A convenient synthesis of cyclopentadienylgallium-the awakening of a sleeping beauty in organometallic chemistry

Article abstract of DOI:10.1002/ejic.201100672

Solid "GaI" reacts with NaCp to yield (ν⁵- cyclopentadienyl)gallium (GaCp) (1). During the synthesis the side product, CpGa→GaCp₂I (2), with a rare gallium-gallium donor-acceptor bond could be isolated. The reaction of 1 with B(C₆F₅) ₃ affords CpGa→B(C₆F₅)₃ (4). The molecular structures of 2 and 4, which contain the first GaCp moieties, are presented. The convenient synthesis of 1 needs only standard laboratory equipment and certainly opens the door for 1 to become a versatile reagent in organometallic chemistry; awakening the sleeping beauty GaCp nearly twenty years after its initial discovery.

Full text of DOI:10.1002/ejic.201100672

SHORT COMMUNICATION
DOI: 10.1002/ejic.201100672
A Convenient Synthesis of Cyclopentadienylgallium – The Awakening of a
Sleeping Beauty in Organometallic Chemistry
Christian Schenk,[a] Ralf Köppe,[b] Hansgeorg Schnöckel,*[b] and Andreas Schnepf*[c]
Dedicated to Professor Malcolm L. H. Green on the occasion of his 75th birthday
Keywords: Cyclopentadienyl ligands / Gallium / Subvalent compounds / Main group elements / Synthesis design
Solid “GaI” reacts with NaCp to yield (η5-cyclopentadienyl)-
gallium (GaCp) (1). During the synthesis the side product,
CpGaǞGaCp2I (2), with a rare gallium–gallium donor–
acceptor bond could be isolated. The reaction of 1 with
B(C6F5)3 affords CpGaǞB(C6F5)3 (4). The molecular struc-
tures of 2 and 4, which contain the first GaCp moieties, are
presented. The convenient synthesis of 1 needs only stan-
dard laboratory equipment and certainly opens the door for
1 to become a versatile reagent in organometallic chemistry;
awakening the sleeping beauty GaCp nearly twenty years
after its initial discovery.
which was also initially synthesized – like AlCp* – from
metastable GaX solutions (X = Cl, Br, I), has a similar
story. GaCp* is hexameric in the solid state[10] and mono-
meric in the gas phase.[11] However, the chemistry of GaCp*
also just began after a simple way to prepare it was discov-
ered by Jutzi et al. using the reduction of Cp*GaI2 with
potassium.[12] In addition, GaCp* can be obtained by the
even more simple metathesis reaction of LiCp* with solid
“GaI”,[13] a subhalide that is surprisingly easily available by
sonication of a 1:1 mixture of elemental gallium and ele-
mental iodine, as discovered by Green et al. in 1990.[14,15]
After the convenient access to GaCp* was discovered, its
chemistry flourished, leading to fascinating results in clus-
ter chemistry as well as coordination chemistry in recent
years.[16] Hence, only the new simpler approaches without
using complicated synthetic routes (co-condensation tech-
nology) paved the way to the application of these AlI and
GaI compounds as conventional reagents in organometallic
chemistry.
Introduction
The synthesis and structural characterization of
(Cp*Al)4[1] (Cp* = C5Me5) was a milestone in organometal-
lic chemistry,[2] as this organometallic compound was the
very first to contain aluminum in the oxidation state +1.
The synthesis of (Cp*Al)4 was initially performed by using
metastable AlX solutions (X = Cl, Br, I), which are avail-
able by a preparative co-condensation technology;[3,4] there-
fore, a highly sophisticated method had to be applied.[5]
(Cp*Al)4 dissociates to monomers in an equilibrium reac-
tion in solution and in the gas phase; the monomer was
structurally characterized a couple of years later.[6] How-
ever, although monomeric AlCp* is an exciting reagent for
organometallic chemistry, its application was only made
possible by Roesky et al., who discovered the easier syn-
thetic route of reducing Cp*AlCl2 with potassium.[7] From
that point onward, AlCp* became a versatile reagent, lead-
ing to a highly productive chemistry;[8] for example, lately
the ruthenium polyhydride complex with AlCp* moieties
[Cp*RuH2AlCp*]2 could be synthesized by the reaction of
AlCp* with [H2RuCp*].[9] The heavier congener GaCp*,
Results and Discussion
With respect to AlCp* and GaCp*, the sterically less de-
manding compound GaCp (Cp = C5H5) (1) is still a Sleep-
ing Beauty[17] since its discovery nearly twenty years ago, as
it was up to now exclusively available by the reaction of
metastable GaX solutions with, for example, LiCp.[18]
We now found a simpler route to GaCp (1): In a way
similar to the synthetic route used for the synthesis of
GaCp*,[13] we treated solid “GaI” with NaCp in toluene at
low temperatures to obtain a colorless solution of GaCp (1)
after filtration. The presence of 1 in solution was confirmed
[a] School of Chemistry, Monash University,
P. O. Box 23, Victoria 3800, Australia
[b] Institut für Anorganische Chemie, Karlsruher Institut für
Technologie, KIT-Campus Süd,
Postfach 6980, 76049 Karlsruhe, Germany
Fax: +49-721-608-44854
E-mail: hansgeorg.schnoeckel@kit.edu
[c] Institut für Anorganische Chemie, Universität Duisburg-Essen,
Universitätsstrasse 5-7, 45117 Essen, Germany
Fax: +49-201-183-2296
E-mail: andreas.schnepf@uni-due.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201100672.
Eur. J. Inorg. Chem. 2011, 3681–3685
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3681

C. Schenk, R. Köppe, H. Schnöckel, A. Schnepf
SHORT COMMUNICATION
by Raman spectroscopy (262.1 cm–1) and 71Ga NMR spec-
The Ga–Ga bond in 3 (243.7 pm) is thereby 3.2 pm
troscopy (–708.4 ppm), whose results are in accordance shorter than the one in 2, which leads to the unusual situa-
with literature values[18] and DFT calculations.[19,20] How- tion that the ligand with the lower steric demand leads to
ever, we were unable to obtain a molecular structure for the longer Ga–Ga bond, showing that the contacts to the
pure GaCp, as it decomposes upon concentration even at σ-bound ligands at the GaIII center significantly influence
–78 °C. Nevertheless, during attempts to crystallize 1, we the bonding within 2 and 3. The bonding to the η5-bound
gained a few yellow crystals of CpGaǞGaCp2I (2), the first ligand in 3 is thereby affected by the additional contacts,
structurally characterized molecule exhibiting a GaICp which results in a more bent arrangement (Ga–Ga–Cp*cen-
moiety (Figure 1).[21]
angle 137.3°) than the one in the structure of 2 (Ga–
troid
Ga–Cpcentroid angle 169.1°), that is, the bonding between
the Ga atom and the carbon atoms of the Cp ligand in 2 is
closer to an ideal η5 interaction.
These results show that the central metal–metal as well as
the metal–ligand bonds in 2 and 3 can hardly be compared
directly, as secondary interactions strongly influence the ar-
rangement and consequently also the bonding in this sec-
tion of the molecules. However, although the bonding be-
tween the GaI center and the Cp ligand is more ideal in 2
than in 3, compound 2 is not very stable in solution: During
recrystallization experiments with 2 in a few milliliters of
mother solution just a gray precipitate and colorless crystals
of GaCp3 could be obtained even when working at
–30 °C.[25] This result clearly hints to a higher reactivity of
GaCp with respect to GaCp*, which is stable in the solid
state and in solution even at elevated temperatures.[12]
Nevertheless, stable diluted solutions of GaCp (1) might
be of use for further systematical reactions, making 1 a sub-
stance with great potential in the productive and widely
used field of monodentate group 13 ligands. This general
Figure 1. Molecular structure of CpGaǞGaCp2I (2) (thermal ellip-
soids with 50% probability). Selected distances [pm] and angles [°]:
Ga1–Ga2 246.90(17), Ga2–C1 230.5(12), Ga2–C2 229.4(10), Ga2–
C3 224.0(9), Ga2–C4 223.8(11), Ga2–C5 228.6(10), Ga1–C101
204.6(12), Ga1–C205 202.6(10), Ga1–I1 262.52(13), Ga2–Cpcentroid
193.4(1), Ga2–C103 316.6(11), Ga2–C104 324.1(10), Ga2–C202
342.5(11), Ga2–C203 356.6(12); Ga2–Ga1–C101 100.2(3), Ga2–
Ga1–C205 106.1(3), Ga2–Ga1–I1 110.53(6), C101–Ga1–C205
125.1(5), C101–Ga1–I1 110.5(3), C205–Ga1–I1 103.6(3).
Compound 2 crystallizes in the Pca21 space group in the
form of separate molecules, thus no further intermolecular
Ga–Ga or Ga–I contacts are present in the solid state. The
Ga–Ga bond in 2 (246.88 pm) is in the range of a normal
Ga–Ga single bond, although it is better described as a do-
nor–acceptor bond between the Lewis base GaCp and the
Lewis acid GaICp2. Hence, 2 is a rare example of a molecu-
lar compound containing a homonuclear dative bond be-
tween group 13 elements.[22] The hypothetical isomer
Cp2Ga–GaCpI (2Ј), having a normal Ga–Ga bond and
both Ga atoms in the formal oxidation state +2, is less
stable (2Ј Ǟ 2 +35.7 kJ/mol) according to quantum chemi-
cal calculations.[20]
Taking a closer look into the molecular structure of 2
shows additional contacts between the gallium atom in the
formal oxidation state +1 (Ga2) and the σ-bound Cp li-
gands. The Ga–C contacts are between 317 and 366 pm,
which is at the long-range end of Ga–C contacts found in
benzene complexes of GaI, for example, the Ga–C distances
in an (η6-benzene)gallium(I) complex vary between 302 and
330 pm.[23] The formation of additional contacts in 2 is
thereby similar to those, which have been found for the cor-
responding Cp* compound Cp*GaǞGaCp*I2 (3).[24] Due
to the higher steric demand of the Cp* ligands in 3 only one
σ-bound Cp* ligand is present, which also forms additional
contacts to the gallium atom in the oxidation state +1.
Figure 2. Molecular structure of CpGaǞB(C6F5)3 (4) (thermal el-
lipsoids with 25% probability). Selected distances [pm] and angles
[°]: Ga1–B1 215.4(3), Ga1–Cpcentroid 188.4(17), Ga1–C1 220.1(4),
Ga1–C2 224.4(4), Ga1–C3 226.0(4), Ga1–C4 223.0(3), Ga1–C5
219.6(4), Ga1–F102 289.5(6), Ga1–F202 294.0(8), Ga1–F302
304.8(9), B1–C101 163.6(4), B1–C201 164.9(4), B1–C301 161.0(4);
B1–Ga1–Cpcentroid 170.12(7), Ga1–B1–C101 105.53(16), Ga1–B1–
C201 100.91(16), Ga1–B1–C301 103.61(15), C101–B1–C201
111.91(19), C201–B1–C301 116.1(2), C101–B1–C301 116.4(2),
Σ°CBC 344.4(2).
3682
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Eur. J. Inorg. Chem. 2011, 3681–3685

A Convenient Synthesis of Cyclopentadienylgallium
Table 1. Selected distances [pm] and angles [°] for 2, 3, 4, and 5 (E = B, Ga; Cpa = Cp, Cp*).
a
a
Compound
Ga–Cpa
Ga–E
Ga–CCp
Ga–CCp
(av.)
Σ°CBC
E–Ga–Cpa
centroid
centroid
(min–max)
CpGaǞGaCp2I (2)
Cp*GaǞGaCp*I2 (3)
CpGaǞB(C6F5)3 (4)
Cp*GaǞB(C6F5)3 (5)
191.7
191.6
188.4
186.5
246.9
243.7
215.4
216.1
223.8–230.5
218.5–237.7
219.6–226.0
221.7–223.8
227.3
227.0
222.6
222.7
–
–
169.2
137.3
170.1
176.7
344.4
342.1
applicability was subsequently proven by a projected reac- Additionally Cp is in general a lot easier to obtain and a
tion of 1 with B(C6F5)3, which gave colorless crystals of much more cost-efficient ligand than Cp*. This is certainly
CpGaǞB(C6F5)3 (4) in 45% yield. The molecular structure relevant for technical applications where the carbene-like
of 4, determined by X-ray single-crystal structure analysis, character of 1 could be of use for various reactions, for
is shown in Figure 2.
example, with unsaturated compounds. Accordingly the
The Ga–B bond in 4 (215.4 pm) is identical within error presented convenient synthesis of GaCp might be the kiss
bars with the Ga–B bond in the corresponding GaCp* to awake this sleeping beauty in organometallic chemistry.
compound Cp*GaǞB(C6F5)3 (5) (see Table 1).[26] However,
the B–Ga–Cpcentroid angle in 4 is 170.1°, while it is consider-
ably larger in 5 (176.7°). Thus in contrast to the comparison
of 2 and 3, the higher steric demand of the Cp* group in 5
forces a less bent orientation.
Experimental Section
However, a closer inspection of the molecular structure
of 4 shows that additional short intramolecular Ga···F con-
tacts are present, where the shortest Ga–F distance (Ga1–
F102 290 pm) is well within the range of the sum of the
van der Waals radii (340 pm). This Ga···F interaction ad-
ditionally leads to a bending of the Cp ligand and to a large
variation in Ga–C bond lengths (220–226 pm).
Consequently, as in the case of 2, secondary contacts sig-
nificantly disturb the Ga–Cp interaction in 4 as well as the
Ga–Cp* interaction in 5, which makes a reasonable com-
parison of the central bonding parameters of the two com-
pounds (4 and 5) nearly impossible.[27] However, there
should be a difference between the donor abilities of GaCp
and GaCp*, as the sum of the C–B–C bond angles (Σ°CBC)
All manipulations were carried out under pure nitrogen by using
standard Schlenk techniques. NaCp was prepared according to the
literature.[31] B(C6F5)3 was purchased from Sigma–Aldrich. The
NMR spectra were recorded in [D6]benzene with a Bruker AV 300
spectrometer (1H 300.1 MHz, 11B 96.3 MHz, 13C 75.5 MHz, 19F
282.4 MHz, 71Ga 91.5 MHz). IR data were collected by using a
Bruker IFS 113v Spectrometer. The samples were measured with
the aid of an ATR unit. The Raman spectra were obtained with
a Dilor XY800 spectrometer (CCD camera, Wright instruments,
resolution 1.5 cm–1), measured in dodecane in a sealed glass tube.
EDX spectra were collected with an Ametek Genesis 4000 detector
connected to a scanning electron microscope Zeiss Supra VP40.
GaCp (1): NaCp (0.09 g, 1 mmol) and GaI (0.18 g, 0.9 mmol) were
suspended with cold toluene, benzene, pentane, or dodecane
in 4 is 344.4° and the arrangement of B(C6F5)3 is a bit (20 mL in each case), leading to a pure white residue and a colorless
solution. The cold solution was filtered and used right away with-
out further manipulation. 1H NMR (C6D6): δ = 5.8 (s, 5 H, Cp)
ppm. 13C NMR(C6D6): δ = 106.5 (s, Cp) ppm. 71Ga NMR (C6D6):
closer to a trigonal planar relative to that in 5, where the
sum of the C–B–C bond angles is 342.1°. As the sum of the
C–B–C bond angles in B(C6F5)3 is a good indicator for the
relative Lewis basicity of a bound donor – the more the
sum of angles differs from 360° the stronger is the do-
nor[28] – GaCp (1) is a slightly weaker donor compared to
GaCp*.[29] The marginally stronger donor abilities of
GaCp* do not come as a surprise, as a positive inductive
effect can be expected of the five methyl groups. Neverthe-
less the differences are small, and therefore GaCp can be
seen as a less sterically demanding analogue of GaCp*
opening up a wide range of further applications, for exam-
ple, in transition metal and rare earth chemistry.[30]
δ = –708.4 (br., GaCp) ppm. Raman (dodecane, 298 K): ν =
˜
262.1 cm–1.
CpGaǞGaCp2I (2): NaCp (0.2 g, 2.3 mmol) and GaI (0.41 g,
2.1 mmol) were suspended with cold toluene (30 mL), leading to a
pure white residue and a colorless solution. The cold solution was
filtered and layered with pentane (30 mL) at –30 °C. After a few
hours, the solution turned yellow, and a few yellow crystals of 2
were obtained.
CpGaǞB(C6F5)3 (4): A solution of GaCp (0.15 g, 1.1 mmol) in
cold toluene (–40 °C, 25 mL) was added to B(C6F5)3 (0.5 g,
1 mmol). The reaction mixture was warmed slowly to room tem-
perature under constant stirring overnight. The resulting bright yel-
low solution was filtered and concentrated in vacuo until the vol-
ume was ca. 10 mL. The toluene solution was then stored at –30 °C
to give colorless crystals of 4 (0.31 g, 0.45 mmol, 45% yield). 1H
NMR (C6D6): δ = 5.74 (s, 5 H, Cp) ppm. 11B NMR (C6D6): δ =
–3 (br., w1/2 = 2100 Hz) ppm. 13C NMR (C6D6): δ = 108.65 (s,
Cp), 137.39 (dm, J = 250 Hz, m-C6F5), 142.79 (m, p-C6F5), 148.06
(dm, J = 260 Hz, o-C6F5) ppm. 19F NMR (C6D6): δ = –128.9 (s,
Conclusions
We presented an easy synthesis – that can be carried out
with standard laboratory equipment – of GaCp (1), which
is a promising reagent in organometallic chemistry; for ex-
ample, it is less sterically demanding than the related Cp*
compound and might therefore open the possibility of
higher coordination numbers in coordination chemistry. m-C6F5), –142.1 (s, p-C6F5), –161.6 (s, o-C6F5) ppm. IR (ATR unit,
Eur. J. Inorg. Chem. 2011, 3681–3685
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3683

C. Schenk, R. Köppe, H. Schnöckel, A. Schnepf
SHORT COMMUNICATION
[9]
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298 K): ν = 443.6 (w), 472.5 (w), 559.3 (w), 615.3 (w), 655.8 (sh),
˜
661.5 (m), 692.4 (w), 731.0 (w), 771.5 (m), 825.5 (m), 960.5 (s),
979.8 (s), 1008.7 (w), 1087.8 (sh), 1103.3 (m), 1284.6 (w), 1375.2
(w), 1460 (m), 1516.0 (m), 1645.2 (w) cm–1.
[10]
Crystal Structure Data
[11]
[12]
[13]
[14]
CpGaǞGaCp2I (2): IGa2C15H15 Mr = 461.6 gmol–1, crystal dimen-
sions 0.4ϫ0.3ϫ0.3 mm3, orthorhombic, space group Pca21, a =
16.176(3) Å, b = 8.5188(17) Å, c = 11.319(2) Å, V = 1559.9(5) Å3,
Z = 4, ρcalcd = 1.966 g cm–3, μMo = 5.414 mm–1, 2θmax = 54.26°,
9155 measured, 1743 independent reflections (Rint = 0.0689); ab-
sorption correction: numerical (min./max. transmission 0.4143/
0.5381), R1 = 0.0313, wR2 = 0.0553; STOE IPDS II diffractometer
[Mo-Kα radiation (λ = 0.71073 Å), 150 K].
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The interaction of Ga and Cp in the multidecker sandwich
[-Ga(C5H5)Fe(C5H5)-]n[GaCl4]2n complex is rather weak and
the distance is very long relative to known GaCp* compounds:
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[15]
[16]
CpGaǞB(C6F5)3 (4): GaF15C23BH5 Mr = 646.8 gmol–1, crystal di-
mensions 0.3ϫ0.25ϫ0.2 mm3, monoclinic, space group C2/c, a =
18.288(4) Å, b = 12.382(3) Å, c = 20.547(4) Å, β = 108.96(3)°, V =
4400.3(15) Å3, Z = 8, ρcalcd = 1.953 gcm–3, μMo = 1.390 mm–1,
2θmax = 53.48°, 11093 measured, 4649 independent reflections (Rint
= 0.0770); absorption correction: numerical (min./max. trans-
mission 0.8244/0.9006), R1 = 0.0394, wR2 = 0.0974; STOE IPDS
II diffractometer [Mo-Kα radiation (λ = 0.71073 Å), 150 K]. The
structures were solved by direct methods and refined against F2 for
all observed reflections. Programs used: SHELXS and
SHELXL.[32]
[17]
[18]
[19]
[20]
The stretching vibration for GaCp (1) has been calculated to
be 262.3 cm–1 in the Raman spectra (C1 symmetry).
Quantum chemical calculations were carried out with the RI-
DFT module of the Turbomole program package by employing
the Becke–Perdew 86-functional. The basis sets were of SVP
quality. Turbomole: O. Treutler, R. Ahlrichs, J. Chem. Phys.
1995, 102, 346–354; BP-86-functional: A. D. Becke, Phys. Rev.
A 1988, 38, 3098–3100; J. P. Perdew, Phys. Rev. B 1986, 33,
8822–8824; RI-DFT: K. Eichkorn, O. Treutler, H. Öhm, M.
Häser, R. Ahlrichs, Chem. Phys. Lett. 1995, 240, 283–290; SVP:
A. Schäfer, H. Horn, R. Ahlrichs, J. Chem. Phys. 1992, 97,
2571–2577.
CCDC-822364 (for 2) and -822363 (for 4) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.as.uk/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
cle): EDX, IR and Raman spectra.
III
[21]
The presence of the Ga moiety (Cp2GaI) in 2 seems surpris-
Acknowledgments
ing at first glance. However, the formation of GaIII compounds
by applying “GaI” has been described before, for example, the
reaction of “GaI” with PPh3 gives Ph3PǞGaI3.[15] Probably,
two iodine atoms of a GaI3 intermediate were substituted by a
Cp ligand in a metathesis reaction, and the resulting GaCp2I
was trapped by GaCp to form crystals of 2. A further substitu-
tion of the third iodine would lead to the sterically crowded
GaCp3, which cannot easily get distorted to a tetrahedral ar-
rangement and can therefore hardly form donor–acceptor
bonds.
We are grateful to the Deutsche Forschungsgemeinschaft (DFG)
and the Fonds der Chemischen Industrie for financial support and
the Alexander von Humboldt Foundation for a Feodor Lynen fel-
lowship (C. S.). We also thank Jenny Luu for helpful discussions.
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Int. Ed. 2006, 45, 4447–4451.
[23]
[24]
[25]
P. Jutzi, B. Neumann, G. Reumann, L. O. Schebaum, H.
Stammler, Organometallics 2001, 20, 2854–2858.
An EDX spectrum (EDX spectra are available in the Support-
ing Information) of the gray residue reveals an average gallium/
carbon ratio of 1:3.4, while the gallium/carbon ratio in 2 is
1:7.5 and the gallium/carbon ratio in GaCp3 is 1:15. Conse-
quently, the gray residue and GaCp3 are potential dispropor-
tionation products of 2.
[26]
[27]
N. J. Hardman, P. P. Power, J. D. Gordon, C. L. B. Macdonald,
A. H. Cowley, Chem. Commun. 2001, 1866–1867.
The sensitivity of the Ga–C bonding also becomes obvious in
the case of Cp*GaǞB(C6F5)3 (5), where a second solid-state
structure with a different packing of 5 is known, leading to a
B–Ga–Cpcentroid angle of 179.1° and Ga–C distances between
221 and 224 pm.[24]
.
[28]
M. C. Kuchta, J. B. Bonanno, G. Parkin, J. Am. Chem. Soc.
1996, 118, 10914–10915.
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Eur. J. Inorg. Chem. 2011, 3681–3685

A Convenient Synthesis of Cyclopentadienylgallium
[29] This finding is in accordance with DFT calculations, where the
bond enthalpy between GaCp and B(C6F5)3 is calculated to be
–9.4 kJ/mol in 4, while it is –30.1 kJ/mol for 5 between GaCp*
and B(C6F5)3. Additionally, further calculations applying the
less sterically demanding acceptor GaMe3 also shows a small
difference in donor strength between GaCp and GaCp*, as the
reaction enthalpies for the formation of the donor–acceptor
complex are nearly identical; that is, –15.3 kJ/mol for Cp and
–20.6 kJ/mol for Cp*.
[30]
[31]
P. W. Roesky, Dalton Trans. 2009, 1887–1893.
T. K. Panda, M. T. Gamer, P. W. Roesky, Organometallics 2003,
22, 877–878.
[32] G. M. Sheldrick, Acta Crystallogr. 2008, A64, 112–122.
Received: May 24, 2011
Revised: July 1, 2011
Published Online: August 1, 2011
Eur. J. Inorg. Chem. 2011, 3681–3685
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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