Synthesis, structures and comparison of neutral complexes formed by 2-(2′-pyridyl)indole and d6 transition metals

Article abstract of DOI:10.1002/ejic.200600730

2-(2′-Pyridyl)indole acts as an N,N-bidentate ligand when deprotonated and forms (1-amido-4-imine)metanacycles with Re^I, Ru^II, Rh^III and Ir^III. The crystal structures of 2-(2′-pyridyl)indole and the complexes [Re(C₁₃H ₉N₂)(CO)₂-(PPh₃)₂], [Ru(C₁₃H₉N₂)(η⁶-C ₆Me₆)Cl], [Rh(C₁₃H₉N ₂)(η⁵-C₅Me₅)Cl] and [Ir(C ₁₃H₉N₂)(η⁵-C₅Me ₅)Cl] are presented and their spectra discussed. This provides a foundation for the increased use of this ligand, which is a prototype of a monoanionic, bidentate N,N-chelating ligand. The introduction of negatively charged N,N-bidentate ligands can increase the possibility of synthesising complexes tailored to catalysis and other applications. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200600730

FULL PAPER
DOI: 10.1002/ejic.200600730
Synthesis, Structures and Comparison of Neutral Complexes Formed by
2-(2Ј-Pyridyl)indole and d6 Transition Metals
Bernd Neumann,[a] Christoph Krinninger,[a] and Ingo-Peter Lorenz*[a]
Keywords: Metallacycles / N ligands / Rhenium / Ruthenium / Rhodium / Iridium
2-(2Ј-Pyridyl)indole acts as an N,N-bidentate ligand when
increased use of this ligand, which is a prototype of a
monoanionic, bidentate N,N-chelating ligand. The introduc-
tion of negatively charged N,N-bidentate ligands can in-
crease the possibility of synthesising complexes tailored to
catalysis and other applications.
deprotonated and forms (1-amido-4-imine)metallacycles
with ReI RuII, RhIII and IrIII. The crystal structures of 2-(2Ј-
,
pyridyl)indole and the complexes [Re(C13H9N2)(CO)2-
(PPh3)2],
[Ru(C13H9N2)(η6-C6Me6)Cl],
[Rh(C13H9N2)(η5-
C5Me5)Cl] and [Ir(C13H9N2)(η5-C5Me5)Cl] are presented and
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
their spectra discussed. This provides a foundation for the
such complexes. Secondly, they may facilitate proton chan-
nelling in or out of the complex centre, with the overall
complex remaining mostly intact. Most catalytic cycles
known in homogeneous catalysis involve the formation and
modification of metal hydrides and protons. Both substrate
movement towards and away from the complex as isomeris-
ation occurs within a catalytic cycle will be affected by a
proton acceptor. Thirdly, a bidentate ligand allows the for-
mer process to take place without cleavage of the ligand
from the complex as an anionic ligand is more likely to
tolerate an intermediate protonated stage than a neutral li-
gand. We selected 2-(2Ј-pyridyl)indole (Hpyind) as the first
ligand to be examined within a series of noble metal com-
plexes. After deprotonation, Hpyind is capable of acting as
a 1,4-chelate, with one of the nitrogen donor atoms being
an imine and the other being an amido function
(Scheme 1). Further N,N- and N,P-chelating ligands will be
presented and discussed in future publications.
Introduction
Chelating ligands play an important role both in classical
coordination chemistry and in modern organometallic
chemistry. Both symmetrical and asymmetrical chelates
with the same type of donor atoms or asymmetrical ones
with different donor atoms have been reported, and the for-
mation of five-membered metallacycles has been found to
be preferred due to the increased stability of the resulting
complexes. A 1,4-relationship of the donor atoms allows
complexation of a broad range of metal ions in tetrahedral,
octahedral and square-planar geometries. This can be
achieved by minor changes in the ligand’s geometry. Asym-
metric chelation with two identical donor atoms occurs in
two different types. First, the backbone bridge of the chelat-
ing ligand can induce asymmetry, as is observed with the
axially chiral BINAP and related ligands.[1] Second, the two
donor atoms can be electronically different, with one being
assigned a negative charge or coordinating with sp2 or sp3
free electron pairs. Among the N,N-bidentate ligands, two
types of symmetrical ligands have found widespread use,
namely neutral diamine ligands such as ethylenediamine
(en) and neutral diimine ligands like bipyridine (bpy) or
1,10-phenanthroline (phen). However, nonsymmetric an-
ionic bidentate ligands have so far been much less investi-
gated even though ligands of this type should be useful for
several reasons. Firstly, they can be used to adjust the over-
all charge of the complex, which allows high formal oxi-
dation states of the central atom to remain stable within
Scheme 1. General numbering (except crystal structures) and reac-
tion scheme.
[a] Ludwig Maximilian University Munich, Department of Chem-
istry and Biochemistry,
Hpyind is a well-known molecule that has been investi-
gated in several recent publications. Indeed, complexes with
pyind-like structures included in a larger molecule were de-
scribed[2,3] even before the first detailed study on the behav-
Butenandtstr. 5–13, 81377 Munich, Germany
Fax: +49-89-2180-77867
E-mail: ipl@cup.uni-muenchen.de
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
472
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Neutral Complexes of 2-(2Ј-Pyridyl)indole and d6 Transition Metals
FULL PAPER
iour of Hpyind itself as a ligand was presented by Thummel
et al.[4] Since the first isolated and structurally characterised
pyind complex[5] with RhI was described, some other re-
lated complexes have been reported.[6–9] Recent work has
concerned not only pyind complexes as catalysts in hydro-
arylation[10] and the Heck reaction,[11] but also its use in
optical devices.[12–16] It has also been used in an organome-
tallic mimic for the protein kinase staurosporin.[17–21] The
authors of the latter complex pointed out the “solely struc-
tural role” of an inert ruthenium complex in the biological
activity of this pyind derivative, and they achieved en-
hanced activity and selectivity of the biologically active cen-
tre by modifying the distant ruthenium’s ligand sphere. The
promising idea of using such inert complexes within organic
molecules is new[21] and supports the application of spe-
cially tailored chelate ligands such as Hpyind. In detail,
such an anionic pyind-type ligand can form stable com-
Scheme 2. Formation of rhodium and iridium complexes 1 and 2;
a
b
toluene, NaN(SiMe3)2, 60 °C; CH2Cl2, NEt3, 25 °C.
plexes with highly charged central atoms better than similar Scheme 3. Synthesis of ruthenium complex 3.
neutral ligands. It also leaves more space for varying the co-
ligands at the metal centre than most neutral and anionic
polydentate ligands and can easily be modified at several
positions. We have therefore investigated the reactivity of
rhenium(I), ruthenium(II), rhodium(III) and iridium(III)
precursor complexes towards Hpyind in the presence of an
appropriate base.
Results and Discussion
In the synthesis of the complexes reported here, we first
use a strong amide base or potassium hydride for the depro-
tonation of Hpyind in a nonprotic solvent to which we then
add the precursor complex. The synthetic strategy shown in
Scheme 2 for the rhodium complex 1 works well, although
the stoichiometry of the amide has to be strictly controlled
as some side-reactions may occur when excess base is pres-
Scheme 4. Formation of complexes 4 and 5.
The isolated complexes 1–3 are stable under argon at
ent. We further established that even weak bases such as room temperature. However, some decomposition can be
triethylamine are capable of quantitatively abstracting the observed in moist air after several days. Solutions of these
proton of Hpyind when it is acidified by pre-coordination complexes in dichloromethane are stable for days, whereas
of the precursor complex to the pyridine ring (Scheme 3). the addition of methanol or moisture leads to the appear-
The resulting triethylammonium halide is easily precipitated ance of several new signals in the NMR spectra and decom-
from toluene or separated from the product by extraction position. Complex 5 is somewhat more sensitive, and its
into a small amount of ethanol. Only one product was ob- decomposition is indicated by the formation of an intense
tained in the reactions of RuII, RhIII and IrIII, whereas the green colour after a few seconds when the complex is ex-
ReI complex 5 required purification by flash chromatog- posed to moist air. All of the complexes show a high ther-
raphy in a dry and oxygen-free environment. We were un- mal stability, which makes them suitable for direct mass
able to obtain an analytically pure sample of complex 4 spectrometry.
from the reaction of [Re(CO)5Br] with Hpyind and NaN-
The 1H NMR spectrum of Hpyind has been described in
(SiMe3)2 or NEt3. The result of this reaction is summarised the literature[4] but we have found some minor errors in the
in Scheme 4. Complex 4, which contains an Re(CO)4 moi- previous assignment concerning H3Ј, H4Ј, H4 and H6Ј. We
ety, is likely to be less stable than 5, which is stabilised by therefore conducted H,H-COSY and HMQC measure-
the bulky axial PPh3 groups. The IR spectrum of 4 supports ments for both Hpyind and complex 1 in order to better
a pseudo-C2v symmetry and shows four ν(C=O) absorp- understand the effect of complexation. These 2D NMR
tions at 2015, 1936, 1912 and 1891 cm–1. Upon evaporation spectra of Hpyind and 1 are given as Supporting Infor-
of toluene, or in a more polar solvent like acetone, only two mation. Upon complexation, the NH signal of Hpyind dis-
frequencies are observed [2011 and 1892 cm–1 (br.)], thus appears completely, the signals of H5 and H6 are shifted
suggesting a fac-Re(CO)3 species. The DEI mass spectrum upfield by about 0.2 ppm, while those of H5Ј, H6Ј and H7
shows only an [Re(CO)3(pyind)]+ fragment as the highest remain largely unaffected in complexes 1–3. The signal of
peak.
H3 is affected only in the iridium complex 2, where it is
Eur. J. Inorg. Chem. 2007, 472–480
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473

B. Neumann, C. Krinninger, I.-P. Lorenz
FULL PAPER
shifted upfield by 0.1 ppm. Complex 5 shows a different Table 1. UV absorption data for pyind complexes in CH2Cl2.
picture due to the lower metal oxidation state, because the
λmax [nm]
λmax [nm]
λmax [nm]
(ε [–1 cm–1])
(ε [–1 cm–1])
(ε [–1 cm–1])
phosphane ligands are more electron-donating and the pro-
tons of pyind are affected by the phenyl groups of PPh3
(ring current). The signals of the pyridine ring protons are
shifted upfield by about 1.1 ppm on average, thereby indi-
cating a highly electron-enriched aromatic system. All com-
plexes give nearly identical peaks for the C–H carbon atoms
in the 13C NMR spectra, with C7, which shows a 5 ppm
downfield shift, being the only significantly shifted signal.
1
2
3
5
363 (15890)
377 (14620)
374 (11670)
367 (11335)
314 (9000)
326 (10800)
331 (9860)
323 (11430)
260 (16680)
260 (15240)
248 (14760)
As several structure-related questions about Hpyind have
The four quaternary carbon signals are shifted downfield, been discussed in the literature, we were surprised to find
by about 7 ppm for C1Ј, about 10 ppm for C2 and C7A and that the crystal structure was unknown. In these studies,
about 3 ppm for C3A, in all complexes. This effect is well bridging methylene chains have been attached to restrain
known for metallacycle carbon atoms but somewhat sur- the nitrogen atoms in a cis conformation,[4] and tautomeric
prising for the other ones. To conclude, the main effect of forms upon N-methylation have been studied.[26] After
complexation is observed at the benzene ring of the indole recrystallisation from chloroform/hexane we obtained
moiety, and no major change is expected in the pyridylpyr- colourless single crystals of Hpyind. An ORTEP plot of the
role moiety.
molecular structure is displayed in Figure 1, which shows
The mass spectra show no unexpected behaviour and are that Hpyind exists in a cis conformation in the solid state.
easily interpreted as a result of the metal and halide isotope The indole and pyridyl moieties are somewhat twisted by
distribution. The main fragmentation pattern is given by about 14°, as shown by the dihedral angle N(1)–C(1)–C(9)–
splitting off the ligands one after another.
N(2) given in Table 2. Within the crystal, two Hpyind mole-
The IR spectra of the complexes show a common strong cules form a dimeric unit where the planes of the two
band at around 1610 cm–1 for ν(C=N) and lack the indole Hpyind molecules form an angle of 110.8°. They are con-
ν(NH) band of Hpyind at 3450 cm–1. The two carbonyl nected by two hydrogen bonds, where H(1) is refined freely
bands of complex 5 indicate the sole presence of the cis between N(1) of one molecule and N(2) of the other mole-
conformation in solution, as was also observed in the crys- cule with an almost ideal N(1)–H(1)–N(2) angle of 170(2)°
tal structure of 5. They appear at very low energy (ν = 1905, and an N(1)–N(2) distance of 2.988(3) Å, which indicates a
˜
1823 cm–1), in the range of terminal carbonyl ligands. Sim- strong interaction. The luminescent beryllium complex of
ilar low frequencies have been reported for anionic complex pyind reported by Liu et al.[16] shows a similar structure.
radicals of rhenium(I).[22]
In order to compare the changes in the pyind moiety on
The electronic spectra of Hpyind have been discussed complexation, some interatomic distances have been sum-
previously.[23–25] On complexation, the absorption maxi- marised in Table 3. In all our complexes the pyind ligand
mum at 325 nm in Hpyind[4] shows a bathochromic shift of becomes planar, with the previously mentioned dihedral an-
40–65 nm. Table 1 shows this effect to be affected by the gle reduced to almost zero. This is accompanied by a sig-
metal’s charge and that it is stronger for complexes contain- nificant shortening of the C(1)–C(9) bond. Together with
ing fifth-row metals than those with fourth-row metals.
these two carbon atoms, the two nitrogen donor atoms and
Figure 1. ORTEP plot (25% probability) of Hpyind. The numbering displayed is used in the discussion of all crystal structures for the
pyind moiety.
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Neutral Complexes of 2-(2Ј-Pyridyl)indole and d6 Transition Metals
Table 2. Selected angles [°] and dihedral angles [°].
FULL PAPER
Hpyind
1
2
3
5
Cl(1)–M(1)–N(1)
Cl(1)–M(1)–N(2)
N(1)–M(1)–N(2)
M(1)–N(1)–C(1)
M(1)–N(2)–C(9)
N(1)–C(1)–C(9)
N(2)–C(9)–C(1)
N(1)–C(1)–C(9)–N(2)
88.55(6)
87.45(5)
76.79(8)
116.6(3)
117.1(3)
115.9(2)
115.0(2)
–3.7(3)
86.69(10)
85.62(10)
76.12(14)
116.07(16)
115.47(16)
115.4(4)
114.1(4)
3.3(5)
87.72(9)
88.70(9)
76.08(12)
114.3(3)
115.3(3)
114.9(3)
113.8(3)
–4.1(5)
74.73(9)
116.20(19)
116.49(19)
117.6(2)
114.9(2)
–2.0(4)
121.28(17)
117.18(17)
–13.8(3)
the metal atom form a coplanar five-membered metallacy-
cle. The pyind ligand has quite a small bite angle of 74–77°,
which makes it a nonideal ligand for large atoms. As it fits
well into the octahedral coordination geometry of d6 com-
plexes, this deficiency seems to be compensated for by its
charge transfer to the metal centre.
differences should be emphasised. The C(9)–N(2) distance
increases in all complexes relative to the noncoordinated
Hpyind ligand, but it remains unchanged in complex 2.
This is in agreement with the shorter metal–ligand contacts
and the shorter C(1)–C(9) distance observed. As the RhIII
centre in complex 1 should be smaller than RuII in complex
3 (Figure 4), the latter would be expected to show larger
metal–ligand distances. This is true for the slightly larger
N(1)–Ru(1) distance, although the N(2)–Ru(1) distance is
shortened by 0.05 Å. On the contrary, the shorter distances
in complex 2 along with the shorter distances in the metall-
acycle mean that the ruthenium metallacycle of 3 has larger
intraligand distances than found in 1.
Table 3. Selected interatomic distances [Å].
Hpyind
1
2
3
5
M(1)–N(1)
M(1)–N(2)
M(1)–Cl(1)
2.073(2)
2.1343(19) 2.103(3)
2.3987(8) 2.3860(12) 2.4142(10)
2.050(3)
2.082(3)
2.108(3)
2.153(2)
2.202(2)
N(1)–C(1) 1.372(3)
C(1)–C(9) 1.458(3)
C(9)–N(2) 1.342(3)
1.375(3)
1.440(4)
1.355(3)
1.378(5)
1.421(6)
1.342(5)
1.382(4)
1.446(6)
1.366(5)
1.382(4)
1.427(4)
1.368(4)
When complex 5 (Figure 5) is considered, the different
co-ligand situation in this complex compared to the other
complexes has to be taken in account. The two axial phos-
phane ligands show virtually identical Re–P distances of
The RhIII complex 1 (Figure 2) and the IrIII complex 2
(Figure 3) are very similar, as would be expected, but some
Figure 2. Molecular structure of rhodium complex 1 (25% probability). The methyl protons of C5Me5 are omitted for clarity.
Eur. J. Inorg. Chem. 2007, 472–480
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475

B. Neumann, C. Krinninger, I.-P. Lorenz
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Figure 3. Molecular structure of complex 2 (25% probability). The methyl protons of C5Me5 are omitted.
Figure 4. ORTEP plot of complex 3 (25% probability). The 18 disordered protons of the hexamethylbenzene moiety are omitted and a
solvent molecule of CH2Cl2 is not included in the diagram.
2.4273(9) and 2.4324(9) Å, respectively, and all of the P– both σ-donors and π-acceptors, are found in the trans posi-
C distances of the phenyl groups lie between 1.832(3) and tions with respect to the nitrogen donors. The very low
1.837(3) Å. Two linear carbonyl ligands, which can act as C=O valence vibration energy observed suggests these car-
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Neutral Complexes of 2-(2Ј-Pyridyl)indole and d6 Transition Metals
FULL PAPER
NMR spectra were measured with a Jeol Eclipse 270, Jeol Eclipse
400 or Jeol EX 400 spectrometer; the chemical shifts are given rela-
tive to external standards (TMS and 85% H3PO4). Mass spectra
were recorded with a Jeol MStation JMS 700. IR spectra were re-
corded from KBr pellets or solutions in an NaCl cell using a Per-
kin–Elmer Spectrum One FT-IR spectrometer. UV/Vis spectra
were measured in glass cuvettes with a Perkin–Elmer Lambda 16
spectrometer. The melting points, obtained with a Büchi 510 appa-
ratus, are uncorrected. Elemental analysis was performed by the
Microanalytical Laboratory of the Department of Chemistry and
Biochemistry, LMU, using a Hereaus Elementar Vario El appara-
tus.
bonyl groups absorb a considerable amount of electron den-
sity. The low-valent rhenium(I) centre is larger than the op-
timum size for a chelating pyind ligand. Both of the Re–N
distances are 0.10 Å longer than in the iridium complex 2.
However, the ligand shows both a shortened C(1)–C(9)
bond, as was observed in compound 2, as well as longer
C=N bonds, as in 3.
2-(2Ј-Pyridyl)indol (Hpyind): This compound was prepared accord-
ing to the procedure reported by Thummel[4] and recrystallised
from chloroform/hexanes. The following NMR assignments differ
slightly from the literature. The 2D NMR spectra are given as Sup-
porting Information. 1H NMR (400 MHz, CD2Cl2, 25 °C): δ =
3
4
5
9.79 (s, 1 H, NH), 8.57 (ddd, JH,H = 5.2, JH,H = 1.6, JH,H
=
1.0 Hz, 1 H, H3Ј), 7.82 (dt, 3JH,H = 8.0,
J
= 1.0 Hz, H6Ј), 7.73
H,H
4,5
(td, JH,H = 8.0, JH,H = 1.6 Hz, H5Ј), 7.62 (dd, JH,H = 8.0, JH,H
3
4
3
4
= 1.0 Hz, H4), 7.38 (dd, JH,H = 8.0, JH,H = 1.0 Hz, H7), 7.18 (td,
3
4
3JH,H = 8.0, 4JH,H = 1.0 Hz, 1 H, H6), 7.18 (ddd, 3JH,H = 8.0, 3JH,H
= 5.2, JH,H = 1.0 Hz, H4Ј), 7.08 (td, JH,H = 8.0, JH,H = 1.0 Hz,
4
3
4
4
5
1 H, H5), 7.02 (dd, JH,H = 2.0, JH,H = 1.0 Hz, 1 H, H3) ppm. 13
C
NMR (100.62 MHz, CD2Cl2, 25 °C): δ = 150.3 (C1Ј), 149.2 (C3Ј),
136.9 (C2), 136.7 (C5Ј), 136.6 (C7A), 129.2 (C3A), 123.1 (C6), 122.1
(C4Ј), 121.1 (C4), 120.1 (C5), 119.9 (C6Ј), 111.4 (C7), 100.3 (C3)
ppm.
Chlorido(η5-pentamethylcyclopentadienido)[2-(2Ј-pyridyl)indolido-
N,NЈ]rhodium(III) (1): A 1  solution of NaN(SiMe3)2 (280 µL,
0.28 mmol) was added to a solution of Hpyind (54 mg, 0.28 mmol)
in toluene (10 mL). The mixture was stirred for 15 min and a solu-
tion of [Rh2Cl4Cp*2] (85 mg, 0.14 mmol) in toluene (20 mL) was
added dropwise. The red solution became darker and was stirred
at 60 °C; after 10 min, an orange precipitate had formed. After
60 min, precipitation was complete and complex 1 was filtered,
washed with cold toluene and dried in vacuo (115 mg, 0.25 mmol,
Figure 5. ORTEP plot of the rhenium compound 5 (25% prob-
ability). Only the terminal carbon atoms of both axial tri-
phenylphosphane ligands are displayed. One disordered molecule
of toluene is omitted.
1
3
89%). H NMR (400 MHz, CD2Cl2, 25 °C): δ = 8.54 (br. d, JH,H
Conclusion
3
4
4
= 5.7 Hz, 1 H, H3Ј), 7.76 (ddd, JH,H = 8.1, JH,H = 1.7, JH,H
=
=
0.8 Hz, 1 H, H6Ј), 7.71 (ddd, JH,H = 8.1, JH,H = 7.0, JH,H
3
3
4
We have synthesised a series of novel transition metal
complexes with the bidentate amido–imine ligand 2-(2Ј-pyr-
idyl)indole. This is the first study to compare the properties
that arise when different central atoms are used to form
amido–imine complexes. Work on related anionic bidentate
ligands, such as further modified amido–imine ligands and
amido–phosphane ligands, is currently in progress. In ad-
dition, complexes containing different oxidation states for
1.5 Hz, 1 H, H5Ј), 7.57 (dt, JH,H = 7.9, JH,H = 1.1 Hz, 1 H, H4),
3
4
3
4,5
3
7.39 (dq, JH,H = 8.2,
J
H,H
= 1.0 Hz, 1 H, H7), 7.14 (ddd, JH,H
= 7.0, JH,H = 5.7, JH,H = 1.7 Hz, 1 H, H4Ј), 7.04 (ddd, JH,H
=
3
4
3
8.2, 3JH,H = 6.8, 4JH,H = 1.1 Hz, 1 H, H6), 7.00 (d, 4JH,Rh = 1.1 Hz,
3
3
4
1 H, H3), 6.88 (ddd, JH,H = 7.9, JH,H = 6.8, JH,H = 1.0 Hz, 1 H,
H5), 1.62 (s, 15 H, Cp*) ppm. 13C NMR (100.52 MHz, CD2Cl2,
25 °C): δ = 157.4 (C1Ј), 150.3 (C3Ј), 145.8 (C2), 144.9 (C7A), 137.8
(C5Ј), 132.5 (C3A), 121.8 (C4), 121.6 (C4Ј), 120.9 (C6), 119.8 (C6Ј),
the central atoms, especially d8 systems such as RhI, IrI and 117.7 (C5), 115.3 (C7), 101.2 (C3), 94.6 (d, JC,Rh = 7.7 Hz, Cp*),
1
9.4 (s, Cp*) ppm. DEI-MS (70 eV): m/z (%) = 466 (10) [M+], 431
(100) [M+ – Cl], 237 (17) [RhCp* – H], 235 (15) [RhCp* – 3 H],
PdII, will also be investigated. Investigations into the cata-
lytic activity and optimisation of these complexes to im-
prove certain catalytic processes are also underway.
194 (13) [pyind]. IR (KBr) ν = 3047 (w), 2984 (w), 2914 (w), 1607
˜
(s), 1536 (s), 1449 (s), 1350 (m), 1310 (m), 1271 (w), 1199 (w), 1156
(m), 1119 (w), 1019 (m), 763 (s), 753 (m) cm–1; (CH Cl ) ν = 3049
˜
2
2
(m), 2978 (w), 2918 (w), 1608 (s), 1537 (s), 1453 (s), 1361 (m), 1350
(m), 1312 (m), 1262 (m), 1200 (w), 1154 (m), 1141 (w), 1118 (w),
1077 (w), 1023 (m), 963 (w) cm–1. UV/Vis (CH2Cl2, 25 °C): λ (ε) =
363 (15890), 314 (9000), 260 (16680 –1 cm–1) nm. C23H24ClN2Rh
(466.81): calcd. C 59.18, H 5.18, N 6.00; found C 58.57, H 5.24, N
5.88. M.p. 305 °C (dec.). Single crystals suitable for X-ray structure
determination were obtained by diffusion of pentane into a solu-
tion of 1 in CH2Cl2.
Experimental Section
General: All reactions were carried out under argon using standard
Schlenk and vacuum-line techniques. Solvents were purified by
standard procedures; dichloromethane was distilled from calcium
hydride. The complexes [RhCl2Cp*]2,[27] [IrCl2Cp*]2,[27] [Ru(CO)2-
[29]
ClCp*],[28] [Ru(C6Me6)Cl2]2
and [Re(CO)5Br][30] and Hpyind[4]
were prepared and purified according to literature procedures.
Eur. J. Inorg. Chem. 2007, 472–480
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
477

B. Neumann, C. Krinninger, I.-P. Lorenz
FULL PAPER
Chlorido(η5-pentamethylcyclopentadienido)[2-(2Ј-pyridyl)indolido-
fusion of pentane into a solution of 3 in CH2Cl2. They contain one
N,NЈ]iridium(III) (2): Hpyind (59 mg, 0.3 mmol) and [Ir2Cl4Cp*2] molecule of CH2Cl2 per formula unit.
(120 mg, 0.15 mmol) were dissolved in CH2Cl2 (5 mL) and NEt3
Tetracarbonyl[2-(2Ј-pyridyl)indolido-N,NЈ]rhenium(I) (4): Hpyind
(42 µL, 0.4 mmol) was added. After stirring at room temp. for 48 h,
the solvent was evaporated. The yellow residue was stirred with
EtOH (3ϫ5 mL) to remove HNEt3Cl and the slightly yellow solu-
tion was discarded after centrifugation. Drying in vacuo yielded 2
(97 mg, 0.5 mmol) was dissolved in toluene (10 mL) and a solution
of [Re(CO)5Cl] (181 mg, 0.5 mmol) in toluene (10 mL) was added.
A 0.1  solution of NaN(SiMe3)2 in toluene (5.0 mL) or NEt3
(75 µL, 0.5 mmol) was then added and the mixture stirred at 50 °C.
Concentration of the solution after 16 h yielded a blue-green solid
that dissolved readily in acetone or CH2Cl2. All our attempts to
crystallise the substance by diffusion of a non-polar solvent into a
solution of 4 or by cooling were not successful. NMR signals in
the aromatic region are broad and could not be unambiguously
interpreted. DEI-MS (70 eV): m/z (%) = 464 (89) [M+ – CO], 436
(50) [M+ – 2 CO], 408 (53) [M+ – 3 CO], 380 (100) [Re(pyind)], 353
1
(135 mg, 0.24 mmol, 81%). H NMR (400 MHz, CD2Cl2, 25 °C):
3
3
δ = 8.55 (d, JH,H = 5.8 Hz, 1 H, H3Ј), 7.81 (d, JH,H = 8.2 Hz, 1
H, H6Ј), 7.70 (t, 3JH,H = 8.1 Hz, 1 H, H5Ј), 7.54 (d, 3JH,H = 8.0 Hz,
1 H, H4), 7.37 (d, JH,H = 8.4 Hz, 1 H, H7), 7.09 (dd, JH,H = 6.5,
3
3
3JH,H = 5.8 Hz, 1 H, H4Ј), 7.01 (dd, JH,H = 8.4, JH,H = 6.8 Hz, 1
3
3
H, H6), 6.91 (s, 1 H, H3), 6.90 (dd, JH,H = 7.8, JH,H = 6.8 Hz, 1
H, H5), 1.66 (s, 15 H, Cp*) ppm. 13C NMR (100.52 MHz, CD2Cl2,
25 °C): δ = 158.1 (C1Ј), 150.4 (C3Ј), 145.3 (C2), 144.9 (C7A), 138.1
(C5Ј), 131.5 (C3A), 122.1 (C4 and C4Ј), 121.7 (C6), 119.6 (C6Ј), 118.1
(C5), 115.2 (C7), 101.8 (C3), 86.8 (Cp*), 9.6 (Cp*) ppm. DEI-MS:
m/z (%) = 556 (65) [M+], 521 (100) [M+ – Cl], 363 (20) [IrCp*Cl],
3
3
(25) [Re(pyind) – HCN]. IR (toluene) ν = 2015 (vs), 1936 (m), 1912
˜
(vs), 1891 (vs) cm–1; (acetone) ν = 2011 (vs), 1892 (vs) cm–1; (tolu-
˜
ene, from NEt run) ν = 2010 (vs), 1891 (vs) cm–1. Further details
˜
3
of the characterisation are not available.
323 (17) [Ir(C H )Cl]. IR (KBr) ν = 3052 (w), 2986 (w), 1609 (s),
˜
7
11
1541 (s), 1491 (w), 1447 (s), 1371 (w), 1349 (m), 1311 (m), 1266
(w), 1203 (w), 1155 (m), 1122 (m), 1082 (w), 1022 (m), 965 (w), 769
Dicarbonyl[2-(2Ј-pyridyl)indolido-N,NЈ]bis(triphenylphosphane)-
rhenium(I) (5): Hpyind (39 mg, 0.2 mmol), [Re(CO)5Br] (81 mg,
0.2 mmol), PPh3 (106 mg, 0.4 mmol) and NEt3 (31 µL, 0.22 mmol)
were dissolved in toluene (5 mL) and stirred in a sealed Schlenk
tube at 100 °C for 48 h. The hot yellow-brown solution was sepa-
rated from the colourless precipitate (HNEt3Cl). The IR spectrum
shows several carbonyl bands, thereby indicating that a mixture of
species is present. The solution was cooled to –32 °C overnight and
a yellow precipitate formed. This was separated (80 mg, 42%) from
the solution and purified using a short chromatography column
[SiO2 60, 70–230 mesh, 250 mL (!) CH2Cl2]. An air- and moisture-
free environment must be maintained during the entire workup pro-
cess as the crude product easily decomposes to form an intensely
green oil, whereas the final pure product is considerably more
stable. Drying yielded 5 as a yellow solid (70.2 mg, 73 µmol, 37%).
1H NMR (400 MHz, CD2Cl2, 25 °C): δ = 7.64–7.66 (m, 1 H, H4),
(s), 753 (s), 517 (w), 443 (w), 376 (w) cm–1; (CH Cl ) ν = 3047 (w),
˜
2
2
2978 (w), 2921 (w), 1612 (s), 1453 (s), 1450 (s), 1381 (w), 1360 (w),
1359 (m), 1314 (m), 1202 (w), 1155 (w), 1120 (w), 1080 (w), 1030
(m) cm–1. UV/Vis (CH2Cl2, 25 °C): λ (ε) = 377 (14620), 326 (10800),
260 (15240), 226 (24740 –1 cm–1) nm. C23H24ClIrN2 (556.12):
calcd. C 49.67, H 4.35, N 5.04; found C 49.43, H 4.15, N 4.90.
M.p. 305–307 °C (dec.). Single crystals suitable for X-ray structure
analysis were obtained by diffusion of pentane into a solution of 2
in CH2Cl2.
Chlorido(hexamethylbenzene)[2-(2Ј-pyridyl)indolido-N,NЈ]-
ruthenium(II) (3): Hpyind (78 mg, 0.4 mmol) and [Ru2Cl4(C6-
Me6)2] (134 mg, 0.2 mmol) were dissolved in CH2Cl2 (10 mL) and
NEt3 (30 µL, 0.4 mmol) was added. After stirring at room temp.
for 24 h, the NMR spectrum indicated quantitative reaction. The
solution was concentrated in vacuo and the residue was stirred with
a small amount of EtOH (2 ϫ 3 mL) to remove HNEt3Cl. The
EtOH solution was discarded after centrifugation from the insolu-
ble residue, which was dried to give 3 as a yellow to orange powder
3
3
4
7.46 (br. d, JH,H = 5.2 Hz, H3Ј), 7.15 (dd, JH,H = 7.2, JH,H
=
=
3
3
4
1.2 Hz, 1 H, H7), 7.12 (ddd, JH,H = 8.0, JH,H = 7.2, JH,H
1.2 Hz, H6), 7.08–7.11 (m, 18 H, PPh3), 6.99–7.01 (m, 12 H, PPh3),
6.97–6.98 (m, 1 H, H5), 6.85 (d, JH,H = 1.0 Hz, H3), 6.63 (dd,
4
3JH,H = 6.0, JH,H = 5.2 Hz, 1 H, H4Ј), 6.63 (d, JH,H = 7.4 Hz, 1
3
3
1
(153 mg, 0.31 mmol, 78%). H NMR (270 MHz, CD2Cl2, 25 °C):
H, H6Ј), 6.00 (ddd, JH,H = 7.4, JH,H = 6.0, JH,H = 1.6 Hz, 1 H,
3
3
4
3
4
5
δ = 8.49 (ddd, JH,H = 5.8, JH,H = 1.4, JH,H = 1.0 Hz, 1 H, H3Ј),
H5Ј) ppm. 13C NMR (100.63 MHz, CD2Cl2, 25 °C): δ = 156.9 (C1Ј),
7.65 (ddd, 3JH,H = 8.2, 4JH,H = 2.4, 5JH,H = 1.0 Hz, 1 H, H6Ј), 7.62
151.6 (C3Ј), 147.8 (C2), 145.9 (C7A), 135.3 (C5Ј), 133.5 (t, JC,P
=
(ddd, JH,H = 8.2, JH,H = 6.5, JH,H = 1.4 Hz, 1 H, H5Ј), 7.53 (dt,
3
3
4
5.3 Hz, PPh3), 132.2 (C3A), 129.1 (PPh3), 127.7 (t, JC,P = 4.3 Hz,
PPh3), 120.49 (C4), 120.47 (C4Ј), 120.0 (C6), 118.6 (C6Ј), 117.8 (C5),
117.1 (C7), 101.4 (C3) ppm. 31P NMR (162.00 MHz, CD2Cl2,
25 °C): δ = 21.05 ppm. DEI-MS (70 eV): m/z (%) = 960 (7) [M+],
698 (5) [M+ – PPh3], 642 (9) [Re(PPh3)(pyind)], 262 (100) [PPh3],
3JH,H = 8.1, 4JH,H = 1.0 Hz, 1 H, H4), 7.30 (dq, 3JH,H = 8.4,
J
H,H
4,5
= 1.0 Hz, 1 H, H7), 7.06 (td, JH,H = 6.5, JH,H = 5.8, JH,H
=
=
3
3
4
2.4 Hz, 1 H, H4Ј), 7.00 (ddd, JH,H = 8.4, JH,H = 6.8, JH,H
3
3
4
1.4 Hz, 1 H, H6), 6.94 (d, 4JH,H = 0.8 Hz 1 H, H3), 6.87 (ddd, 3JH,H
= 7.8, JH,H = 6.8, 4JH,H = 1.1 Hz, 1 H, H5), 1.98 (s, 18 H, C6Me6)
3
183 (45) [PPh ]. IR (KBr) ν = 1905 (vs), 1823 (vs), 1609 (m), 1533
˜
2
ppm. 13C NMR (67.9 MHz, CD2Cl2, 25 °C): δ = 157.5 (C1Ј), 151.9
(C3Ј), 146.6 (C2), 144.3 (C7A), 137.0 (C5Ј), 132.3 (C3A), 121.6 (C4),
120.7 (C4Ј), 120.1 (C6), 118.9 (C6Ј), 117.6 (C5), 116.0 (C7), 101.2
(C3), 93.1 (C6Me6), 15.8 (C6Me6) ppm. FAB-MS: m/z (%) = 493
(m), 1481 (m), 1455 (w), 1444 (m), 1432 (s), 1367 (w), 1349 (w),
1318 (w), 1263 (w), 1153 (w), 1091 (m), 741 (s), 694 (s), 613 (w),
518 (s), 413 (w) cm–1. UV/Vis (CH2Cl2, 25 °C) λ (ε) = 367 (11335),
323 (11430 –1 cm–1) nm. C51H39N2O2P2Re (960.02): calcd. C
63.81, H 4.09, N 2.92; found C 59.19, H 3.86, N 2.56. M.p. 211–
214 °C (dec.). Single crystals suitable for X-ray structure determi-
nation were obtained from the initial toluene solution after separat-
ing the HNEt3Cl and cooling from 100 °C to room temp. within
10 h. The yellow, block-shaped crystals contain one molecule of
toluene per formula unit.
(25) [MH+], 492 (28) [M+], 457 (100) [M+ – Cl]. IR (KBr) ν = 3039
˜
(w), 1605 (s), 1532 (s), 1446 (s), 1383 (w), 1360 (w), 1347 (m), 1309
(s), 1261 (m), 1226 (w), 1150 (w), 1115 (w), 1071 (m), 1036 (m),
1020 (m), 782 (m), 769 (m), 748 (m), 517 (w), 456 (w), 373 (w)
cm–1; (CH Cl ) ν = 3052 (m), 2977 (w), 2923 (w), 1608 (s), 1534
˜
2
2
(s), 1447 (s), 1386 (w), 1361 (w), 1348 (m), 1312 (m), 1199 (w), 1153
(w), 1118 (w), 1075 (w), 1021 (m), 960 (w), 895 (w) cm–1. UV/Vis
(CH2Cl2, 25 °C): λ (ε) = 374 (11670), 331 (9860), 248 (14760), 229
(20135 –1 cm–1) nm. C25H27ClN2Ru (492.02): calcd. C 61.03, H
5.53, N 5.69; found C 58.30, H 5.58, N 5.34. M.p. Ͼ320 °C. Single
crystals suitable for X-ray structure analysis were obtained by dif-
X-ray Crystallography: X-ray crystallographic data (Table 4) were
collected with a Nonius Kappa CCD and with an Oxford Diffrac-
tion Xcalibur S, both using graphite-monochromated Mo-Kα radia-
tion (λ = 0.71073 Å). Structures were solved by direct methods with
478
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 472–480

Neutral Complexes of 2-(2Ј-Pyridyl)indole and d6 Transition Metals
Table 4. Crystallographic data of Hpyind as well as complexes 1–3 and 5.
FULL PAPER
Hpyind
1
2
3
5
Empirical formula
Formula mass [amu]
C13H10N2
194.232
200(2)
0.71073
tetragonal
P41212
8.4513(12)
8.4513(12)
29.236(6)
90
C23H24ClN2Rh
466.808
200(2)
0.71073
monoclinic
P21/n
8.2365(16)
14.495(3)
16.534(3)
90
C23H24ClIrN2
556.120
200(2)
0.71073
monoclinic
P21/n
8.2178(16)
14.302(3)
16.432(3)
90
C26H29Cl3N2Ru
576.95
200(2)
0.71073
orthorhombic
Pbca
8.5237(17)
19.500(4)
29.512(6)
90
C58H47N2O2P2Re
1052.161
200(2)
0.71073
monoclinic
P21/c
12.278(3)
20.144(4)
19.284(4)
90
Temperature [K]
Wavelength [Å]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
90
90
2088.2(6)
8
1.2356(4)
0.075
95.75(3)
90
1964.0(7)
4
1.5787(6)
1.016
96.35(3)
90
1919.4(7)
4
1.9245(7)
7.106
1080
90
90
95.97(3)
90
4743.7(17)
4
1.4733(5)
2.675
2120
γ [°]
V [Å3]
4905.1(17)
8
1.5626(5)
0.984
Z
Dcalcd. [g cm–1
]
µ (Mo-Kα) [mm–1
F(000)
]
816
952
2352
Crystal size [mm]
θ range [°]
Index ranges
0.24ϫ0.16ϫ0.09
3.19–25.03
–10 Յ h Յ 10
–7 Յ k Յ 7
–28 Յ l Յ 34
3522
0.45ϫ0.25ϫ0.18
3.21–26.02
–10 Յ h Յ 9
–17 Յ k Յ 17
–20 Յ l Յ 20
24467
0.40ϫ0.1ϫ0.05
4.01–30.07
–11 Յ h Յ 11
–20 Յ k Յ 20
–23 Յ l Յ 23
25780
0.18ϫ0.09ϫ0.04
3.25–25.11
–10 Յ h Յ 10
–23 Յ k Յ 23
–34 Յ l Յ 35
8110
0.14ϫ0.09ϫ0.02
3.21–26.02
–15 Յ h Յ 15
–24 Յ k Յ 24
–23 Յ l Յ 23
18157
Reflections collected
Independent reflections
R(int)
1833
0.0169
3848
0.0466
5620
0.0407
4328
0.0302
9318
0.0224
Completeness to θ
Refinement method
99.2%
99.6%
99.7%
98.9%
Full-matrix
99.6%
Full-matrix
least squares on F2
1833/0/166
1.069
R1 = 0.0411
wR2 = 0.1101
R1 = 0.0550
wR2 = 0.1184
–
Full-matrix
least squares on F2
3848/0/249
1.044
R1 = 0.0254
wR2 = 0.0620
R1 = 0.0322
wR2 = 0.0652
–
Full-matrix
Full-matrix
least squares on F2
9318/0/614
1.062
R1 = 0.0259
wR2 = 0.0549
R1 = 0.0352
wR2 = 0.0582
–
least squares on F2 least squares on F2
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices
[I Ͼ 2σ(I)]
R indices
5620/0/244
1.099
4328/0/289
1.041
R1 = 0.0340
wR2 = 0.0768
R1 = 0.0471
wR2 = 0.0828
–
R1 = 0.0368
wR2 = 0.0858
R1 = 0.0621
wR2 = 0.0954
–
(all data)
Absolute structure parameter
Largest difference peak/hole [eÅ–3
]
0.089/–0.136
0.933/–0.643
3.496/–0.930
0.830/–0.643
1.184/–0.812
the SHELXS[31] program and refined by full-matrix least-squares
with SHELXL-97.[31] CCDC-616194 (Hpyind), -616193 (1),
-616192 (2), -616195 (3) and -616196 (5) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from the Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
[10]
D. Karshtedt, A. T. Bell, T. D. Tilley, Organometallics 2004, 23,
4169–4171.
G. Cravotto, F. Demartin, G. Palmisano, A. Penoni, T. Radice,
S. Tollari, J. Organomet. Chem. 2005, 690, 2017–2026.
M. Scheibitz, J. B. Heilmann, R. F. Winter, M. Bolte, J. W. Bats,
M. Wagner, Dalton Trans. 2005, 159–170.
J. E. Lee, G. C. Choi, B. O. Rim, S. M. Kim, N. G. Park, Y. K.
Ha, Y. S. Kim, Mater. Sci. Eng. C 2004, 24, 269–273.
W. L. Jia, Q. D. Liu, R. Wang, S. Wang, Organometallics 2003,
22, 4070–4078.
Q. D. Liu, L. Thorne, I. Kozin, D. Song, C. Seward, M.
D’Iorio, Y. Tao, S. Wang, J. Chem. Soc., Dalton Trans. 2002,
3234–3240.
S. F. Liu, Q. Wu, H. L. Schmider, H. Aziz, N. X. Hu, Z. Po-
povic, S. Wang, J. Am. Chem. Soc. 2000, 122, 3671–3678.
H. Bregman, D. S. Williams, E. Meggers, Synthesis 2005, 9,
1521–1527.
D. S. Williams, G. E. Atilla, H. Bregman, A. Arzoumanian,
P. S. Klein, E. Meggers, Angew. Chem. Int. Ed. 2005, 44, 1984–
1987.
H. Bregman, D. S. Williams, G. E. Atilla, P. J. Carroll, E. Meg-
gers, J. Am. Chem. Soc. 2004, 126, 13594–13595.
H. Bregman, P. J. Carroll, E. Meggers, J. Am. Chem. Soc. 2006,
128, 877–884.
U. Schatzschneider, N. Metzler-Nolte, Angew. Chem. Int. Ed.
2006, 45, 1504–1507.
[11]
[12]
[13]
[14]
[15]
Supporting Information (see footnote on the first page of this arti-
cle): H,H-COSY and HMQC spectra for Hpyind and rhodium(III)
complex 1; dimeric unit of Hpyind within the crystal structure as
additional ORTEP plot.
[1] M. Berthod, G. Mignani, G. Woodward, M. Lemaire, Chem.
Rev. 2005, 105, 1801–1836.
[2] D. S. C. Black, D. C. Craig, N. Kumar, L. C. H. Wong, J.
Chem. Soc., Chem. Commun. 1985, 1172–1173.
[3] B. Chiswell, Inorg. Chim. Acta 1972, 6, 629–634.
[4] R. P. Thummel, V. Hedge, J. Org. Chem. 1989, 54, 1720–1725.
[5] C. Crotti, S. Cenini, B. Rindone, S. Tollari, F. Demartin, J.
Chem. Soc., Chem. Commun. 1986, 784–786.
[6] S. Tollari, S. Cenini, A. Penoni, G. Granata, G. Palmisano, F.
Demartin, J. Organomet. Chem. 2000, 608, 34–41.
[7] F. Wu, C. M. Chamchoumis, R. P. Thummel, Inorg. Chem.
2000, 39, 584–590.
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[8] S. Jena, N. Rath, K. C. Dash, Ind. J. Chem. A 1999, 38, 350–
354.
[9] J. C. Lee, B. Mueller, P. Pregosin, G. P. A. Yap, A. L. Rheing-
old, R. H. Crabtree, Inorg. Chem. 1995, 34, 6295–6301.
S. Frantz, J. Fiedler, I. Hartenbach, T. Schleid, W. Kaim, J.
Organomet. Chem. 2004, 689, 3031–3039.
Eur. J. Inorg. Chem. 2007, 472–480
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
479

B. Neumann, C. Krinninger, I.-P. Lorenz
FULL PAPER
[23] Y. Nosenko, R. P. Thummel, A. Mordzinski, Phys. Chem.
Chem. Phys. 2004, 6, 363–367.
[24] Y. Nosenko, Y. Stepanenko, R. P. Thummel, A. Mordzinski,
Chem. Phys. Lett. 1999, 315, 87–94.
[25] J. Herbich, C. Y. Hung, R. P. Thummel, J. Waluk, J. Am. Chem.
Soc. 1996, 118, 3508–3518.
[26] F. Wu, J. Hardesty, R. P. Thummel, J. Org. Chem. 1998, 63,
4055–4061.
[29] M. A. Bennett, T.-N. Huang, T. W. Matheson, A. K. Smith,
Inorg. Synth. 1982, 21, 74.
[30] G. Brauer, Handbuch der Präparativen Anorganischen Chemie,
vol. 3, 3rd ed., Ferdinand Enke Verlag, Stuttgart, 1981, p.
1951–1952.
[31] G. M. Sheldrick, SHELX-97, University of Göttingen, Ger-
many, 1997.
Received: August 4, 2006
[27] C. White, A. Yates, P. M. Maitlis, Inorg. Synth. 1992, 29, 228.
[28] H. Nagashima, K. Mukai, Y. Shiota, K. Yamaguchi, K. Ara,
T. Fukahori, H. Suzuki, M. Akita, Y. Moro-oka, K. Itho, Or-
ganometallics 1990, 9, 799–807.
Published Online: November 21, 2006
480
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Eur. J. Inorg. Chem. 2007, 472–480