Cyclometalated Ruthenium(II) NHC Complexes with Imidazo[1,5-a]pyridine-Based (C^C*) Ligands – Synthesis and Characterization

Article abstract of DOI:10.1002/ejic.201900108

We present the synthesis and characterization of cyclometalated ruthenium(II) NHC complexes with phenyl-substituted imidazo[1,5-a]pyridine C^{^}C* ligands. The corresponding p-cymene complexes can be reacted with bipyridine to form bisheteroleptic ruthenium(II) dyes. The compounds have been characterized by one- and two-dimensional ¹H/¹³C NMR spectroscopy, elemental analysis, cyclic voltammetry, infrared spectroscopy, as well as solid-state structure (X-ray) analysis.

Full text of DOI:10.1002/ejic.201900108

DOI: 10.1002/ejic.201900108
Full Paper
Bridging Ligands
Cyclometalated Ruthenium(II) NHC Complexes with
^
Imidazo[1,5-a]pyridine-Based (C C*) Ligands – Synthesis and
Characterization
David Schleicher, Alexander Tronnier, Johannes Soellner, and Thomas Strassner*
[a]
[a]
[a]
[a]
1
13
Abstract: We present the synthesis and characterization of have been characterized by one- and two-dimensional H/ C
cyclometalated ruthenium(II) NHC complexes with phenyl- NMR spectroscopy, elemental analysis, cyclic voltammetry,
^
substituted imidazo[1,5-a]pyridine C C* ligands. The corre- infrared spectroscopy, as well as solid-state structure (X-ray)
sponding p-cymene complexes can be reacted with bipyridine analysis.
to form bisheteroleptic ruthenium(II) dyes. The compounds
Introduction
Results and Discussion
Synthesis and Characterization
Over the past 20 years N-heterocyclic carbenes (NHCs) have
been extensively studied and used as ligands in transition metal
complexes for catalytic, photophysical, and biological applica-
tions. Their main advantages over “classical” neutral ligands like
phosphanes or amines are their strong σ-donor character and
their additional ability for π-orbital interactions which lead to
The synthesis of all compounds in this study starts with the
condensation of a (substituted) aniline with 2-pyridinecarboxy-
aldehyde to yield the respective imidazo[1,5-a]pyridinium salts,
as we already discussed in detail in our previous study on plati-
[9]
num complexes. This method, which follows a procedure
[
1]
very stable transition metal complexes. The electron density
on the metal center can not only be modified via different sub-
stituents on the NHC ligand, but also by the structure of the
[5]
published by Hutt and Aron in 2011 features mild reaction
conditions at room temperature and convenient workup proce-
dures as well as a broad substrate scope. In general, the ob-
tained chloride salts are hygroscopic and contain small
amounts of water even after prolonged drying, while the tetra-
fluoroborate salts can be obtained solvent-free.
[
2]
carbene heterocycle itself. Moreover, in recent years NHC con-
[
3]
cepts beyond “simple” heterocycles, e.g. functionalized NHCs,
or even acyclic carbenes have been studied intensively.
[
4]
A rather unusual precursor for imidazolium-based NHC li-
gands are imidazo[1,5-a]pyridinium salts, whose 2-phenyl-sub-
stituted derivatives can be readily obtained by condensation
reactions under mild conditions from commercially available
The ligand precursors are then reacted with the [Ru(p-cym-
[11]
ene)Cl ] dimer following our one-pot transmetalation route
2
2
from the corresponding silver carbenes (see Scheme 1). Trans-
metalation as well as cyclometalation proceed at room temper-
ature within the course of several days. A higher reaction tem-
perature generally leads to more decomposition (as can be ob-
served by a rapid darkening of the reaction mixture) and does
not improve the overall yields. For workup the mixture is fil-
[
5]
starting materials, as described by Hutt and Aron. Until now
this NHC motif has been used in transition metal complexes
[
6]
either as a monodentate ligand or as a chelating ligand via
[
7]
oxygen or nitrogen atoms. However, the only examples of its
^
use as C C* cyclometalating NHC ligand have been reported
III
[8]
for Ir complexes from the groups of Mashima and Gong and
II
[9]
for Pt complexes from our group. To the best of our knowl-
edge, no examples of ruthenium complexes with imidazo-
[
1,5-a]-pyridine-NHC ligands can be found in the literature,
which is why we were –following our investigation of related
[
10]
phenylimidazol-based complexes
thesis, reactivity, and properties.
– interested in their syn-
[
a] Physikalische Organische Chemie, Technische Universität Dresden
1069 Dresden, Germany
0
E-mail: thomas.strassner@chemie.tu-dresden.de
http://chm.tu-dresden.de/oc3/eng/index.shtml
Scheme 1. Synthesis of cyclometalated Ru NHC complexes via transmetala-
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.201900108.
tion from silver carbene complexes. Reagents and conditions: (i) 0.5 [Ru(p-
cymene)Cl ] , 1 eq. Ag O, DCM, r.t., 1–5 d.
2 2 2
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Full Paper
tered through diatomaceous earth, evaporated, and dissolved a dark blue over the course of several days in air. This observa-
in small amounts of tetrahydrofuran (THF). Following filtration tion, which has already been described by Albrecht[12] for
through basic aluminium oxide the pure complexes slowly crys- similar complexes, resembles our findings for the same type of
^
tallize after addition of n-pentane. The yields range from ap- complexes bearing substituted phenylimidazoles as C C* li-
prox. 30 to 60 % with the exception of complex 6, which we gands.[
11]
were only able to obtain in a very poor yield of 4 %. It should
We were able to obtain yellow to orange single crystals from
be noted that no formation of a 4-membered metallacycle by all the p-cymene complexes 1–6. Their solid-state structures are
cyclometalation to the pyridine moiety was observed in any of shown in Figure 1. In all complexes the ruthenium atom is sur-
6
^
the reactions.
rounded by the η -ligand, the C C* ligand, and one chloride in
The resulting cyclometalated ruthenium(II) NHC complexes a pseudo-tetrahedral geometry. Bond lengths and angles in
are yellow to orange crystalline air-stable solids, which are read- these complexes (see Table 1) are in general quite similar to our
[
10,11]
ily soluble in organic solvents such as dichloromethane (DCM), previously reported phenylimidazol-analogues.
Complex 6
tetrahydrofuran, acetone, methanol, ethanol, acetonitrile with two CF -groups in 3,5-position of the cyclometalated
3
(
(
MeCN), dimethyl formamide (DMF), and dimethyl sulfoxide phenyl ring shows some structural differences. Here the dis-
DMSO). Their solutions slowly turn green, which changes into tance between the metal center and the anionic carbon atom
is elongated by 0.02 Å, which can be explained by the reduced
electron density in this phenyl ring as well as a slight steric
hindrance caused by the CF group in ortho position to the
3
cyclometalation (3-position). Furthermore this complex shows
the shortest metal-carbene bond length with 2.00 Å. The
slightly higher distance to the p-cymene ring is also caused by
the steric repulsion of the CF -group in 3-position.
3
Bipyridyl Complexes
Simultaneously with the group of Nazeeruddin[13] we recently
introduced the synthesis of bisheteroleptic ruthenium(II) dyes
^
starting from the corresponding p-cymene C C* complexes into
[
10]
the literature.
In perfect analogy, the conversion to the bisheteroleptic bi-
pyridyl complexes bearing imidazo[1,5-a]pyridines follows our
published route via reaction with a slight excess of 2,2′-bipyr-
idine (bpy) in DMSO at elevated temperatures and subsequent
anion exchange as shown in Scheme 2.
The deep violet hexafluorophosphate salts are readily solu-
ble in polar organic solvents like MeCN, acetone, alcohols, DCM,
DMF, DMSO and are stable under ambient conditions. Their so-
lutions, regardless of the solvent, show no signs of decomposi-
tion over the course of several weeks.
We were able to obtain single crystals of complexes 7, 10,
and 11 by slow evaporation from an acetone/water solution.
Their solid-state structures are shown in Figure 2. They feature
an only slightly distorted octahedral structure with an almost
^
planar C C* ligand. By comparing the bond lengths from the
metal center to the nitrogen atoms, a trans-influence of the
strong carbon donors can be seen, which causes an elongation
of the opposing Ru–N bonds (N3 and N5) by 0.05–0.06 Å
Figure 1. ORTEP of 1–6 in the solid state. Thermal ellipsoids are drawn at the
5
0 % probability level; H atoms are omitted for clarity.
Table 1. Selected bond lengths [Å], angles and dihedral angles [°] of complexes 1–6.
1
2
3
4
5
6
Ru(1)–Cl(1)
Ru(1)–C(1)
Ru(1)–C(9)
Ru(1)–Centroid
C(1)–Ru(1)–C(9)
C(1)–N(1)–C(8)–C(9)
2.4114(9)
2.024(3)
2.081(5)
1.732
76.59(16)
–3.9(4)
9.8
2.4192(9)
2.022(3)
2.060(4)
1.729
76.09(14)
1.7(4)
2.4304(4)
2.0159(15)
2.0695(15)
1.739
76.64(6)
–4.6(2)
2.4095(12)
2.015(4)
2.067(4)
1.731
76.64(15)
–1.3(5)
9.8
2.4092(14)
2.025(5)
2.077(4)
1.727
77.16(17)
0.4(3)
2.4061(12)
2.003(4)
2.100(4)
1.744
77.33(14)
1.6(4)
[
14]
C* yaw-distortion
9.1
9.1
10.7
9.7
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(
Table 2). These findings are in agreement with our previously
[
10]
published structures as well as non-cyclometalated NHC ana-
logues
[
15]
[16]
and cyclometalated N-bound analogues.
Interest-
ingly Nazeeruddin et al. found significantly elongated distances
to the carbene (2.05–2.09 Å) and cyclometalated (2.11–2.17 Å)
[
13]
carbon atoms.
Spectroscopic and Electrochemical Properties
The bisheteroleptic complexes 7–11 show a strong absorption
in the visible part of the spectrum up to approx. 650 nm (Fig-
ure 3). It is noticeable that the different substituents –with the
exception of the nitro group in compound 10 (slightly hypso-
chromic) – have only a small effect on the position and intensity
of the absorption bands.
Scheme 2. Synthesis of the bisheteroleptic cyclometalated Ru NHC complexes
bearing two bipyridine ligands. Reagents and conditions: (ii) bpy (2.2 equiv.),
DMSO, 140 °C, 20 h. (iii) H O, NH PF .
2 4 6
Figure 3. UV/Vis spectra of complexes 7–11 and 7Im (previously published[10]
as 0.1 m solutions in acetonitrile.
)
M
Comparing the unsubstituted complex 7 with its phenylimid-
[
10]
azole based congener 7Im,
the imidazopyridine ligand pro-
vides a more intense absorption in the 400–450 nm area, lead-
ing to a “smoother” absorption profile between 300 and
5
50 nm.
This observation is in agreement with time-dependent (TD)
DFT calculations (PBE0, def2-SVPD) of the absorption spectra,
as shown in Figure 4. Compound 7 shows two prominent transi-
tions around 425 nm, originating from MLCT transitions
Figure 2. ORTEP of 7 (only Δ isomer), 10 (Λ isomer left side, Δ isomer right
side), and 11 (only Λ isomer) in the solid state. Thermal ellipsoids are drawn
at the 50 % probability level; H atoms, the anions (hexafluorophosphate), and
solvent molecules (one acetone per structure) are omitted for clarity.
(HOMO→LUMO+3 and HOMO→LUMO+4). For compound 7Im
only one transition around 425 nm is predicted which also cor-
responds to an MLCT transition (HOMO→LUMO+2).
Additionally we performed cyclic voltammetry measure-
ments for complexes 7–11. The observed oxidation and reduc-
tion waves are given in Table 3; graphical representations can
be found in the Supporting Information. In general, the
Table 2. Selected bond lengths [Å], angles and dihedral angles [°] of com-
plexes 7, 10, 11.
10[a]
7
11
II
III
Ru /Ru oxidation bands are in the expected range between
Ru(1)–C(1)
Ru(1)–C(9)
Ru(1)–N(3)
Ru(1)–C(1)
Ru(1)–N(4)
Ru(1)–N(5)
Ru(1)–N(6)
C(1)–Ru(1)–C(9)
2.018(2)
2.057(2)
2.002(4), 2.025(5)
2.061(5), 2.064(4)
2.099(4), 2.107(3)
2.002(4), 2.025(5)
2.061(4), 2.045(3)
2.136(3), 2.138(4)
2.061(4), 2.071(4)
78.42(17), 78.45(17)
12.02, 11.49
2.014(9)
2.069(9)
2.110(7)
2.014(9)
2.051(7)
2.129(8)
2.056(8)
78.0(3)
0
.6 eV and 0.7 eV vs. NHE, comparable to previously published
[
10,13]
2.0892(18)
2.018(2)
2.0625(18)
2.1268(18)
2.0687(18)
78.25(8)
imidazolium-based congeners
phenylpyridine complexes.
as well as cyclometalated
However, the measure-
[
16a,16b,17]
ments revealed two remarkable results. First, the substituents
on the cyclometalating phenyl ring seem to have no systematic
effect whatsoever on the oxidation potential. This is particularly
evident when comparing complex 7 (no substituent), 8 (meth-
oxy substituent), and 10 (electron-withdrawing nitro substitu-
ent), which basically show the same oxidation potential. Sec-
[14]
C* yaw-distortion
11.45
10.83
[
a] Two independent molecules (Λ and Δ isomer) in unit cell; first values for
Λ, second values for Δ.
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ligand motif is used for ruthenium, which is quite surprising
given the convenient experimental accessibility of the ligand
precursors and their wide range of available substitution pat-
terns. Starting from the corresponding p-cymene chloro com-
6
plexes we used the displacement of the η -ligand and the
chloro anion to form bipyridyl dyes. Their electrochemical prop-
erties and absorption profiles were found to be quite similar to
the corresponding phenylimidazole-based bisheteroleptic dyes.
Experimental Section
General: The reactions throughout this study were carried out em-
ploying standard Schlenk techniques. Solvents were of high purity
(> 99.5 %); acetonitrile was dried in an MBraun Solvent Purification
System prior to use. Ruthenium(III)-chloride was purchased from
Pressure Chemicals Co. and used as received. The dichloro(p-cym-
ene)ruthenium(II) dimer was prepared according to the literature.[
All other chemicals are commercially available from common sup-
pliers and were used without further purification. The synthesis of
19]
[
9] 1
13
imidazopyridinium salts b, c, f is described elsewhere. H and
C
NMR spectra were recorded on a Bruker Avance 300 P, Bruker DRX
1
13
5
00 P or a Bruker ACS 600 spectrometer at 298 K. H and C spectra
1
were referenced internally using the resonances of the solvent ( H:
.26, 13C: 77.0 for CDCl ; H: 2.50, C: 39.43 for [D ]DMSO; H: 1.94,
1
13
1
7
3
6
13
C: 1.32 for CD CN). Shifts δ are given in ppm downfield from
3
tetramethylsilane, coupling constants J in Hz. 2D NMR methods
1
13
(
COSY, NOESY, HSQC, HMBC) were employed for the H and
C
^
signal assignment of the C C* ligand. Elemental analyses were per-
formed on a Eurovector Hekatech EA3000 by the microanalytical
laboratory of our institute. Melting points were determined on a
non-calibrated hot stage microscope. UV/Vis spectra were recorded
Figure 4. TD DFT calculated transitions (red columns) and convoluted absorp-
tion (orange lines) of complexes 7 (above) and 7Im (below) as well as the
experimental absorption spectra (blue hashed lines).
on a Perkin Elmer Lambda 25 as 0.1 m
M solutions in acetonitrile.
ond, all oxidation processes were recorded as (quasi-)irreversi- Cyclic Voltammetry: Electrochemical measurements were carried
out with a BioLogic SP-150 potentiostat in degassed, dry aceto-
nitrile using a Pt counter electrode, a glassy carbon working elec-
trode and a Ag/Ag pseudoreference electrode. All complexes were
ble, which is in contrast to the phenylpyridine complexes and
resembles orthometalated aminocarbenes reported by Yam and
+
[
18]
co-workers.
Towards negative potentials all complexes un-
measured as 5 mM solutions with the addition of 0.1 M N(nBu) ClO
4 4
dergo two distinct reversible reduction processes, which can be
attributed to one-electron reductions of the bipyridyl ligands.
For complex 10 the first reduction wave is shifted by 0.3 eV
and an additional irreversible reduction band is observed, origi-
nating from the “non-innocent” redox active nitro substituent.
as supporting electrolyte at a sweep rate of 50 mV/s. Every meas-
+
urement was internally referenced against the Fc/Fc redox couple,
+
[20]
and potentials were converted to NHE via Fc/Fc vs. NHE = 0.63 V.
For visualization the EC-Lab software V11.01 and Origin 2016 were
used.
DFT Calculations: All calculations were performed using the den-
sity functional hybrid model PBE0 within the Gaussian16 (Rev.
Table 3. Electrochemical properties of complexes 7–11.
[
21]
[22]
E
E
1/2[V][a] (ΔE [mV]) vs. NHE
A.03) package. Atoms were described by the Karlsruhe def2-SVPD
II
III
red2
E
red1
Eox (Ru /Ru )
[23]
[23,24]
basis set (including an ECP
for Ru). No symmetry or internal
[
[
[
b]
b]
b]
7
8
9
1
1
–1.61 (76)
–1.62 (70)
–1.58 (82)
–1.64 (65)
–1.59 (71)
–1.37 (76)
–1.37 (66)
–1.35 (60)
–1.04 (74)
–1.35 (65)
0.63
0.63
0.68
0.62
0.68
coordinate constraints were applied during optimizations. All re-
ported structures were verified as true minima by the absence of
imaginary eigenvalues in the vibrational frequency analysis. Ap-
proximate free energies (ΔG) were obtained through thermochemi-
cal analysis, using the thermal correction to Gibbs free energy as
reported by Gaussian16. This takes into account zero-point effects,
thermal enthalpy corrections, and entropy. TD DFT calculations in-
corporated a solvent model (CPCM, solvent = acetonitrile). UV spec-
[
c]
[b]
b]
0
1
[
[
a] Recorded in MeCN (see exp. section for details) with Fc/Fc+ as internal
standard. [b] (Quasi-)irreversible. [c] Occurs after a large irreversible reduction
band for the NO group.
2
[
25]
tra were generated by GaussView 6,
using convoluted Gaussian
bands with a half-width at half height value of 0.3 eV. For visualiza-
[
26]
[27]
tion CYLview,
and Avogadro
were used.
Conclusions
X-ray Crystallography: Preliminary examination and data collec-
tion for single crystals of compounds 1, 2, 4–6 and 11 were carried
A series of substituted phenyl-imidazo[1,5-a]pyridines was in-
^
corporated as C C* ligands in ruthenium(II) complexes. To the out on an area detecting system (Kappa-CCD; Nonius, FR590) using
best of our knowledge, these are the first examples where this graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å) with an
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1
Oxford Cryosystems cooling system at the window of a sealed fine-
focus X-ray tube. The reflections were integrated. Raw data were 12.08 (dd, J = 1.9, 0.8 Hz, 1H, NCHN), 9.42 (dd, J = 7.2, 1.1 Hz, 1H,
corrected for Lorentz, polarization, decay and absorption effects. C H), 8.09 (dd, J = 1.9, 0.9 Hz, 1H, C H), 7.88–7.80 (m, 2H, C H),
line product. (1.5 g, 33 %; m.p. 95 °C). H NMR (300 MHz, CDCl ) δ =
3
ar
ar
ar
[
28]
The absorption correction was applied using SADABS.
merging, the independent reflections were used for all calculations.
After
7.70 (dd, J = 9.4, 1.0 Hz, 1H, C H), 7.66–7.52 (m, 3H, C H), 7.30–7.18
ar ar
1
3
(m, 1H, C H), 7.06 (td, J = 7.0, 1.1 Hz, 1H, C H). C NMR (75 MHz,
CDCl ) δ = 134.8 (C ), 131.1 (C H), 130.9 (Cph(o/m)H), 130.6 (Cipso),
ar
ar
[
29]
The structure was solved by a combination of direct methods
3 ipso ar
[30]
and difference Fourier syntheses.
All non-hydrogen atom posi- 127.0 (C H), 126.1 (C H), 125.9 (C H), 122.6 (C
H), 117.9 (C H),
ar
ar
ar
ar
ph(o/m)
tions were refined with anisotropic displacement parameters. 117.6 (C H), 110.3 (C H). Anal. Calcd for C H ClN ·0.25H O (M =
ar
ar
13 11
2
2
Hydrogen atoms were placed in ideal positions using the SHELXL
riding model. Full-matrix least-squares refinements were carried out
233.66 g/mol): C: 66.39, H: 4.93, N: 11.91; found C: 66.23, H: 4.77, N:
12.05 %.
by minimizing σw(Fo2 – F ) with the SHELXL-97 weighting scheme
2 2
c
2
-(4-Nitrophenyl)-2H-imidazo[1,5-a]pyridinium Chloride (d): 5.24 g
and stopped at shift/err less than 0.001. Details of the structure
determinations are given in the Supporting Information. Neutral-
atom scattering factors for all atoms and anomalous dispersion cor-
rections for the non-hydrogen atoms were taken from International
Tables for Crystallography.[ All calculations were performed with
(30 mmol) of 4-nitroanilinium hydrochloride, 3.21 g (2.87 mL,
3
4
0 mmol) of 2-pyridinecarboxaldehyde and 3.65 g (3.37 mL,
5 mmol) of a 37 wt.-% aqueous solution of formaldehyde were
dissolved in 40 mL of ethanol and stirred at room temperature for
31]
2
1
8 h and then heated to 65 °C for another 20 h. After this period,
mL of concentrated hydrochloric acid was added and the mixture
the programs COLLECT,[
32]
DIRAX,
[33]
EVALCCD,
[34]
SIR92,
package.
[29a]
SIR97,[
29b]
SADABS,[28] PLATON[35] and the SHELXL-97
[30,36]
was stirred at room temperature for another 10 d. The yellow-green
Preliminary examination and data collection for single crystals of precipitate was filtered, washed with ethanol and diethyl ether and
compounds 3, 7, and 10 were carried out on a Bruker D8 VENTURE
KAPPA goniometer, PHOTON detector) single crystal-diffractometer
dried in vacuo. (6.3 g, 74 %; dec > 245 °C). 1H NMR (300 MHz,
[D ]DMSO) δ = 10.63 (dd, J = 2.0, 0.8 Hz, 1H, NCHN), 8.90 (dd, J =
6
(
equipped with an Oxford Cryosystem (Cryostream 800) cooling sys- 1.9, 1.0 Hz, 1H, C H), 8.65 (dd, J = 7.0, 1.2 Hz, 1H, C H), 8.62–8.56
ar
ar
tem at the window of a sealed X-ray tube using monochromated
(m, 2H, C H), 8.26–8.18 (m, 2H, C H), 7.96 (dd, J = 9.2, 1.1 Hz, 1H,
C H), 7.42–7.26 (m, 2H, C H). C NMR (75 MHz, [D ]DMSO) δ =
ar ar 6
ar ar
13
Mo-K radiation (λ = 0.71073 Å) (Incoatec IμS3.0 microfocus source
α
equipped with multilayer optics). Intensity data were extracted us- 148.2 (Cipso), 139.6 (Cipso), 129.9 (Cipso), 126.7 (C H), 125.7 (CphH),
ar
ing the APEX3 suite[ including the SAINT software package.
37]
[38]
125.5 (C H), 124.3 (C H), 118.6 (C H), 118.4 (C H), 112.3 (C H).
ar ph ar ar ar
The reflections were merged and corrected from Lorentz, polariza-
tion and decay effects and absorption correction was applied based
[one (C H) not detected]. Anal. Calcd for C H ClN O ·0.5H O (M =
ar 13 10 3 2 2
284.05 g/mol): C: 54.84, H: 3.89, N: 14.76; found C: 54.78, H: 3.94, N:
14.72 %.
[39]
on multiple scans. The structure was solved by a combination of
dual space[ and direct methods with the aid of difference Fourier
40]
2
-[4-(Ethoxycarbonyl)phenyl]-2H-imidazo[1,5-a]pyridinium
Chloride
[
41]
synthesis and were refined against all data using SHELXTL-XTMP
(e). 5.24 g (30 mmol) of 4-nitroanilinium hydrochloride, 3.21 g
(2.87 mL, 30 mmol) of 2-pyridinecarboxaldehyde and 3.65 g
(3.37 mL, 45 mmol) of a 37 wt.-% aqueous solution of formaldehyde
Hydrogen atoms were assigned to ideal positions using the
SHELXTL-XTMP riding model. All non-hydrogen atoms were refined
with anisotropic displacement parameters. Full-matrix least-squares
were dissolved in 40 mL of ethanol and stirred at room temperature
for 48 h. After this period, 1 mL of concentrated hydrochloric acid
was added and the mixture was stirred for another 10 d. The white
precipitate was filtered, washed with diethyl ether and dried in
vacuo. The filtrate was concentrated to half its volume to obtain a
2
2 2
refinements were carried out by minimizing Σw(Fo – F ) with the
c
SHELXTL-XTMP weighting scheme Neutral-atom scattering factors
for all atoms and anomalous dispersion corrections for the non-
hydrogen atoms were taken from the International Tables for Crys-
[
31]
tallography.
All calculations were performed with the APEX3
second fraction of the colorless product. (6.8 g, 72 %; dec > 240 °C).
suite[ including the SAINT software package,
37]
[38]
the SHELX pro-
1
H NMR (300 MHz, [D ]DMSO) δ = 10.50 (s, 1H, NCHN), 8.85 (s, 1H,
6
gram package,[ and PLATON.
30]
[35]
C H), 8.61 (dd, J = 7.0, 1.2 Hz, 1H, C H), 8.32–8.24 (m, 2H, C H),
ar
ar
ar
Images of all solid-state structures were generated with ORTEP3.[42]
8.08 (d, J = 8.7 Hz, 2H, C H), 7.94 (dd, J = 9.3, 1.1 Hz, 1H, C H),
a
r
a
r
7
7
.42–7.23 (m, 2H, C H), 4.39 (q, J = 7.1 Hz, 2H, CH CH ), 1.37 (t, J =
ar 2 3
Synthesis of the Ligand Precursors: The synthesis of the ligand
precursors generally started from the corresponding anilines, which
were converted into their hydrochloride salts by slowly adding an
excess of concentrated hydrochloric acid to an ice-cooled solution
of the amine in ethanol. The precipitating pyridinium hydrochloride
salts were filtered, washed thoroughly with diethyl ether and dried
in vacuo. The colorless crystalline products were used in further
synthesis without characterization.
13
.1 Hz, 3H, CH CH ). C NMR (75 MHz, [D ]DMSO) δ = 164.6
2
3
6
(
(
(
COOEt), 138.4 (Cipso), 131.5 (Cipso), 131.1 (CphH), 129.9 (Cipso), 126.2
C H), 125.4 (C H), 124.3 (C H), 123.2 (C H), 118.5 (C H), 118.4
C H), 112.1 (C H), 61.4 (CH CH ), 14.1 (CH CH ). Anal. Calcd for
ar
ar
ar
ph
ar
ar
ar
2
3
2
3
C H ClN O ·0.6H O (M = 312.89 g/mol): C: 61.29, H: 5.21, N: 8.93;
16
15
2
2
2
found C: 61.20, H: 5.29, N: 8.96 %.
Synthesis of p-Cymene Complexes
NMR numbering scheme
2
-Phenyl-2H-imidazo[1,5-a]pyridinium chloride (a). 2.59 g (20 mmol)
of anilinium hydrochloride, 2.14 g (1.91 mL, 20 mmol) of 2-pyridine-
carboxaldehyde and 2.59 g (2.25 mL, 30 mmol) of a 37 wt.-% aque-
ous solution of formaldehyde were dissolved in 40 mL of ethanol
and stirred at room temperature for 40 h. The solution was concen-
trated to approx. 1/3 of its volume and an excess of diethyl ether
was added to complete the precipitation. The precipitate was fil-
tered, washed with diethyl ether and dried in vacuo. The crude off-
white product (> 4 g) was afterwards dissolved in 50 mL of aceto-
nitrile, stirred over Na SO for 2 h at 60 °C and filtered through
2
4
2
3
6
active charcoal. The filtrate was concentrated to approx. half its vol-
Chloro[2-(phenyl-κC )imidazolino[1,5-a]pyridin-3-ylidene-κC ][η -1-
ume and diethyl ether was added to precipitate the white crystal- methyl-4-(1-methylethyl)benzene]ruthenium(II) (1). 115 mg
Eur. J. Inorg. Chem. 0000, 0–0
www.eurjic.org
5
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
(
1
0.5 mmol) of 2-phenyl-2H-imidazo[1,5-a]pyridinium chloride a,
CH Cl were added. The resulting deep red suspension was stirred
2
2
6
53 mg (0.25 mmol) of [RuCl (η -p-cymene)] and 117 mg
at room temperature under exclusion of light for 5 d and the dark
solution was evaporated to dryness. The dark solid was subjected
to column chromatography (SiO ; CH Cl /MeOH, 20:1; R = 0.95).
2
2
(0.5 mmol) of Ag O were placed in a Schlenk tube and 15 mL of
2
CH Cl were added. The resulting deep red suspension was stirred
2
2
2
2
2
f
at room temperature under exclusion of light for 3 d and after
evaporation the crude product was purified by column chromatog-
raphy (SiO ; CH Cl /MeOH, 10:1; R = 0.9). The product fraction was
dried, dissolved in small amounts (≈ 10 mL) of THF and filtered
through basic alumina. The yellow product was slowly precipitated
The product fraction (broad yellow band) was, after evaporation in
vacuo, dissolved in ≈ 25 mL of THF and filtered through basic alu-
mina. The product is then precipitated by slow addition of pentane
2
2
2
f
1
(≈ 50 mL). (580 mg, 36 %; dec > 180 °C). H NMR (600 MHz, CDCl )
3
δ = 8.52 (dd, J = 7.3, 1.1 Hz, 1H, C1H), 8.31 (d, J = 1.6 Hz, 1H, C8H),
7.59 (s, 1H, C5H), 7.20 (dd, J = 9.3, 1.3 Hz 1H, C4H), 7.08–7.03 (m,
2H, C6H + C7H), 6.77 (ddd, J = 9.3, 6.4, 1.0 Hz, 1H, C3H), 6.62 (ddd,
by slow addition of n-pentane to the filtrate. (98 mg, 42 %;
1
dec > 220 °C). H NMR (500 MHz, CDCl ) δ = 8.59 (dd, J = 7.3, 1.1 Hz,
3
1
7
6
1
1
H, C1H), 8.23 (d, J = 8.7 Hz, 1H, C8H), 7.67 (d, J = 0.9 Hz, 1H, C5H),
.31–7.27 (m, 2H, C4H + C6H), 7.07–7.01 (m, 2H, CarHpara + C7H), 5.64–5.59 [m, 2H, C H(cym)], 5.56 [dd, J = 6.0, 1.1 Hz, 1H, C H(cym)],
.79 (ddd, J = 9.3, 6.3, 0.9 Hz, 1H, C3H), 6.62 (ddd, J = 7.3, 6.3, 1.1 Hz,
J = 7.4, 6.3, 1.2 Hz, 1H, C2H), 5.68 [dd, J = 6.0, 1.1 Hz, 1H, C H(cym)],
ar
ar
ar
2.11 [s, 3H, C CH (cym)], 2.07 [hept, J = 6.9 Hz, 1H, CH(CH ) ], 0.79
ar 3 3 2
1
3
H, C2H), 5.67 [dd, J = 5.8, 1.3 Hz, 1H, C H(cym)], 5.64 [dd, J = 6.0,
[d, J = 6.9 Hz, 3H, CH(CH ) ], 0.66 [d, J = 6.9 Hz, 3H, CH(CH ) ].
C
ar
3 2
3 2
.2 Hz, 1H, C H(cym)], 5.58 [dd, J = 6.0, 1.3 Hz, 1H, C H(cym)], 5.53 NMR (151 MHz, CDCl ) δ = 178.5 (C
), 167.9 (CRu), 144.3 (C N),
ar
ar
3
carbene
ar
[
dd, J = 5.9, 1.2 Hz, 1H, C H(cym)], 2.16–2.10 [m, 1H, CH(CH ) ], 2.09
143.3 (C8H), 132.1 (Cipso,py), 126.8 (C1H), 125.5 (C7H), 121.8 (C3H),
118.9 (CarBr), 118.7 (C4H), 114.0 (C6H), 113.4 (C2H), 106.6
ar
3 2
[s, 3H, C CH (cym)], 0.82 [d, J = 6.9 Hz, 3H, CH(CH ) ], 0.69 [d, J =
ar 3 3 2
13
6
1
1
1
.9 Hz, 3H, CH(CH ) ]. C NMR (126 MHz, CDCl ) δ = 179.3 (Ccarbene), [C CH (cym)], 104.8 (C5H), 99.3 [C iPr(cym)], 92.6 [C H(cym)], 89.6
3 2 3 ar 3 ar ar
64.9 (CRu), 145.2 (C N), 141.8 (C8H), 132.0 (Cipso,py), 127.1 (C1H), [C H(cym)], 88.4 [C H(cym)], 85.3 [C H(cym)], 31.2 [CH(CH ) ], 22.9
ar
ar
ar
ar
3 2
25.6 (CarHpara), 122.7 (C7H), 121.8 (C3H), 118.5 (C4H), 113.1 (C2H), [CH(CH ) ], 22.1 [CH(CH ) ], 19.2 [C CH (cym)] Anal. Calcd for
3 2
3 2
ar
3
12.7 (C6H), 105.4 [C CH (cym)], 104.4 (C5H), 99.3 [C iPr(cym)], 92.7
C H BrClN Ru (M = 541.97 g/mol): C: 50.89, H: 4.08, N: 5.16; found
23 22 2
ar
3
ar
[
C H(cym)], 89.5 [C H(cym)], 88.2 [C H(cym)], 84.8 [C H(cym)], 31.1
C: 51.20, H: 4.20, N: 5.25 %.
ar
ar
ar
ar
[
CH(CH ) ], 22.9 [CH(CH ) ], 22.0 [CH(CH ) ], 19.2 [C CH (cym)]. Anal.
3
2
3 2
3 2
ar
3
Calcd for C H ClN Ru (M = 464.06 g/mol): C: 59.54, H: 5.00, N:
23
23
2
2
Chloro[2-(4-nitrophenyl-κC )imidazolino[1,5-a]pyridin-3-ylidene-
6
.04; found C: 59.50, H: 5.13, N: 5.94 %.
3
6
κC ][η -1-methyl-4-(1-methylethyl)benzene]ruthenium(II) (4). 827 mg
3 mmol) of 2-(4-nitrophenyl)-2H-imidazo[1,5-a]pyridinium chloride
d, 919 mg (1.5 mmol) of [RuCl (η -p-cymene)] and 702 mg
3 mmol) of Ag O were placed in a Schlenk tube and 75 mL of
CH Cl were added. The resulting deep red suspension was stirred
at room temperature under exclusion of light for 4 d and the dark
solution was evaporated to ≈ 1/6 of its original volume. The result-
ing suspension was directly subjected to column chromatography
(
2
Chloro[2-(4-methoxyphenyl-κC )imidazolino[1,5-a]pyridin-3-ylidene-
6
3
6
2
2
κC ][η -1-methyl-4-(1-methylethyl)benzene]ruthenium(II) (2). 836 mg
3 mmol) of 2-(4-methoxyphenyl)-2H-imidazo[1,5-a]pyridinium
(
2
(
6
2
2
chloride b, 919 mg (1.5 mmol) of [RuCl (η -p-cymene)] and 702 mg
2
2
(
3 mmol) of Ag O were placed in a Schlenk tube and 75 mL of
2
CH Cl were added. The resulting deep red suspension was stirred
2
2
at room temperature under exclusion of light for 3 d and the dark
solution was evaporated to dryness. The dark solid is subjected to
column chromatography (SiO ; CH Cl /MeOH, 10:1; R = 0.9). The
(
SiO ; CH Cl /MeOH, 10:1; R = 0.9). The product fraction (broad
2 2 2 f
yellow band) was after evaporation dissolved in ≈ 250 mL of THF
and filtered through basic alumina. The yellow filtrate was reduced
until an orange to red solid started to precipitate. The product was
then slowly precipitated by addition of n-pentane (≈ 100 mL).
920 mg, 60 %; dec > 195 °C). H NMR (500 MHz, CDCl ) δ = 9.06
d, J = 2.4 Hz, 1H, C8H), 8.55 (dd, J = 7.3, 1.2 Hz, 1H, C1H), 7.90 (dd,
J = 8.5, 2.4 Hz, 1H, C7H), 7.70 (s, 1H, C5H), 7.33 (d, J = 8.6 Hz, 1H,
C6H), 7.27 ([partially obscured by solvent residual signal] d, J =
.3 Hz, 1H, C4H), 6.87–6.82 (m, 1H, C3H), 6.70–6.67 (m, 1H, C2H),
.76 [d, J = 5.9 Hz, 1H, C H(cym)], 5.72 [s, 2H, C H(cym)], 5.61 [d,
J = 5.9 Hz, 1H, C H(cym)], 2.14 [s, 3H, C CH (cym)], 2.13–2.07 [m,
2
2
2
f
product fraction (broad yellow band) is, after evaporation in vacuo,
dissolved in ≈ 25 mL of THF and filtered through basic alumina.
The yellow to orange product is slowly precipitated by addition of
1
(
pentane (≈ 25 mL). (430 mg, 29 %; m.p. 125–130 °C). 1H NMR
3
(
(
600 MHz, CDCl ) δ = 8.56 (dd, J = 7.3, 1.1 Hz, 1H, C1H), 7.81 (d, J =
3
2.6 Hz, 1H, C8H), 7.59 (d, J = 0.9 Hz, 1H, C5H), 7.24 (dt, J = 9.4,
1.3 Hz, 1H, C4H), 7.20 (d, J = 8.4 Hz, 1H, C6H), 6.76 (ddd, J = 9.3,
6.4, 1.0 Hz, 1H, C3H), 6.60 (ddd, J = 7.4, 6.4, 1.2 Hz, 1H, C2H), 6.55
1
5
ar
ar
(
dd, J = 8.4, 2.6 Hz, 1H, C7H), 5.64 [dd, J = 5.9, 1.3 Hz, 1H, C H(cym)],
ar
ar
ar
3
5
.62 [dd, J = 6.0, 1.2 Hz, 1H, C H(cym)], 5.57 [dd, J = 6.0, 1.3 Hz, 1H,
ar
1
3
H, CH(CH ) ], 0.81 [d, J = 6.9 Hz, 3H, CH(CH ) ], 0.68 [d, J = 6.9 Hz,
3 2 3 2
C H(cym)], 5.53 [dd, J = 5.9, 1.2 Hz, 1H, C H(cym)], 3.88 (s, 3H,
ar
ar
13
H, CH(CH ) ]. C NMR (126 MHz, CDCl ) δ = 181.2 (Ccarbene), 166.9
3
2
3
OCH ), 2.15–2.09 [m, 1H, CH(CH ) ], 2.09 [s, 3H, C CH (cym)], 0.81
3
3 2
ar
3
(
(
(
[
[
CRu), 150.6 (C N), 144.5 (C NO ), 136.0 (C8H) 132.6 (Cipso,py), 127.0
13
ar ar 2
[
d, J = 6.9 Hz, 3H, CH(CH ) ], 0.68 [d, J = 6.9 Hz, 3H, CH(CH ) ].
C
3
2
3 2
C1H), 122.7 (C3H), 119.5 (C7H), 118.7 (C4H), 113.9 (C2H), 112.3
C6H), 107.2 [C CH (cym)], 105.1 (C5H), 100.4 [C iPr(cym)], 93.2
C H(cym)], 90.1 [C H(cym)], 89.2 [C H(cym)], 85.7 [C H(cym)], 31.3
CH(CH ) ], 22.9 [CH(CH ) ], 22.1 [CH(CH ) ], 19.3 [C CH (cym)]. Anal.
Calcd for C H ClN O Ru (M = 509.04 g/mol): C: 54.28, H: 4.36, N:
NMR (151 MHz, CDCl ) δ = 177.4 (Ccarbene), 166.7 (CRu), 156.6
3
ar
3
ar
(
(
[
[
[
C OMe), 139.3 (C N), 131.9 (Cipso,py), 127.2 (C8H), 126.9 (C1H), 121.5
ar ar
ar
ar
ar
ar
C3H), 118.4 (C4H), 112.9 (C2H), 112.9 (C6H), 107.4 (C7H), 105.4
C CH (cym)], 104.3 (C5H), 99.1 [C iPr(cym)], 92.5 [C H(cym)], 89.2
3
2
3 2
3 2
ar
3
ar
3
ar
ar
23
22
3 2
C H(cym)], 88.2 [C H(cym)], 84.9 [C H(cym)], 55.6 (OCH ), 31.1
ar
ar
ar
3
8
.26; found C: 54.00, H: 4.35, N: 8.15 %.
CH(CH ) ], 22.9 [CH(CH ) ], 22.0 [CH(CH ) ], 19.2 [C CH (cym)]. Anal.
3
2
3 2
3 2
ar
3
Calcd for C H ClN ORu (M = 494.07 g/mol): C: 58.35, H: 5.10, N:
24
25
2
5
.67; found C: 58.48, H: 5.26, N: 5.77 %.
2
Chloro{2-[4-(ethoxycarbonyl)phenyl-κC ]imidazolino[1,5-a]pyridin-3-yl-
3
6
idene-κC }[η -1-methyl-4-(1-methylethyl)benzene]ruthenium(II) (5).
2
Chloro[2-(4-bromophenyl-κC )imidazolino[1,5-a]pyridin-3-ylidene- 908 mg (3 mmol) of 2-[4-(ethoxycarbonyl)phenyl]-2H-imidazo-
3
6
6
κC ][η -1-methyl-4-(1-methylethyl)benzene]ruthenium(II) (3). 929 mg
3 mmol) of 2-(4-bromophenyl)-2H-imidazo[1,5-a]pyridinium chlor-
[1,5-a]pyridinium chloride e, 919 mg (1.5 mmol) of [RuCl (η -p-cym-
ene)] and 702 mg (3 mmol) of Ag O were placed in a Schlenk tube
and 50 mL of CH Cl were added. The resulting deep red suspen-
2
(
2
2
6
ide c, 919 mg (1.5 mmol) of [RuCl (η -p-cymene)] and 702 mg
2
2
2 2
(
3 mmol) of Ag O were placed in a Schlenk tube and 70 mL of
sion was stirred at room temperature under exclusion of light for
6 © 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2
Eur. J. Inorg. Chem. 0000, 0–0
www.eurjic.org

Full Paper
2
d and the dark solution was evaporated to dryness. The dark solid
General Synthetic Procedure to the Bisheteroleptic Bipyridyl Com-
plexes
was subjected to column chromatography (SiO ; CH Cl /MeOH,
2
2
2
1
0:1; R = 0.85–0.95). The product fraction (broad yellow band) was,
f
NMR numbering scheme
after evaporation in vacuo, dissolved in ≈ 100 mL of THF/Et O, 1:1
2
and filtered through basic alumina. The yellow filtrate was reduced
until a yellow to orange solid started to precipitate. The product
was then slowly precipitated by addition of n-pentane (≈ 100 mL)
and storing the suspension in a refrigerator (3 °C) overnight.
1
(
(
860 mg, 54 %; dec > 210 °C). H NMR (600 MHz, CDCl ) δ = 8.91
3
d, J = 1.8 Hz, 1H, C8H), 8.57 (dt, J = 7.3, 1.1 Hz, 1H, C1H), 7.75 (dd,
J = 8.1, 1.8 Hz, 1H, C7H), 7.69 (d, J = 0.9 Hz, 1H, C5H), 7.30 (d, J =
.1 Hz, 1H, C6H), 7.27 (dd [partially obscured by solvent residual
signal], J = 1.2 Hz, 1H, C4H), 6.81 (ddd, J = 9.3, 6.4, 0.9 Hz, 1H, C2H),
.64 (ddd, J = 7.4, 6.3, 1.1 Hz, 1H, C3H), 5.71 [td, J = 5.9, 1.2 Hz, 2H,
C (cym)H], 5.67 [dd, J = 6.1, 1.2 Hz, 1H, C (cym)H], 5.56 [dd, J =
8
6
ar
ar
5
.9, 1.2 Hz, 1H, C (cym)H], 4.47–4.34 (m, 2H, CH CH ), 2.12 [s, 3H,
In a Schlenk-tube 1 eq of the corresponding p-cymene complex
and 2.1–2.2 eq of bipyridine were dissolved in small amounts of
DMSO (degassed, dried with molecular sieves 4 Å) and heated to
140 °C for 20 h under the exclusion of light. The resulting deep
purple solution was slowly cooled to room temperature and diluted
ar
2
3
C (cym)CH ], 2.10–2.06 [m, 1H, CH(CH ) ], 1.44 (t, J = 7.1 Hz, 3H,
CH CH ), 0.80 [d, J = 6.9 Hz, 3H, CH(CH ) ], 0.67 [d, J = 6.9 Hz, 3H,
CH(CH ) ]. C NMR (151 MHz, CDCl ) δ = 180.8 (Ccarbene), 167.5
ar
3
3 2
2
3
3 2
13
3
2
3
(COOEt), 164.6 (CRu), 149.1 (C N), 142.8 (C8H), 132.3 (Cipso,py), 127.1
ar
(
C1H), 126.9 (C COOEt), 125.2 (C7H), 122.3 (C2H), 118.6 (C4H), 113.4 with water to an approx. five- to sevenfold volume. The deep purple
ar
(
[
8
2
C3H), 112.2 (C6H), 106.4 [CarCH (cym)], 104.8 (C5H), 99.6
aqueous solution containing the corresponding chloride complex
was left to stand in the refrigerator overnight and subsequently
filtered through a pad of diatomaceous earth to remove residual
bipyridine. A solution of 1.25 eq of ammonium hexafluorophos-
phate was then slowly added to the filtrate and the resulting dark
violet precipitate was filtered via cannula or a sintered glass frit.
The solid was dried in vacuo, dissolved in small amounts of di-
chloromethane, and the solution was slowly filtered through a pad
3
C iPr(cym)], 93.2 [C H(cym)], 89.7 [C H(cym)], 88.5 [C H(cym)],
ar
ar
ar
ar
5.1 [C H(cym)], 60.8 (CH CH ), 31.2 [CH(CH ) ], 23.0 [CH(CH ) ],
ar 2 3 3 2 3 2
2.0 [CH(CH ) ], 19.2 [C CH (cym)], 14.7 (CH CH ). Anal. Calcd for
3
2
ar
3
2
3
C H ClN O Ru (M = 536.08 g/mol): C: 58.26, H: 5.08, N: 5.23; found
C: 58.42, H: 4.96, N: 5.00 %.
26
27
2 2
2
Chloro{2-[3,5-bis(trifluoromethyl)phenyl-κC ]imidazolino[1,5-a]pyri- of basic aluminum oxide. Addition of diethyl ether to the deep
3
6
din-3-ylidene-κC }[η -1-methyl-4-(1-methylethyl)benzene]ruthe-
nium(II) (6): 1254 mg (3 mmol) of 2-[3,5-bis(trifluoromethyl)phenyl]- complexes as analytically pure hexafluorophosphate salts.
H-imidazo[1,5-a]pyridinium tetrafluoroborate f, 919 mg (1.5 mmol)
violet filtrate and subsequent filtration gave the bisheteroleptic
2
2
3
[
2-(Phenyl-κC )imidazolino[1,5-a]pyridin-3-ylidene-κC ]-bis(2,2′-bipyr-
6
of [RuCl (η -p-cymene)] and 702 mg (3 mmol) of Ag O were placed
in a Schlenk tube and 75 mL of CH Cl were added. The resulting
deep red suspension was stirred at room temperature under exclu-
sion of light for 3 d and the dark solution was evaporated to ≈ 1/6
of its original volume. The resulting suspension was directly sub-
2
2
2
idine-κN,κN′)ruthenium(II) (1+) Hexafluorophosphate (7): The synthe-
sis followed the general procedure using 186 mg (0.4 mmol) of
complex 1 and 137 mg (0.88 mmol) of bpy in 5 mL of DMSO. The
precipitation was carried out using 82 mg (0.5 mmol) of NH PF .
2
2
4
6
The analytically pure complex was obtained after filtering over basic
jected to column chromatography (SiO ; CH Cl /MeOH, 10:1; R =
0
2
2
2
f
alumina twice and adding a mixture of diethyl ether/n-pentane to
.5–0.8). The product fraction (broad yellow band) was, after evapo-
1
the filtrate. (65 mg, 21 %; m.p. 205 °C). H NMR (600 MHz, CD CN)
3
ration in vacuo, dissolved in ≈ 250 mL of THF and filtered through
basic alumina. The yellow filtrate was reduced until an orange solid
started to precipitate. A first fraction of the product was then slowly
precipitated by addition of n-pentane (≈ 100 mL). The filtrate was
δ = 8.41 (dt, J = 8.3, 1.1 Hz, 1H, CbpyH), 8.36 (dt, J = 8.2, 1.1 Hz, 1H,
CbpyH), 8.31 (ddd, J = 8.3, 1.4, 0.8 Hz, 1H, CbpyH), 8.26 (ddd, J = 8.2,
1
5
.4, 0.8 Hz, 1H, CbpyH), 8.11 (d, J = 1.0 Hz, 1H, C5H), 8.02 (ddd, J =
.4, 1.5, 0.8 Hz, 1H, CbpyH), 7.99–7.94 (m, 2H, CbpyH), 7.93 (ddd, J =
evaporated, subjected to column chromatography (SiO ; CH Cl /
2
2
2
8.2, 7.6, 1.6 Hz, 1H, CbpyH), 7.83 (ddd, J = 5.7, 1.5, 0.8 Hz, 1H, CbpyH),
7.77 (ddd, J = 8.2, 7.5, 1.6 Hz, 1H, CbpyH), 7.72 (ddd, J = 8.2, 7.5,
MeOH, 15:1; R = 0.8–0.9) and again purified over basic alumina and
f
precipitated as described above. (71 mg, 4 %; dec > 205 °C). 1
NMR (500 MHz, CDCl ) δ (ppm) = 8.43 (dd, J = 7.3, 1.1 Hz, 1H, C H),
H
1.5 Hz, 1H, CbpyH), 7.56 (ddd, J = 5.5, 1.6, 0.8 Hz, 1H, CbpyH), 7.52
3
ar
(dd, J = 7.5, 1.1 Hz, 1H, C6H), 7.39 (ddd, J = 7.5, 5.4, 1.2 Hz, 1H,
CbpyH), 7.34 (ddd, J = 7.5, 5.5, 1.3 Hz, 1H, CbpyH), 7.31 (dt, J = 9.4,
1.2 Hz, 1H, C4H), 7.14 (ddd, J = 7.5, 5.7, 1.4 Hz, 1H, CbpyH), 7.06
(ddd, J = 7.4, 5.7, 1.4 Hz, 1H, CbpyH), 6.93 (ddd, J = 7.8, 7.3, 1.4 Hz,
7
7
6
.75 (d, J = 0.9 Hz, 1H, C5H), 7.74 (s, 1H, CarHpara), 7.57 (s, 1H, C6H),
.32 (d, J = 9.3 Hz, 1H, C H), 6.87 (ddd, J = 9.4, 6.4, 0.9 Hz, 1H, C H),
ar
ar
.67 (ddd, J = 7.4, 6.3, 1.1 Hz, 1H, C H), 5.89 [d, J = 5.9 Hz, 1H,
ar
C H(cym)], 5.75 [dd, J = 6.2, 1.3 Hz, 1H, C H(cym)], 5.70 [dd, J = 1H, C7H), 6.74–6.70 (m, 2H, C1H + CarHpara), 6.64 (ddd, J = 9.2, 6.4,
ar
ar
5
1
3
.9, 1.3 Hz, 2H, C H(cym)], 2.18 [s, 3H, C CH (cym)], 1.85–1.77 [m,
0.9 Hz, 1H, C3H), 6.38 (ddd, J = 7.2, 1.4, 0.5 Hz, 1H, C8H), 6.11 (ddd,
ar
ar
3
J = 7.5, 6.4, 1.2 Hz, 1H, C2H). 13C NMR (151 MHz, CD CN) δ = 187.6
H, CH(CH ) ], 0.65 [d, J = 6.9 Hz, 3H, CH(CH ) ], 0.62 [d, J = 6.9 Hz,
3
2
3 2
3
13
H, CH(CH ) ]. C NMR (126 MHz, CDCl ) δ = 179.8 (Ccarbene), 170.6 (Ccarbene), 176.6 (CRu), 158.3 (Cipso,bpy), 157.4 (Cipso,bpy), 156.5
3
2
3
(
CRu), 147.6 (C N), 141.7–140.2 (m, 2 × C CF ), 132.7 (Cipso,py), (Cipso,bpy), 156.4 (Cipso,bpy), 155.4 (CbpyH), 155.2 (CbpyH), 150.0 (CbpyH),
ar ar 3
1
29.5–122.3 (weak, m, 2C, C CF ), 126.7 (C H), 122.8 (C H), 120.2 149.2 (CbpyH), 149.0 (C N), 137.5 (C8H), 136.8 (CbpyH), 136.5 (CbpyH),
ar 3 ar ar
ar
(
C H ), 118.5 (C H), 113.8 (C H), 110.7 (C6H), 104.7 (C5H), 91.6 135.2 (CbpyH), 134.5 (CbpyH), 132.6 (Cipso,py), 127.7 (CbpyH), 127.6
ar para ar ar
[
3
C H(cym)], 89.8 [weak, C H(cym)], 88.8, 87.9 [weak, C H(cym)],
(CbpyH), 127.1 (CbpyH), 126.9 (CbpyH), 126.1 (C1H), 125.8 (CarHpara),
124.2 (CbpyH), 124.2 (CbpyH), 124.1 (CbpyH), 123.6 (CbpyH), 122.3 (C3H),
122.2 (C7H), 119.5 (C4H), 113.5 (C2H), 113.3 (C6H), 106.7 (C5H). Anal.
Calcd for C H F N PRu·0.25CH Cl (M = 773.07 g/mol): C: 51.67,
ar
ar
ar
1.0 [CH(CH ) ], 22.3 [CH(CH ) ], 22.2 [CH(CH ) ], 19.0 [C CH (cym)]
3 2 3 2 3 2 ar 3
[Car,ipso(cym) signals not detectable]. Anal. Calc. for C H ClF N Ru
25 21 6 2
(
3
M = 600.03 g/mol): C: 50.05, H: 3.53, N: 4.67; found C: 50.25, H:
.42, N: 4.65 %.
33
25
6
6
2
2
H: 3.33, N: 10.87; found C: 51.76 H: 3.16 N: 10.83 %.
Eur. J. Inorg. Chem. 0000, 0–0
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7
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
2
3
[
2-(4-Methoxyphenyl-κC )imidazolino[1,5-a]pyridin-3-ylidene-κC ]- 107.0 (C5H). Anal. Calcd for C33H24BrF N PRu·0.25CH Cl (M =
6 6 2 2
bis(2,2′-bipyridine-κN,κN′)ruthenium(II) (1+) Hexafluorophosphate (8):
850.98 g/mol): C: 46.89, H: 2.90, N: 9.87; found C: 46.84, H: 2.96,
N: 9.67 %.
1
48 mg (0.3 mmol) of complex 2 and 98 mg (0.63 mmol) of bpy
were dissolved in 15 mL of MeCN and the resulting mixture was
refluxed for 18 h under the exclusion of light. The solution was
evaporated to ≈ 1/2 its original volume and 25 mL of diethyl ether
were added. The solvent was filtered off via cannula and the re-
maining red solid was dissolved in small amounts of dichloro-
methane and filtered through diatomaceous earth. The filtrate was
concentrated and the resulting crude chloride complex was dried
in vacuo (120 mg). The chloride complex was then dissolved in
2
3
[
2-(4-Nitrophenyl-κC )imidazolino[1,5-a]pyridin-3-ylidene-κC ]-
bis(2,2′-bipyridine-κN,κN′)ruthenium(II) (1+) hexafluorophosphate
10). 153 mg (0.3 mmol) of complex 4 and 98 mg (0.63 mmol) of
(
bpy were dissolved in 15 mL of MeCN and the resulting mixture
was refluxed for 70 h under the exclusion of light. The solution was
evaporated to ≈ 1/3 its original volume and 15 mL of diethyl ether
were added. The mixture was stored in a refrigerator overnight, the
solvent was filtered off via cannula and the remaining red solid was
dried in vacuo (120 mg). The chloride complex was then dissolved
in 10 mL of water, the deep red-violet solution was filtered through
diatomaceous earth and a solution of 42 mg (0.26 mmol) of NH PF
in 2 mL of water was slowly added. The crude product precipitated
as a dark red-violet solid. After filtration of a DCM solution over
basic alumina and precipitating by addition of a mixture of diethyl
ether/n-pentane the analytically pure complex was obtained as a
dark violet crystalline solid. (86 mg, 36 %; m.p. 325 °C). H NMR
600 MHz, CD CN) δ = 8.43 (dt, J = 8.3, 1.1 Hz, 1H, CbpyH), 8.41 (dt,
J = 8.3, 1.1 Hz, 1H, CbpyH), 8.33 (dt, J = 8.3, 1.0 Hz, 1H, CbpyH), 8.29
dt, J = 8.3, 1.0 Hz, 1H, CbpyH), 8.18 (d, J = 0.9 Hz, 1H, C5H), 8.03–
.96 (m, 3H, CbpyH), 7.86 (ddd, J = 5.7, 1.4, 0.6 Hz, 1H, CbpyH), 7.84–
.77 (m, 3H, C7H + 2 × CbpyH), 7.76 (td, J = 7.9, 1.5 Hz, 1H, CbpyH),
.65 (d, J = 8.6 Hz, 1H, C6H), 7.58 (dd, J = 5.5, 1.4 Hz, 1H, CbpyH),
.42 (ddd, J = 7.1, 5.4, 1.3 Hz, 2H, CbpyH), 7.32 (dt, J = 9.5, 1.3 Hz,
H, C4H), 7.21 (d, J = 2.5 Hz, 1H, C8H), 7.14 (ddd, J = 7.4, 5.7, 1.4 Hz,
H, CbpyH), 7.10 (ddd, J = 7.4, 5.8, 1.3 Hz, 1H, CbpyH), 6.71 (dd, J =
.5, 1.2 Hz, 1H, C1H), 6.68 (ddd, J = 9.4, 6.4, 0.9 Hz, 1H, C3H), 6.14
ddd, J = 7.6, 6.4, 1.2 Hz, 1H, C2H). C NMR (151 MHz, CD CN) δ =
90.3 (Ccarbene), 180.3 (CRu), 158.2 (Cipso,bpy), 157.3 (Cipso,bpy), 156.4
Cipso,bpy), 156.3 (Cipso,bpy), 155.7 (CbpyH), 155.6 (CbpyH), 155.3 (C N),
50.2 (CbpyH), 149.3 (CbpyH), 145.8(C NO ), 137.4 (CbpyH), 137.2
ar 2
CbpyH), 135.9 (CbpyH), 135.5 (CbpyH), 133.4 (Cipso,py), 131.5 (C8H),
28.0 (CbpyH), 127.9 (CbpyH), 127.5 (CbpyH), 127.3 (CbpyH), 126.3 (C1H),
24.5 (CbpyH), 124.4 (CbpyH), 124.4 (CbpyH), 124.1 (CbpyH), 123.2 (C3H),
19.7 (C4H), 118.9 (C7H), 114.1 (C2H), 113.0 (C6H), 107.6 (C5H). Anal.
10 mL of water, the deep red-violet solution was filtered through
diatomaceous earth and a solution of 42 mg (0.26 mmol) of NH PF6
4
in 2 mL of water was slowly added. The crude product precipitated
as a dark red-violet solid. After filtration of a DCM solution over
basic alumina and subsequent evaporation the analytically pure
complex was obtained. (71 mg, 30 %; m.p. 325 °C). 1H NMR
4
6
(
600 MHz, CD CN) δ = 8.41 (dt, J = 8.4, 1.1 Hz, 1H, CbpyH), 8.36 (dt,
3
J = 8.3, 1.1 Hz, 1H, CbpyH), 8.31 (dt, J = 8.3, 1.0 Hz, 1H, CbpyH), 8.26
1
(
(
dt, J = 8.3, 1.0 Hz, 1H, CbpyH), 8.04–8.02 (m, 2H, C5H + CbpyH), 8.00
dd, J = 5.9, 1.9 Hz, 1H, CbpyH), 7.97 (td, J = 7.9, 1.5 Hz, 1H, CbpyH),
(
3
7
.92 (td, J = 7.8, 1.6 Hz, 1H, CbpyH), 7.83 (dt, J = 5.8, 1.1 Hz, 1H,
(
CbpyH), 7.77 (td, J = 7.8, 1.6 Hz, 1H, CbpyH), 7.72 (td, J = 7.9, 1.5 Hz,
7
7
7
7
1
1
7
(
1
(
1
1H, CbpyH), 7.56 (dt, J = 5.6, 1.1 Hz, 1H, CbpyH), 7.45 (d, J = 8.4 Hz,
1H, C6H), 7.39 (ddd, J = 7.3, 5.5, 1.2 Hz, 1H, CbpyH), 7.34 (ddd, J =
7.3, 5.5, 1.3 Hz, 1H, CbpyH), 7.29 (dt, J = 9.4, 1.3 Hz, 1H, C1H), 7.15
(ddd, J = 7.3, 5.8, 1.4 Hz, 1H, CbpyH), 7.07 (ddd, J = 7.4, 5.9, 1.4 Hz,
1
0
7
H, CbpyH), 6.68 (dt, J = 7.5, 1.1 Hz, 1H, C4H), 6.62 (ddd, J = 9.3, 6.4,
.9 Hz, 1H, C2H), 6.46 (dd, J = 8.4, 2.7 Hz, 1H, C7H), 6.10 (ddd, J =
.5, 6.4, 1.2 Hz, 1H, C3H), 5.82 (d, J = 2.7 Hz, 1H, C8H), 3.52 (s, 3H,
13
3
13
OCH3). C NMR (151 MHz, CD CN) δ = 185.8 (Ccarbene), 179.2 (CRu),
3
1
58.3 (Cipso,bpy), 158.0 (C O), 157.4 (Cipso,bpy), 156.6 (Cipso,bpy), 156.5
ar
ar
(Cipso,bpy), 155.4 (CbpyH), 155.1 (CbpyH), 150.1 (CbpyH), 149.3 (CbpyH),
1
42.8 (C N), 136.8 (CbpyH), 136.5 (CbpyH), 135.2 (CbpyH), 134.5
ar
(
(CbpyH), 132.6 (Cipso,py), 127.7 (CbpyH), 127.6 (CbpyH), 127.1 (CbpyH),
1
1
1
1
27.0 (CbpyH), 126.0 (C4H), 124.3 (CbpyH), 124.2 (CbpyH), 124.2
(CbpyH), 123.7 (CbpyH), 123.1 (C8H), 122.1 (C2H), 119.4 (C1H), 113.7
(
C6H), 113.5 (C3H), 106.6 (C5H), 106.2 (C7H), 55.2 (OCH ). Anal. Calcd
3
Calcd for C H F N O PRu (M = 797.07 g/mol): C: 49.75, H: 3.04, N:
3
3 24 6 7 2
for C H F N OPRu (M = 782.09 g/mol): C: 52.24, H: 3.48, N: 10.75;
34 27 6 6
1
2.31; found C: 49.42, H: 3.17, N: 12.10 %.
found C: 52.11, H: 3.58, N: 10.57 %.
2
{
2-[4-(Ethoxycarbonyl)phenyl-κC ]imidazolino[1,5-a]pyridin-3-ylidene-
κC }-bis(2,2′-bipyridine-κN,κN′)ruthenium(II) (1+) Hexafluorophos-
2
3
3
[
2-(4-Bromophenyl-κC )imidazolino[1,5-a]pyridin-3-ylidene-κC ]-
bis(2,2′-bipyridine-κN,κN′)ruthenium(II) (1+) Hexafluorophosphate (9).
phate (11). The synthesis followed the general procedure using
The synthesis followed the general procedure using 163 mg 268 mg (0.5 mmol) of complex 5 and 172 mg (1.1 mmol) of bpy in
(
0.3 mmol) of complex 3 and 103 mg (0.66 mmol) of bpy in 4 mL
5 mL of DMSO. The precipitation was carried out using 103 mg
1
of DMSO. The precipitation was carried out using 61 mg
(0.625 mmol) of NH PF . (180 mg, 44 %; m.p. 215 °C). H NMR
4
6
1
(0.375 mmol) of NH PF . (105 mg, 41 %; m.p. 325–330 °C). H NMR
(600 MHz, CD CN) δ = 8.42 (dt, J = 8.2, 1.1 Hz, 1H, CbpyH), 8.38 (dt,
4
6
3
(
600 MHz, CD CN) δ = 8.43–8.36 (m, 2H, CbpyH), 8.33–8.28 (m, 2H,
J = 8.2, 1.1 Hz, 1H, CbpyH), 8.32 (dt, J = 8.2, 1.2 Hz, 1H, CbpyH), 8.26
3
CbpyH), 8.09 (d, J = 0.9 Hz, 1H, C5H), 8.00–7.97 (m, 1H, CbpyH), 7.97– (dt, J = 8.3, 0.8 Hz, 1H, CbpyH), 8.14 (d, J = 1.0 Hz, 1H, C5H), 8.03
.96 (m, 1H, CbpyH), 7.96–7.94 (m, 1H, CbpyH), 7.80–7.78 (m, 2H, (ddd, J = 5.4, 1.6, 0.8 Hz, 1H, CbpyH), 8.01–7.95 (m, 2H, CbpyH), 7.88
7
CbpyH), 7.76 (ddd, J = 8.2, 7.6, 1.5 Hz, 1H, CbpyH), 7.54 (ddd, J = 5.5,
(ddd, J = 5.7, 1.6, 0.8 Hz, 1H, CbpyH), 7.83 (ddd, J = 5.8, 1.5, 0.8 Hz,
1H, CbpyH), 7.79 (ddd, J = 8.3, 7.6, 1.6 Hz, 1H, CbpyH), 7.75–7.71 (m,
1H, CbpyH), 7.59–7.56 (m, 3H, C6H + C7H + CbpyH), 7.42–7.37 (m,
1.6, 0.8 Hz, 1H, CbpyH), 7.44 (d, J = 8.2 Hz, 1H, C6H), 7.40–7.38 (m,
H, CbpyH), 7.37–7.33 (m, 2H, CbpyH), 7.30 (dt, J = 9.4, 1.2 Hz, 1H,
1
C4H), 7.17 (ddd, J = 7.5, 5.7, 1.4 Hz, 1H, CbpyH), 7.10–7.08 (m, 1H, 2H, CbpyH), 7.31 (dt, J = 9.4, 1.3 Hz, 1H, C4H), 7.13 (ddd, J = 7.2, 5.7,
CbpyH), 7.07 (dd, J = 8.2, 2.2 Hz, 1H, C7H), 6.67 (dd, J = 7.4, 1.1 Hz,
1.3 Hz, 1H, CbpyH), 7.07 (ddd, J = 7.2, 5.7, 1.4 Hz, 1H, CbpyH), 7.02 (t,
J = 1.2 Hz, 1H, C8H), 6.73 (dq, J = 7.4, 1.1 Hz, 1H, C1H), 6.66 (ddd,
J = 9.4, 6.4, 1.0 Hz, 1H, C3H), 6.13 (ddd, J = 7.5, 6.4, 1.2 Hz, 1H, C2H),
1
H, C1H), 6.64 (ddd, J = 9.3, 6.4, 0.9 Hz, 1H, C3H), 6.41 (d, J = 2.2 Hz,
1
3
1H, C8H), 6.11 (ddd, J = 7.4, 6.4, 1.2 Hz, 1H, C2H). C NMR (151 MHz,
CD CN) δ = 187.5 (Ccarbene), 181.9 (CRu), 158.1 (Cipso,bpy), 157.3 4.13 (2 × d, J = 7.1 Hz, 2H, CH CH ), 1.20 (t, J = 7.1 Hz, 3H, CH CH ).
3
2
3
2
3
13
(
(
(
Cipso,bpy), 156.4 (Cipso,bpy), 156.3 (Cipso,bpy), 155.5 (CbpyH), 155.3
C NMR (151 MHz, CD CN) δ = 189.4 (Ccarbene), 177.1 (CRu), 167.9
3
CbpyH), 150.1 (CbpyH), 149.2 (CbpyH), 148.4 (C N), 139.2 (C8H), 137.1
CbpyH), 136.8 (CbpyH), 135.6 (CbpyH), 135.0 (CbpyH), 132.8 (Cipso,py),
(COO), 158.3 (Cipso,bpy), 157.4 (Cipso,bpy), 156.5 (Cipso,bpy), 156.4
ar
(Cipso,bpy), 155.6 (CbpyH), 155.4 (CbpyH), 153.4 (C N), 150.2 (CbpyH),
ar
1
1
1
29.3 (CbpyH), 127.8 (CbpyH), 127.3 (CbpyH), 127.1 (CbpyH), 126.1 (C1H),
24.6 (C7H), 124.3 (CbpyH), 124.3 (CbpyH), 124.3 (CbpyH), 123.9 (CbpyH),
149.3 (CbpyH), 138.2 (C8H), 137.1 (CbpyH), 136.9 (CbpyH), 135.6
(CbpyH), 135.0 (CbpyH), 133.1 (Cipso,py), 127.8 (CbpyH), 127.8 (CbpyH),
22.6 (C3H), 119.7 (C Br), 119.5 (C4H), 115.0 (C6H), 113.7 (C2H),
127.3 (CbpyH), 127.2 (C COO), 127.1 (CbpyH), 126.3 (C1H), 124.4
ar
ar
Eur. J. Inorg. Chem. 0000, 0–0
www.eurjic.org
8
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
(
(
(
8
1
CbpyH), 124.3 (CbpyH), 124.3 (C7H + CbpyH), 123.8 (CbpyH), 122.8
C3H), 119.6 (C4H), 113.9 (C2H), 112.9 (C6H), 107.2 (C5H), 61.1
CH CH ), 14.5 (CH CH ). Anal. Calcd for C36H29F N O PRu (M =
24.10 g/mol): C: 52.49, H: 3.55, N: 10.20; found C: 52.27, H: 3.42, N:
0.28 %.
[12] L. Mercs, A. Neels, H. Stoeckli-Evans, M. Albrecht, Inorg. Chem. 2011, 50,
8
188–8196.
[
13] S. Aghazada, I. Zimmermann, V. Scutelnic, M. K. Nazeeruddin, Organome-
tallics 2017, 36, 2397–2403.
2
3
2
3
6
6
2
[
14] C. H. Leung, C. D. Incarvito, R. H. Crabtree, Organometallics 2006, 25,
6
099–6107.
Supporting Information (see footnote on the first page of this
article): Crystallographic data for structures 1–7, 10, 11; CV spectra
of compounds 7–11, H and C NMR spectra of compounds a, d,
e, 1–11 can be found in the supporting information of this paper.
[15] a) S. Sinn, B. Schulze, C. Friebe, D. G. Brown, M. Jäger, E. Altuntas, J.
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1
13
CCDC 1859023 (for 11), 1859024 (for 4), 1859025 (for 6), 1859026
5
2, 7448–7459.
(
(
for 2), 1859027 (for 5), 1859028 (for 1), 1859029 (for 3), 1859030
for 7), and 1859031 (for 10) contain the supplementary crystallo-
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graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre.
1
557–1570; c) B. Schulze, D. Escudero, C. Friebe, R. Siebert, H. Görls, U.
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18] V. W.-W. Yam, B. W.-K. Chu, C.-C. Ko, K.-K. Cheung, J. Chem. Soc., Dalton
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Conflict of Interest
[
[
The authors declare no conflict of interest.
Acknowledgments
The authors would like to thank Susanne Nowotni for assistance
in the synthesis of complexes 5 and 11 as well as Hendrik Leo-
pold for data collection and refinement of structure 11. We are
grateful to the Center for Information Services and High Per-
formance Computing (ZIH) of Technical University Dresden for
computation time and technical support.
[
3
1
868; b) J. P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett. 1997, 78,
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[
22] Gaussian 16, Revision A.03, M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, G. A.
Petersson, H. Nakatsuji, X. Li, M. Caricato, A. V. Marenich, J. Bloino, B. G.
Janesko, R. Gomperts, B. Mennucci, H. P. Hratchian, J. V. Ortiz, A. F. Izmay-
lov, J. L. Sonnenberg, D. Williams-Young, F. Ding, F. Lipparini, F. Egidi,
J. Goings, B. Peng, A. Petrone, T. Henderson, D. Ranasinghe, V. G.
Zakrzewski, J. Gao, N. Rega, G. Zheng, W. Liang, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, T. Vreven, K. Throssell, J. A. Montgomery, Jr., J. E. Peralta, F.
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Keywords: Ruthenium · N-heterocyclic carbenes ·
Imidazopyridine · Bisheteroleptic · Cyclic voltammetry
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Bridging Ligands
D. Schleicher, A. Tronnier, J. Soellner,
T. Strassner* ...................................... 1–11
Cyclometalated Ruthenium(II) NHC
Complexes with Imidazo[1,5-a]pyr-
^
idine-Based (C C*) Ligands – Syn-
thesis and Characterization
Ruthenium complexes bearing cyclo- motif are synthesized and fully charac-
metalated N-heterocyclic carbene terized via NMR, UV/Vis, CV, and X-ray
based on an imidazo[1,5-a]pyridine techniques.
DOI: 10.1002/ejic.201900108
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim