and
a potential electronic communication between the
salophen moieties.
a.Institute for Inorganic and Applied Chemistry, University of Hamburg, Martin-
Luther-King-Platz 6, 20146 Hamburg, Germany
Results and Discussion
b.Institute for Physical Chemistry, TU Kaiserslautern, Erwin-Schrödinger-Str. 52,
67663 Kaiserslautern, Germany
In order to synthesize C-C coupled Ni(II) disalophen complexes
we employed the Suzuki-cross-coupling-reaction (Scheme 1) as
a versatile method to covalently link two molecules.[24,25] This
method was chosen for its tolerance towards functional
groups and its relatively mild reaction conditions, potentially
† Footnotes relaꢀng to the ꢀtle and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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Scheme 1: Suzuki-cross-coupling of two nickel-salophens. R1, R2: 5-tBu, 3,5-ditBu.
allowing the introduction of reactive metal-centers and in THF yielded the corresponding unsymmetrically substituted
substituents. Also, the absence of bivalent highly Lewis-acidic nickel-salophen precursor complexes . Aldehyde was
metal-ions during synthesis that could exchange with the synthesized in modified literature-protocol from 5-
coordinated nickel(II) ion is an advantage over other C-C cross- bromosalicylaldehyde.[28] All four precursor complexes were
4-
7
3
a
coupling reactions.
isolated in analytically pure form in good to excellent yields of
For the Suzuki-coupling the four precursor-complexes
4-
7
were 76-99 % (see experimental part). The Br-substituted complexes
synthesized (Scheme 2). Complexes
4
and
5
bear one Br-
4 and 5 were coupled to the pinacol borane derivatives 6 and 7
substituent each, in 6 and 7 pinacol borane groups are with yields given in Table 1.
attached. The latter substituent was chosen over the boronic The cross-coupling reaction was carried out using the complex
acid for its higher stability and its pH-neutrality, which is tetrakistriphenylphosphine palladium(0) as catalyst in the
important regarding the acid-sensitivity of the imine-group in presence of potassium carbonate as a base. For the reaction,
Schiff-base-ligands. The synthesis of the precursors was carried stock-solutions of the precursor-complexes (40 mmol/L) and
out following the procedure of Kleij et al. except for the choice the catalyst (10 mmol/L) in THF were prepared. Similar
of solvents.[3]
amounts of a Br-precursor and a BPin-precursor complex were
mixed in Schlenk-flasks and then treated with the catalyst
complex and an aqueous solution of potassium-carbonate.
After 24 hours of stirring at 70 °C the products were isolated.
Table 1: Numbers and yields of the coupling-products. The Br-carrying coupling
components in columns, the pinacol borane in rows.
4
5
6
7
8, 56 %
9, 66 %
10, 66 %
11, 93 %
Crystallography
Of the four mononuclear complexes
complex
be obtained after crystallization from CHCl3/n-hexane (
THF/n-hexane (5-7) or pyridine/n-hexane ( ). The structures of
and are presented in Figure 1. For crystallographic
4
-
7
and the dinuclear
Scheme 2: Two-step synthesis of the nickel-salophen
precursors. o-PDA=ortho-diaminobenzene.
8
, single-crystals suitable for structure analysis could
4),
The mono-imines
1 and 2 (Scheme 2) were generated from
8
ortho-diaminobenzene and the selected salicylic aldehyde
bearing one or two tert-butyl substituents.[26] The mono-imine
7
8
information see Table S1 in the supporting information.
Selected bond-lengths are listed in Table S2 along with
structural data retrieved from DFT-calculations. In all five
complexes the nickel-atom is four coordinate with Ni-N
(
1
or
nickelacetate-tetrahydrate in presence of triethylamine.[27]
Subsequent addition of solution of either 5-
2) was then added to a methanol solution of
a
bromosalicylaldehyde or 5-(pinacolboron)-salicylaldehyde (3)
distances from 1.8505(15) Å in
7 to 1.8624(26) Å in 4 and Ni-O
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Figure 1: Top: Molecular structure of 8, bottom: Molecular structure of 7. Hydrogen atoms and solvent-molecules are omitted for clarity, ellipsoids are at 50 % probability.
distances from 1.8315(13) Å in
7 to 1.8501(22) Å in 4. These and thus the alignment of the phenyl-rings is coplanar in the
geometry parameters are in accordance with those found in solid state. This conformation is presumably enforced by
literature (see Figure S1)[29]. Remarkably, the Ni-N1 and Ni-O1 crystal-packing effects, since the ordering in the crystal is
bonds are slightly longer than the corresponding Ni-N2 and Ni- dominated by shifted stacks of salophen-complexes. In these
O2 distances with differences ranging from 1.07 pm (
0.43 pm ( ) for the Ni-O distances and 0.07 pm ( ) to 0.97 pm two planar salophen units with a distance of 3.57 Å.
) for the Ni-N bonds. Although this difference is well within The C-C distance between the 6-membered rings in complex
the margin of error for compounds and , the fact that this is found to be 1.483(3) Å and corresponds to an elongated
6) to stacks, the C-C-bond of each dimer is sandwiched between
4
6
(
7
8
4,
6
8
trend is observed in all five crystal structures as well as double-bond between the phenyl ring fragments. This is in
reproduced by the DFT calculations makes this observation accordance with reported structures of biphenyls in the solid
significant and raises the question for the strength of a state,[30] where the repulsion between the two 6-membered
substituent influence. The electron-donating character (+I- rings lead to a long C-C bond.[31] The salophen-units in
effect) of the tBu- substituents opposed to the electron- an anti-conformation in the solid state.
withdrawing substituents (Bromine: -I-effect, Boron: -M-effect)
8 take
and the resulting shift of the electron density appears to be
the cause.
The structure of the dinuclear complex
8 exhibits a
crystallographic center of inversion on the phenyl-phenyl axis
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Spectroscopic characterization and DFT-studies
of conjugated polyphenyls, where the addition of one phenyl-
ring results in a bathochromic shift of about 30nm.[33–35]
Additionally, a striking feature of the UV/Vis-spectra is the
difference in absorption intensities between the mono- and
dinuclear complexes, which roughly double for all bands, so
All four precursor-complexes and the coupling-products 9/10
and 11 were subjected to NMR-analysis. Due to poor solubility
of the dinuclear compounds, 13C and correlation spectra
(COSY, HMBC, HSQC) were recorded only for the mononuclear
compounds with the consequence that an unambiguous
assignment of most of the signals was impossible for
εNi2~2·
the -systems of the salophen units; the dinuclear complexes
εNi1. These findings indicate a very weak conjugation of
π
rather behave like two independent complex molecules which
is not expected based on the spectra of polyphenyls. This
interpretation is further reinforced by the long phenyl-phenyl-
compounds 9/10 and 11. It catches the eye that the chemical
t
shifts of the imine-protons at the Bu-side of the molecule are
at lower field than the shifts of the protons at the Br/BPin-side.
This permits the assignment of the imine-protons in the
bond of 1.4831 nm found in the crystal structure of
8 and a
distortion of the coplanarity in the DFT-optimized gas-phase
structure found by a torsion of the phenyl-phenyl-torsion-
angle of roughly 36°.
spectra of
a good indication for the asymmetric substitution-pattern in
compound 9/10 since they are split into four clearly
9/10 and 11. The shift of the imine-protons are also
,
distinguishable singlets in the 1H-NMR spectra. For information
on peak-assignment, please refer to the supplementary
material (Table S4, Scheme S1).
Table 2: Absorption maxima and extinction coefficients extracted by Gaussian
deconvolution from the electronic spectra of compounds 4-9/10. λmax are given in nm,
e(λmax) are listed in brackets and are given in 104·L·mol-1·cm-1
.
band #1
λmax(ε)
band #2
λmax(ε)
band #3
λmax(ε)
band #4
λmax(ε)
band #5
λmax(ε)
4
5
519(3.7)
530(3.6)
525(2.6)
529(2.4)
534(12)
533(11)
494(3.5)
496(3.8)
491(4.8)
493(4.8)
502(12)
503(8.4)
445(6.6)
445(6.8)
447(7.9)
445(7.1)
456(16)
459(15)
384(6.7)
383(7.0)
382(8.2)
382(8.1)
387(21)
387(19)
373(23)
371(20)
370(27)
371(25)
377(54)
376(50)
6
7
8
9/10
To clarify the nature of the electronic transitions, TD-DFT-
calculations were performed (see computational details)[36]
which were successfully employed on related complexes.[15,37–
39]
In accord with the deconvoluted spectra the calculations
revealed five absorptions with significant intensity in the
recorded spectral region.
Figure 2: UV/Vis spectra of compounds 4-9 recorded in THF at room temperature.
The UV/Vis spectra of complexes 4-10 were recorded in THF at
room temperature and are depicted in Figure 2. The data
extracted from the spectra are listed in Table 2 and are in
accordance with spectra from comparable literature-known
complexes.[8,32] Peak-positions and absorption-coefficients
were obtained by Gaussian deconvolution (R2≥99,9%) of the
recorded spectra (See Figure S2). The spectra (Figure 2) of all
complexes consist of five major absorption bands.
Comparing the spectra of the mononuclear compounds 4-7,
the lowest energy absorption (band #1), a broad band with a
maximum between 519-530 nm, is the only transition that
significantly changes throughout the four spectra. The
wavelength of this absorption increases in the order
4 < 6 < 7 <
5
in increasing order. This increase indicates that the number
t
of Bu-substituents (complexes
on this absorption band than the nature of the opposite
substituent (Br ( ) or BPin ( )). In the spectra of the dinuclear
5 and 7) has a larger influence
4
6
compounds, this band experiences a significant bathochromic
shift and is found at 533 and 534 nm. In the dinuclear
Figure 3 NTOs for the mononuclear compound 7. The first two transitions which
correspond to bands #1 and #2 in the UV/Vis-spectra are represented. Bottom:
The coordinate-system used in the discussion of the electronic transitions. The z-
axis: is perpendicular to the ligand-plane, the y-axis stands between the N,N-
ligands, the x-axis between the N,O-ligands.
complexes
8 and 9/10 the absorption bands #2-#5 are shifted
bathochromically by about 5 nm in comparison to the
mononuclear complexes. This is less than expected from shifts
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On the relevant electronic excitations, NTO-analyses were the coplanar arrangement to be a transition state for the
performed.[40] (Figures 3, 4, S5 and S6). For the discussion of torsion around the C-C bond.
these results, the co-ordinate-system presented in Figure 3 will In the electronic spectrum of the coplanar species obtained by
be used.[41] The lowest energy transition #1 appears to be an TD-DFT calculations (Figure S4), transition #1 is appears at an
MLCT from a dxz orbital at the Ni-atom to the
ligand with a polarization in x-direction.
π
-system of the even lower energy than in the TD-DFT-spectrum of the
unconstrained compound . The electronic transition #1 in the
8
The occupied NTO for transitions #1 and #2 has small dinuclear compounds is thus, strongly dependent of the
coefficients at the 5-tBu groups with opposite sign to the C6- rotation-angle of the biphenylic bond. These results would
ring coefficient, indicating an antibonding interaction between allow tailoring new complexes with respect to optical
the substituents and the C6-ring. This raises the energy of the properties.
occupied frontier orbitals and reduces the band-gap of these
transitions. This is confirmed by the experimental spectra, Electrochemistry
where the absorption band #1 is red-shifted by 11 nm (
) or 4 nm ( and
) on adding one tert-butyl-group.[32]
The NTO-analysis of the most significant transitions in the
dinuclear complex is presented in Figure 4. For absorptions
4 and
The redox-behaviour of all four mononuclear compounds (4-7
)
5
6
7
and the tetra-tert-butyl substituted dinuclear complex (11
)
were investigated. All five substances exhibit two oxidation-
steps in the positive potential range (Table 3) in accord with
reported complexes.[42,43]
8
#1 and #2, transitions from the biphenyl fragment including Ni-
dxz orbitals to salophen moieties is observed. This is in accord
with transitions calculated for the mononuclear complexes.
Due to a small antibonding interaction between the six-
membered rings the highest occupied orbital is shifted
towards higher energies. This results in smaller HOMO-LUMO-
gaps and thus bathochromic shifts of these transitions.
Table 3: Redox-waves of compounds 4-7 and 11 at a scan-rate of 100 mV/s as
referenced to Fc+/Fc. *): No corresponding reduction-signal was detected. **) Since no
corresponding reduction-signal was detected, E1/2 could not be determined. Potentials
are given in mV.
4
5
6
7
11
Eox
1
686
-*
624
512
568
1167*
681
-*
616
545
581
1192
272
219
250
1159
Ered
1
E1/2
1
-**
957
-**
1005
Eox
2
The cyclic voltammogramms (Figure 5) of complexes
5 and 7
show a redox-couple at E1/2=568 mV and 581 mV respectively.
These redox-processes are quasi-reversible according to
standard criteria.[44,45] A second irreversible oxidation step is
detected at Eox=1167 mV and Eox=1192 mV for compounds
and . For compounds and two irreversible oxidation-steps
each were found. The first oxidation of and occur at
5
7
4
6
4
6
potentials of Eox(4.1)=686 mV and Eox(6.1)=681 mV, and the
second steps at Eox(4.2)=957 mV and Eox(6.2)=1005 mV,
respectively.
Figure 4 NTOs for the dinuclear compound 8. The first two
transitions , representing the absorption-bands #1 and #2
observed in the UV/Vis-spectra are depicted.
This thesis that the antibonding character of the occupied
orbital with respect to the biphenylic bond is responsible for
the bathochromic shift of transitions #1 and #2 was further
tested. Therefore, we calculated the structure and electronic
excitation spectra of the putative complex with all phenyl rings
in coplanar arrangement, which should maximize the
antibonding interaction between the phenyl rings. The energy
calculated for this complex is about +6kJ/mol above that of
complex
8. A frequency calculation after the geometry
optimization revealed one negative force constant for the
rotation around the salophen-salophen bond which indicates
Figure 5: CV curves of compounds 4-7 and 11. Potentials are measured vs. Fc+/Fc. The
current of compound 11 was multiplied by the factor 10 to enhance visibility.
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In the cyclic voltammogramm of the dinuclear complex 11
Journal Name
,
complexes by a combination of X-Ray-crystallography, cyclic
also two redox-processes were observed. The first step at E1/2 voltammetry, NMR- and UV/Vis-spectroscopy and was further
= 250 mV is found to be quasi-reversible (see also Figure S15 in evaluated in TD-DFT-calculations. Electronic transitions were
the supplementary material). The second oxidation occurs at a further assigned by NTO-analyses. From these investigations it
potential of Eox=1159 mV and is irreversible. However, due to can be deduced that the tert.-Butyl substituents have a large
the very poor solubility of complex 11, the response was very influence on optical properties and oxidation potentials due to
weak. Since most of the investigated redox-processes are not a shift of high-lying occupied states towards higher energies.
reversible, we have to limit ourselves to comparing the The influence of a Br- as well as pinacolborane substituent is
oxidation-potentials in the following discussion.
rather small for the excitation spectra as well as the oxidation
According to literature, the two above mentioned redox- potentials. However, the substituents have a large influence
processes are located at the ligand.[21,42,43] For the on the reversibility of the redox potentials as well as the
mononuclear compounds, the potential of the first oxidation reactivity of these complexes.
t
depends mainly on the number of Bu-substituents whereas For complex
8
a crystal structure was recorded. It was found
is coplanar in the solid state
the nature of the other substituent (Br or BPin) has only a that the dinuclear complex
8
minor influence. This is to be expected, since the addition of a whereas in the DFT-optimized structure-calculations the
substituent with a +I influence like the tert-butyl group should complex fragments are rotated around the biphenyl axis. The
shift the oxidation to a more negative potential. This finding is evaluation of the electronic spectra revealed that the dinuclear
in accord with the results from the electronic spectra. There, a compounds consist of two electronically weakly coupled
redshift of the first absorption-band for species 5 and 7 is salophen units. The filled metal and π-orbitals on the ligand
attributed to a higher energy of the highest occupied state due appear to be the cause. From DFT-calculations it can be
t
to the second Bu-substituent. The first redox-process found deduced that upon oxidation of the ligand or excitation from a
for the dinuclear compound 11 occurs at the considerably filled ligand π-orbital with antibonding character in respect to
more negative potential of Eox(11.1)=272 mV. Keeping in mind the biphenyl bond the C-C bond strengthens and the electronic
that the oxidation is located on the ligand, it may be assumed coupling of the two complex fragments increase.
that for 11 the biphenyl-part of the molecule gets oxidized. The very successful application of the Suzuki-cross-coupling for
This is in accordance with the electronic spectra, where the the synthesis of sp2-sp2-bonded dinuclear salophen complexes
first electronic transition originates from a highest occupied opens up possibilities for further exploration of this new class
state with a large coefficient on the biphenyl-bridge. DFT- of molecules. Due to the mild conditions of the Suzuki coupling
calculations further reinforce this interpretation: The and the simple synthesis of precursor-complexes, this
optimized structure of 11 has a torsion angle of 28 ° at the synthetic pathway should allow the fabrication of
biphenyl-bond whereas the structure of the hypothetical heterodinuclear complexes or compounds of even higher
cation 11+ is twisted by only 18 °, indicating a considerable nuclearity. Research in this direction is currently carried out by
change in electron density at the biphenyl-unit upon oxidation. our workgroup.
Also, the calculated spin-density of the monocation clearly
indicates that the first oxidation step takes place at the
Experimental Section
General considerations
biphenyl bridge (Figure S7).
All second oxidation-processes in the observed complexes 4-7,
11 are irreversible. Since compounds
4-7 contain rather
If not mentioned otherwise, all reactions were performed
under normal conditions without the exclusion of oxygen or
moisture. Solvents used were of p.a. grade and used as
received. Chemicals were purchased either from Sigma-Aldrich
or MERCK and used as received.
reactive substituents (Br and BPin) it can be assumed that at
potentials as strong as + 1 V chemical reactions take place.
Conclusions
We presented the first method to synthesize dinuclear
salophen-complexes with an unsymmetric substitution pattern
by cross-coupling mononuclear salophen building-blocks. This
method yields a new type of biphenyl-bridged dinuclear
X-ray crystallography was performed on
a Bruker D8
diffractometer with a Bruker Apex 1 camera and an IµS-Mo kα
micro focus source (50 kV, 0.6 mA). Hydrogen-atoms were
constrained at fixed positions and refined using the riding-
model. A disorder at the pinacolborane-group in the structure
of 6 has been treated by a model consisting of two layers of
the carbon-atoms of the pinacolborane-group. Various
restraints and constraints were applied.
salophen complexes. The precursor-complexes
hitherto unknown and to the best of our knowledge,
compounds and are the first examples of boronate-
substituted salophen complexes. Complexes were cross-
coupled yielding the disalophens 11 in good yields.
4-7 were
6
7
4-7
8-
Infrared-spectra were recorded as KBr-discs on a Bruker
Tensor T7 FT-IR-spectrometer.
The complexes were fully characterized including the
determination of the crystal-structures. The unsymmetrical
substitution patterns of the mononuclear complexes allowed
the investigation of substituent-effects (+M, -M, +I, -I) of
different residues on the electronic structure of the salophen
The electronic spectra of solutions of compounds 4-10 in THF
were recorded on a Varian Cary 50 spectrometer. Extinction
coefficients were determined by a serial dilution with five
concentrations. Due to low solubility, no meaningful data
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could be obtained for 11. For the gaussian deconvolution of
the spectra, the Origin 9.0g software-suite was employed.
1H NMR (300 MHz, THF-d8, 25 °C):
δ
NMR - spectroscopy was carried out on a Bruker Avance 400 or 1H, H14), 7.94-7.92 (m, 2H, H9+H12), 7.54 (d, JH3-H5=2.7 Hz,
8.56 (s, 1H, H7), 8.50 (s,
4
3
a Fourier 300 instrument at room temperature with CDCl3 or 1H, H5), 7.36 (dd, JH18-H19=8.7 Hz, JH16-H18=2.6 Hz, 1H, H18),
4
3
DMSO-d6 as solvents and referenced to the solvent-signal. The 7.35 (s, 1H, H16), 7.23 (dd, JH2-H3=9.2 Hz, JH3-H5=2.6 Hz, 1H,
4
3
peaks were assigned according to the numbering-pattern H3), 7.25-7.15 (m, 3H, H10+H11), 6.84 (d, JH18-H19=8.7 Hz, 1H,
presented in Scheme 4.
H19), 6.79 (d, 3JH2-H3=9.2 Hz, 1H, H2), 1.30 (s, 9H, H22).
Cyclic voltammetry was performed using
a δ 156.1 (C14), 155.4 (C7),
BASi C3 13C NMR (75 MHz, THF-d8, 25 °C):
potentiostat. The setup consisted of a 3 mm GC working- 137.8 (C17), 136.7 (C3), 133.4(C18), 134.5 (C5), 128.2 (C16),
electrode, a Pt counter-electrode and an Ag+/Ag reference- 127.3+126.6(C10+C11), 124.1 (C2), 122.9 (C6), 120.6 (C15),
electrode using a Vycore-frit. Where possible, a 1 mM solution 121.7 (C19), 115.1 + 115.3 (C9+C12), 106.3
in DCM of the compound was measured with 0.1 M TBAP as C21), 31.6 (4C, C22).
supporting electrolyte.
(C4), 34.7 (1C,
MS (ESI+, HRMS) m/z 507.0233[M+H]+ (calc: 507.0218).
Synthesis of precursors and complexes
Elemental analysis: found: C 56.7, H 4.17, N 5.51, O 6.30
(calculated: C 56.7, H 4.20, N 5.63, O 6.30).
Synthesis of 5-(4,4,5,5,-tetramethyl-1,3,2-
dioxaborolan-2-yl)salicylaldehyde (3)
Under the exclusion oxygen, 4-bromsalicylaldehyde (10.45 g, Synthesis of N-(3,5-di-tert-butylsalicylidene)-N'-(5-
35.77 mmol), Bis(pinacolato)diboron (13.83 g, 54.46 mmol), bromosalicylidene)phenylene-diaminato nickel(II) (5).
sodium acetate (18.50 g, 136.1 mmol) and PEG600 (200 mL)
This substance was synthesized according to the general
were put into a flask and heated to 70 °C. After degassing the
procedure for the preparation of salophenato-nickel(II)-
mixture for 20 min., tetrakis-triphenylphosphinepalladium(o)
complexes (v.s.). Monoimine
2
:
499 mg, 1.54 mmol,
(1.44 g, 1.25 mmol) was added. The reaction-mixture was then
stirred for 24 h at 70 °C. After extraction with water/ethyl
acetate the raw product was purified by column
chromatography (PE/EE, silica gel) and recrystallization from
nickelacetate-tetrahydrate: 390 mg, 1.57 mmol, 5-bromo
salicylaldehyde: 310 mg, 1.54 mmol. Yield: 721 mg, 1.28 mmol,
83.1 %.
1H NMR (300 MHz, THF-d8, 25 °C):
δ 8.60 (s, 1H, H7), 8.47 (s,
1H, H14), 7.94-7.90 (m, 2H, H9+12), 7.55 (d, JH-H=2.7 Hz, 1H,
hot n-heptane.
A colourless, crystalline product (4.44 g,
4
17.9 mmol, yield: 50 %) was obtained.
H5), 7.39 (d,j 4JH-H=2.6 Hz, 1H, H18), 7.25 (dd, JH-H=9.2 Hz, JH-
4
1H NMR (400 MHz, DMSO-d6, 25 °C):
δ
11.09 (bs, 1H, OH),
H=2.8 Hz, 1H, H3), 7.25-7.16 (m, 3H, H10+H11+ H16), 6.77 (d,
3JH-H=9.1 Hz, H2), 1.45 (s, 9H, H24), 1.31 (s, 9H, H22).
10.27 (s, 1H, H7), 8.00 (d, 1H, 4JH3-H5 = 1.6 Hz, H3), 7.76 (dd, 1H,
3J H6-H5 = 8.3 Hz, 4J H3-H5 = 1.8 Hz, H5), 6.99 (d, 1H, 3J H6-H5 = 8.3 Hz,
H6), 1.28 (s, 12H, H9).
13C NMR (75 MHz, THF-d8, 25 °C):
δ 166.8 (1C, C1), 166.3 (1C,
C20), 155.9 (1C, C14), 154.9 (1C, C7), 142-144 (2C, C8+C13),
141.1 (1C, C19), 137.4 (1C, C3), 137.1 (1C, C17), 135.3 (1C, C5),
130.6 (1C, C18), 128.1 (1C, C10/C11), 127.3 (1C, C16), 127.2
General procedure for the preparation of
mononuclear salophenato-nickel(II)-complexes:
Equimolar amounts of the monoimine
(1 or 2) and (1C, C11/C10), 124.0 (1C, C2), 122.4 (1C, C6), 120.6 (1C, C15),
nickel(II)acetate-tetrahydrate were combined in a flask and 116.0 (1C, C9/C12), 115.8 (1C, C12/C9), 106.0 (1C, C4), 36.3
treated with 2 mL triethylamine. 15 mL of methanol were (1C, C23), 34.7 (1C, C21), 31.4 (4C, C22), 29.7 (4C, C24).
added afterwards. After five minutes of stirring, a solution of
one aliquote of the salicyle aldehyde in
5
mL of MS (ESI+, HRMS) m/z 563.0871[M+H]+ (calc: 563.0844).
tetrahydrofurane was added. The mixture was stirred
overnight, the solvent removed in vacuo, the residue Elemental analysis: found: C 59.6, H 5.18, N 4.97, O 5.67
suspended in methanol and then treated with water. The red (calculated: C 59.7, H 5.20, N 5.01, O 5.67).
precipitate was filtered off and washed with methanol and
diethyl ether and dried in vacuo.
Synthesis of N-(5-tert-butylsalicylidene)-N'-(5-
(4,4,5,5,-tetramethyl-1,3,2-dioxaborolan-2-
yl)salicylidene)phenylenediaminato nickel(II) (6).
Synthesis of N-(5-tert-butylsalicylidene)-N'-(5-
bromosalicylidene)phenylenediaminato nickel(II) (4).
This substance was synthesized according to the general
This substance was synthesized according to the general procedure for the preparation of salophenato-nickel(II)-
procedure for the preparation of salophenato-nickel(II)- complexes (v.s.). Monoimine 411 mg, 1.53 mmol,
complexes (v.s.). Monoimine 985 mg, 3.67 mmol, nickelacetate-tetrahydrate: 390 mg, 1.57 mmol,
1:
1:
nickelacetate-tetrahydrate: 1016 mg, 4.08 mmol, 5-bromo salicylaldehyde
salicylaldehyde: 799 mg, 3.98 mmol. Yield: 1720 mg, mmol, 75.9 %.
3.39 mmol, 92.2 %.
3: 378 mg, 1.52 mmol. Yield: 612 mg, 1.16
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Journal Name
1H NMR (300 MHz, THF-d8, 25 °C):
δ 8.62 (s, 1H, H7), 8.56 (s, solution, a Pinacolborane-precursor-solution and the catalyst-
1H, H14), 8.00-7.94 (m, 2H, H6+H12), 7.92 (d, 1H, JH3- solution, were put into a screw-cap-flask, treated with 2 mL of
4
H5=1.6 Hz, H5), 7.53 (dd, 3JH3-H2=8.7 Hz, JH3-H5=1.7 Hz, H3), 7.37 a 2M solution of potassium-carbonate in water and stirred at
4
3
(s, 1H, H16), 7.35 (dd, 1H, JH18-H19=9.8 Hz, JH16-H18=2.6 Hz, 70 °C for 24 h. Thereafter, the solvent was removed in vacuo,
4
3
H18), 7.24-7.17 (m, 2H, H10+H11), 6.85 (d, 1H, JH18-H19=9.1Hz, the residue suspended in methanol, filtered off, washed with
H19), 6.84 (d, 1H, 3JH2-H3=8.7Hz, H2), 1.31 (s, 12H, H24), 1.29 water, methanol and diethyl-ether and dried in vacuo. The
(s, 9H, H22).
raw-product was then dissolved in pyridine, filtered over celite
and crystallized by addition of n-hexane. Yields:
4+
6: 95 mg,
13C NMR (75 MHz, THF-d8, 25 °C): δ 169.8 (C1), 166.4 (C20), 0.11 mmol, 56 %;
156.2 (C7), 155.8 (C14), 144.3 (C8 C13), 143.7 (C5), 140.6 (C3), 0.13 mmol, 66 %;
137.8 (C17), 134.1 (C18), 129.1 (C16), 127.8+127.5 (C10
121.5+121.1 (C2 C19), 120.2 (C15), 116.1+116.0 (C9
83.9 (C23), 34.5 (C21), 34.1 (C24), 25.1 (C22).
4
+
7: 121 mg, 0.13 mmol, 66 %;
5+6: 119 mg,
+
5+7: 177 mg, 0.183 mmol 93 %.
+
C11), Due to very low solubility of all four coupling-products, only
C12), 1H-NMR-spectra could be obtained.
+
+
8
:
MS (FAB+,HRMS) m/z 555.1983 [M+H]+ (calculated: 555.1965).
1H NMR (300 MHz, DMSO-d6, 25 °C):
δ
8.11-8.05 (m, 4H), 7.83 (d, JH-H=2.5 Hz, 2H), 7.64 (dd, JH-
8.84 (s, 2H), 8.76 (s, 2H),
3
4
4
4
Elemental analysis: found: C 64.8, H 6.00, N 5.01, O 11.3 H=9.0 Hz, JH-H=2.6 Hz, 2H), 7.55 (d, JH-H=2.6 Hz, 2H), 7.43 (dd,
4
3
(calculated: C 64.9, H 5.99, N 5.05, O 11.5).
3JH-H=8.9 Hz, JH-H=2.7 Hz), 7.34-7.31 (m, 4H), 7.00 (d, JH-
H=8.9 Hz), 6.88 (d, 3JH-H=9.0 Hz), 1.34 (s, 18H).
Synthesis of N-(3,5-di-tert-butylsalicylidene)-N'-(5-
(4,4,5,5,-tetramethyl-1,3,2-dioxa-borolan-2-
yl)salicylidene)phenylenediaminato nickel(II) (7).
MS(MALDI+,DHB) m/z 911.3 [M+H]+ (calculated: 911.3), 933.3
[M+Na]+ (calculated: 933.2), 949.3 [M+K]+ (calculated: 949.2).
Simulated isotope patterns match, see Fig. S15.
This substance was synthesized according to the general
procedure for the preparation of salophenato-nickel(II)-
Elemental analysis: found: C 67.0, H 5.04, N 6.44, O 7.66
(calculated: C 67.3, H 4.94, N 6.54, O 7.47).
complexes (v.s.). Monoimine
2:
513 mg, 1.58 mmol,
nickelacetate-tetrahydrate:
398 mg, 1.60 mmol,
9,10
:
salicylaldehyde
mmol, 99.8 %.
3: 383 mg, 1.31 mmol. Yield: 695 mg, 1.31
1H NMR (300 MHz, THF-d8, 25 °C):
δ 8.68 (s, 1H), 8.61 (s, 1H),
8.49 (s, 1H), 8.47 (s, 1H), 8.03-7.97 (m, 2H), 7.93-7.89 (m, 2H),
4
7.61-7.50 (m, 4H), 7.40 (d, JH-H=2.5 Hz), 7.38-7.33 (m, 2H),
1H NMR (300 MHz, THF-d8, 25 °C):
δ 8.67 (s, 1H, H7), 8.52 (s,
1H, H14), 7.95 (d, 1H, JH3-H5=2.0 Hz, H5), 8.00-7.94 (m, 3H,
3
3
4
7.23-7.16 (m, 6H), 6.98 (d, JH-H=8.9 Hz), 6.91 (d, JH-H=8.9 Hz),
6.86 (d, 3JH-H=8.8 Hz), 1.49 (s, 9H), 1.32 (s, 9H), 1.31 (s, 9H).
MS(MALDI+,DHB) m/z 911.3 [M+H]+ (calculated: 911.3), 933.3
[M+Na]+ (calculated: 933.2), 949.3 [M+K]+ (calculated: 949.2).
Simulated isotope patterns match, see Fig. S 15.
3
4
H9+H12), 7.55 (dd, 1H, JH2-H3=8.7 Hz, JH3-H5=1.8 Hz, C3), 7.39
(d, 1H, 4JH16-H18=2.6 Hz, H18), 7.23 (d, 1H, 4JH16-H18=2.6 Hz, H16),
3
7.26-7.20 (m, 2H, H10+H11), 6.84 (d, 1H, JH2-H3=8.7 Hz, H2),
1.46 (s, 9H, H24), 1.30-1.32 (m, 21H, H22, H26),
Elemental analysis: found: C 67.4, H 5.59, N 6.11 (calculated: C
68.5, H 5.52, N 6.14).
13C NMR (75 MHz, THF-D8, 25 °C):
δ 170.2 (C1), 165.6 (C20),
156.0 (C7), 155.8 (C14), 144.5 (C13), 144.0 (C8), 143.7 (C5),
141.3 (C19), 140.3 (C3),137.2 (C17), 130.5 (C18), 127.8 (C16),
127.3 + 127.2 (C10+C11), 122.0 (C4), 121.6 (C6), 121.4 (C2),
120.7 (C15), 115.9 + 115.7 (C9+C12), 83.7 (C25), 36.3 (C23),
34.7 (C21), 31.5 (C24), 29.8 (C26), 25.1 (C22).
11
:
1H NMR (300 MHz, THF-d8, 25 °C):
δ
8.71 (s, 2H), 8.55 (s, 2H),
8.03-7.95 (m, 4H), 7.67 (s, 2H), 7.63-7.59 (m, 2H), 7.40 (s, 2H),
7.25-7.22 (m, 6H), 6.99-6.96 (m, 2H), 1.48 (s, 18H), 1.32 (s,
18H).
MS(MALDI+,DHB) m/z 966.4 [M]+ (calculated: 966.3), 989.3
[M+Na]+ (calculated: 989.3). Simulated isotope patterns
match, see Fig. S 15.
MS (FAB+,HRMS) m/z 611.2582 [M]+ (calculated: 611.2591).
Elemental analysis: found: C 66.81, H 6.76, N 4.58, O 10.5
(calculated: C 67.09, H 6.83, N 4.65, O 10.1).
Elemental analysis: found: C 69.2, H 6.00, N 5.66, O 6.72
(calculated: C 69.5, H 6.04, N 5.79, O 6.61).
Procedure for the Suzuki-Miyaura-cross-coupling:
Computational Details
Stock-solutions of the four precursors were prepared, each in
DFT-calculations were performed using the Gaussian09
software-package[46] with the B3-LYP hybrid-functional and
def2-TZVP basis for all atoms.[47] The geometries were
optimized using crystal structural data as starting-values,
where available. To evaluate whether the optimized
geometries are indeed the global energy-minimum, frequency
15 mL of absolute THF:
4
: 306 mg, 0.602 mmol,
5
: 334 mg,
0.592 mmol,
0.599 mmol.
6
:
330 mg, 0.595 mmol and
7
:
366 mg,
A
stock-solution of the catalyst Pd(PPh3)4
(310 mg, 0.268 mmol in 25 mL of THF) was also prepared. For
the four coupling-reactions, 5 mL each of a Br-precursor-
8 | J. Name., 2012, 00, 1-3
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ARTICLE
analyses were carried out and checked for negative force
constants. In the calculation for the putative coplanar [16]
structure 8Ci, one imaginary frequency at i42 cm-1 is observed
2015, 44, 9732–9735.
M. Bazarnik, B. Bugenhagen, M. Elsebach, E. Sierda, A.
Frank, M. H. Prosenc, R. Wiesendanger, Nano Lett. 2016,
16, 577–582.
and characterizes this state as
a transition state. The
corresponding normal mode represents torsion of the [17]
biphenylic bond.
S. J. Wezenberg, G. Salassa, E. C. Escudero-Adán, J. Benet-
Buchholz, A. W. Kleij, Angew. Chem. Int. Ed. 2010, 50, 713–
716.
Based on the optimized structures TD-DFT-calculations were
performed. Calculation of the first 25 and 30 states for the [18]
mono- and dinuclear compounds proved to sufficiently
reproduce the experimental spectra. A shift in the spectra of [19]
A. C. W. Leung, M. J. MacLachlan, J. Mater. Chem. 2007, 17,
1923–1932.
O. Rotthaus, O. Jarjayes, F. Thomas, C. Philouze, E. Saint-
Aman, J.-L. Pierre, Dalt. Trans. 2007, 889–895.
H. Houjou, M. Ito, K. Araki, Inorg. Chem. 2009, 48, 10703–
10707.
compounds
6 and 7 of ca. 25 nm between the experimental
and calculated transitions is observed. This is attributed to [20]
solvation effects, which weren’t taken into account in the
calculations.
[21]
T. J. Dunn, C. F. Ramogida, C. Simmonds, A. Paterson, E. W.
Y. Wong, L. Chiang, Y. Shimazaki, T. Storr, Inorg. Chem.
2011, 50, 6746–6755.
Acknowledgements
[22]
[23]
A. J. Gallant, J. H. Chong, M. J. MacLachlan, Inorg. Chem.
2006, 45, 5248–5250.
For financial support the DFG (SFB 668-TPA4) is gratefully
acknowledged. The Regionales Rechenzentrum as well as the
Computing Cluster of the Inorganic Chemistry Institute is
acknowledged for generous support and computing time. For
help with cyclic voltammetry measurements we thank Dr.
Daniel Sieh. For generous support and discussions we thank
Prof. Dr. Peter Burger. MHP wishes to thank the DFG funded
Collaborative Research Center 3MET.de (TRR-88) for funding.
R. M. Haak, A. M. Castilla, M. Martinez Belmonte, E. C.
Escudero-Adan, J. Benet-Buchholz, A. W. Kleij, Dalt. Trans.
2011, 40, 3352–3364.
[24]
[25]
A. Suzuki, J. Organomet. Chem. 1999, 576, 147–168.
N. Miyaura, K. Yamada, A. Suzuki, Tetrahedron Lett. 1979,
20, 3437–3440.
[26]
[27]
[28]
[29]
N. Latif, N. Mishriky, F. M. Assad, Recl. Trav. Chim. Pays-Bas
1983, 102, 23–77.
S. Madhupriya, K. P. Elango, Synth. React. Inorganic, Met.
Nano-Metal Chem. 2014, 44, 1104–1114.
J. Lu, Z.-Z. Guan, J.-W. Gao, Z.-H. Zhang, Appl. Organomet.
Chem. 2011, 25, 537–541.
Notes and references
[1]
[2]
R. M. Clarke, T. Storr, Dalt. Trans. 2014, 43, 9380–9391.
J. Y. Yang, D. G. Nocera, J. Am. Chem. Soc. 2007, 129, 8192–
8198.
F. H. Allen, Acta Crystallogr Sect B Struct Sci 2002, 58, 380–
388.
[3]
[4]
[5]
[6]
[7]
A. W. Kleij, M. Kuil, D. M. Tooke, M. Lutz, A. L. Spek, J. N. H.
Reek, Chem. Eur. J. 2005, 11, 4743–4750.
[30]
[31]
A. Hargreaves, S. H. Rizvi, Acta Cryst. 1962, 15, 365–373.
J. Poater, M. Solá, F. M. Bickelhaupt, Chem. Eur. J. 2006,
12, 2889–2895.
A. K. Crane, M. J. MacLachlan, Eur. J. Inorg. Chem. 2011,
2012, 17–30.
[32]
[33]
D. H. Brown, J. H. Morris, G. Oates, W. E. Smith,
Spectrochim. Acta Part A Mol. Spectrosc. 1982, 38, 333–
338.
R. G. Konsler, J. Karl, E. N. Jacobsen, J. Am. Chem. Soc.
1998, 120, 10780–10781.
H. Shimakoshi, W. Ninomiya, Y. Hisaeda, Dalt. Trans. 2001,
13, 1971–1974.
J. W.E. Acree, J. S. Chickos, NIST Chemistry WebBook, NIST
Standard Reference Database Number 69, National
Institute Of Standards And Technology, Gaithersburg MD,
20899, 2011.
O. Rotthaus, O. Jarjayes, C. Philouze, C. P. Del Valle, F.
Thomas, Dalt. Trans. 2009, 1792–1800.
[8]
[9]
M. S. El-Shahawi, W. E. Smith, Analyst 1994, 119, 327–331.
K. Asami, K. Tsukidate, S. Iwatsuki, F. Tani, S. Karasawa, L.
Chiang, T. Storr, F. Thomas, Y. Shimazaki, Inorg. Chem.
2012, 51, 12450–12461.
[34]
[35]
[36]
[37]
P. S. G. E. Staff, UV Atlas of Organic Compounds, Springer
Science + Business Media, 1967.
F. Almasy, H. Laemmel, Helv. Chim. Acta 1950, 33, 2092–
2100.
[10]
[11]
T. Glaser, Chem. Commun. 2011, 47, 116–130.
C. T. Brewer, G. Brewer, G. B. Jameson, P. Kamaras, L. May,
M. Rapta, J. Chem. Soc. Dalt. Trans. 1995, 37–43.
A. Panja, N. Shaikh, P. Gao, Song, Vojtíšek, P. Banerjee,
New J. Chem. 2002, 26, 1025–1028.
R. Bauernschmitt, R. Ahlrichs, Chem. Phys. Lett. 1996, 256,
454–464.
S. Kuck, S.-H. Chang, J.-P. Köckner, M. H. Prosenc, G.
Hoffmann, R. Wiesendanger, ChemPhysChem 2009, 10,
2008–2011.
[12]
[13]
[14]
H. Shimakoshi, S. Hirose, M. Ohba, T. Shiga, H. Okawa, Y.
Hisaeda, Bull. Chem. Soc. Jpn. 2005, 78, 1040–1046.
A. DiLullo, S.-H. Chang, N. Baadji, K. Clark, J.-P. Klöckner,
M.-H. Prosenc, S. Sanvito, R. Wiesendanger, G. Hoffmann,
S.-W. Hla, Nano Lett. 2012, 12, 3174–3179.
J. Oldengott, A. Stammler, H. Bögge, T. Glaser, Dalt. Trans.
[38]
[39]
B. E. C. Bugenhagen, L. Brinn, M. H. Prosenc,
Organometallics 2014, 33, 7015–7018.
A. Choudhary, B. Das, S. Ray, Dalt. Trans. 2015, 44, 3753–
3763.
[40]
[41]
R. L. Martin, J. Chem. Phys. 2003, 118, 4775–4777.
Y. Nishida, S. Kida, Chem. Lett. 1973, 2, 57–62.
[15]
This journal is © The Royal Society of Chemistry 20xx
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ARTICLE
[42]
Journal Name
O. Rotthaus, F. Thomas, O. Jarjayes, C. Philouze, E. Saint-
Aman, J.-L. Pierre, Chem. Eur. J. 2006, 12, 6953–6962.
O. Rotthaus, O. Jarjayes, F. Thomas, C. Philouze, C. Perez
Del Valle, E. Saint-Aman, J.-L. Pierre, Chem. Eur. J. 2006, 12,
2293–2302.
[43]
[44]
M. L. Olmstead, R. S. Nicholson, Anal. Chem. 1966, 38,
150–151.
[45]
[46]
R. S. Nicholson, Anal. Chem. 1966, 38, 1406–1406.
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, et al., n.d.
[47]
F. Weigend, R. Ahlrichs, Phys. Chem. Chem. Phys. 2005, 7,
3297–3305.
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DOI: 10.1039/C5DT04612B
O
B
Br
O
+
N
N
Pd(PPh3)4
N
O
N
O
N
O
N
O
O
Ni
O
Ni
O
N
THF, K2CO3
70 °C, 24 h
Ni
N
Ni
R2
R1
O
8:
R1=R2= 5'-tBu
9/10: R1=3,5-ditBu, R2= 5'-tBu
11: R1=R2=3,5-ditBu
R1
R2