Expanding the Size of Catecholesters - Modified Ligands for the Hierarchical Assembly of Dinuclear Titanium(IV) Helicates

Article abstract of DOI:10.1002/zaac.201500543

Five 2,3-dihydroxybenzoic acid derivatives 1 - 5 were used as starting materials to obtain the corresponding methyl and ethyl esters. Those were applied as ligands in the hierarchical self-assembly of lithium-bridged dinuclear titanium(IV) complexes 1a-4a

Full text of DOI:10.1002/zaac.201500543

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
DOI: 10.1002/zaac.201500543
Expanding the Size of Catecholesters – Modified Ligands for the
Hierarchical Assembly of Dinuclear Titanium(IV) Helicates
[a]
[a]
[a]
[b]
David Van Craen, Marita de Groot, Markus Albrecht,* Fanfang Pan, and
Kari Rissanen[
b]
Dedicated to Professor F. Ekkehardt Hahn on the Occasion of His 60th Birthday
Keywords: Hierarchical self-assembly; Titanium; 2,3-Dihydroxybenzoic esters; NMR spectroscopy
Abstract. Five 2,3-dihydroxybenzoic acid derivatives 1 – 5 were used and 5b. The equilibria between the mononuclear triscatecholate com-
as starting materials to obtain the corresponding methyl and ethyl es-
ters. Those were applied as ligands in the hierarchical self-assembly by H NMR spectroscopy in [D
plexes (monomer) and the dinuclear helicates (dimer) were observed
1
6
4
]DMSO and [D ]MeOH at room tem-
of lithium-bridged dinuclear titanium(IV) complexes 1a–4a, 1b–3b,
perature.
Introduction
A strong motivation in supramolecular chemistry is the imi-
tation of natural systems or principles. According to the helical
[1]
structure of e.g. double-stranded DNA Lehn defined the term
helicate”[ for a metallo-supramolecular entity consisting of
2]
“
linear oligodentate ligands twisting around two or more central
metal atoms. Hierarchically assembled helicates[3–6] differ
from classical helicates in a way that non-covalent linkers are
within the ligands. This enables hierarchical self-assembly of Figure 1. Force field (Spartan essential 08) generated model of the
helicates in two successive metal coordination steps.[ The dinuclear titanium(IV) complex without substitution at the catechol
3]
[4]
methyl ester (a) and with phenyl groups in 5-position of the ligand
linkage, which leads to such helicates may exist of one,
(
b). The deeper groove in case of the substituted derivative is well
two,[ or three
5]
[3,6]
metal atoms.
recognized.
Since one decade we focus on catechols bearing aldehyde,
keto or ester substituents[3,7,8] in 3-position of the aromatic
unit. They can be used for the formation of hierarchically as-
sembled lithium-bridged dinuclear titanium(IV) helicates (Fig-
ure 1). Two consecutive assembly steps (Scheme 1) are neces-
sary for this: The formation of a triscatecholate complex
(
monomer) and the dimerization of two monomers via the co-
[3]
ordination of lithium cations .
In solution, both dimer and monomer are observed while
[8b,8c]
in the solid state usually only the dimer is found.
The
equilibrium in solution is described by the dimerization con-
stant Kdim, which depends heavily on the solvent used. Sol-
Scheme 1. Schematic representation of the hierarchical assembly of a
triple lithium bridged dinuclear helicate. The dimeric species is usually
obtained as a racemate of the right-handed and the left-handed form.
*
Prof. Dr. M. Albrecht
Fax: +49-241-809-2385
[
8]
E-Mail: Markus.Albrecht@oc.rwth-aachen.de
The helicity can be controlled by introducing chiral esters.
[
[
a] Institut für Organische Chemie
RWTH Aachen
vents like DMSO, which coordinate lithium cations well, de-
Landoltweg 1
[3,7a]
52074 Aachen, Germany
stabilize the dimer and result in a low Kdim
.
On the other
b] Department of Chemistry
University of Jyväskylä
P.O. Box 35
hand, solvents like methanol or THF with a poor ability to
coordinate lithium cations stabilize the dimer and increase the
dimerization constant.[
3,7a]
40014 University Jyväskylä, Finland
Z. Anorg. Allg. Chem. 2015, 641, (12-13), 2222–2227
2222
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
The dimeric complexes have the shape of a twisted cylinder
with cavities/grooves formed by the aromatic platforms of the
[9]
ligands. With host-guest chemistry and the possibility to per-
form chemical reactions or even catalysis in the vicinity of the
compounds in mind our focus was to pronounce the helical
character of the dimeric species. Theoretically a deeper helical
groove is achieved by expanding the aromatic units introduc-
ing peripheral substituents. Thus we synthesized catecholes-
ters, which bear appropriate substituents at the ligand-back.
Herein we show the behavior of substituted methyl or ethyl
esters of 2,3-dihydroxybenzoic acid in the formation of hierar-
chically assembled helicates.
Results and Discussion
As starting material required derivatives of 2,3-dihydroxy-
benzoic acid were synthesized according to the literature: 5-
[
10]
bromo-2,3-dihydroxybenzoic acid (1),
4,5-dibromo-2,3-di-
[11]
hydroxybenzoic acid (2),
and 5-nitro-2,3-dihydroxybenzoic
acid (3).[ The regioselectivity of 2 was determined by NOE
NMR spectroscopy. 2,3,4-Trihydroxybenzoic acid (4) is com-
mercially available. 5-Phenyl-2,3-dihydroxy-benzoic acid (5)
was obtained in a Suzuki reaction of 1 with phenylboronic acid
12]
(Scheme 2) in 29% yield.
Scheme 3. Synthesis of ligands and titanium(IV) complexes.
Scheme 2. Synthesis of the phenyl catechol 5 via Suzuki coupling of
compound 1 with PhB(OH)
2
.
The acids were esterified with methanol or ethanol catalyzed
by sulfuric acid to obtain the corresponding ligands
[13]
[12b]
and 4a-H2[14] as
(
Scheme 3) 1a-H2 , 2a-H , 3a-H ,
2
2
methyl esters as well as 1b-H , 2b-H , 3b-H , 5b-H as ethyl
2
2
2
2
esters.
Complexes are formed in methanol overnight in the pres-
ence of Li CO (2 equiv.) as lithium source as well as base
2
3
4 6 2
Figure 2. Structure of Li [(4a) Ti ] as found in the crystal. Hydrogen:
using two equiv. of TiO(acac)2 and six equiv. of ligand white; carbon: grey; oxygen: red; lithium: blue; titanium: yellow; left:
(
Scheme 3). The complexes 1a – 4a, 1b – 3b, and 5b were view along the titanium–titanium axis; right: view orthogonal to the
obtained in quantitative yields after solvent removal. Red crys-
titanium–titanium axis and into the helical groove.
tals of complex Li [(4a) Ti ] were obtained by crystallization
4
6
2
from methanol/diethyl ether. The crystal structure (Figure 2)
proves the dimeric form. With a Ti–Ti distance (5.493 Å) and merization constant Kdim was determined by H NMR spec-
The equilibrium between dimer and monomer with the di-
1
an average Li–O distance (1.928 Å) the crystal data correspond troscopy. Monomer and dimer can be distinguished by their
[3]
well with already published structures. However, the uncoor- chemical shift δ. The aliphatic signals of the dimeric ester due
dinated phenolic hydroxides located at the termini of the helic- to anisotropic effects of neighboring aromatic units show a
ate are well recognized. The selectivity of metal coordination high-field shift in contrast to the monomer.[ For example, the
to the hydroxides in 2- and 3-position of the ligand seems to be high-field shift between monomer and dimer in case of the
3]
[
3]
surprising but it most probably is driven by the thermodynamic 2,3-dihydroxymethylbenzoate ligand is Δδ = 0.69 ppm.
stability of the triple-lithium bridged complex. In the future Furthermore, for the first methylene unit of long-chain ester
the hydroxides in 4-position will be used for further derivati- resonances of diastereotopic protons are observed only in case
zation or metal coordination.
of the dimer due to a hindered inversion of the helical arrange-
Z. Anorg. Allg. Chem. 2015, 2222–2227
2223
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
ment of the complex.[3,15] This behavior is shown in Figure 3 stituent which weakens the coordination of the bridging lith-
for the ethyl complex Li [(2b) Ti ] as a representative exam- ium cations.
4
6
2
ple.
The same trend to lower dimerization constants due to elec-
tron withdrawing substituents is observed for the ethyl esters.
The dimerization constants for the complex Li [(1b) Ti ] with
4
6
2
one bromine substituent at each ligand are K ([D ]MeOH) =
dim
4
4000 m–1 and Kdim([D ]DMSO) = 6 m (Table 1, entry 5).
–1
2
6
With two bromine substituents (Li [(2b) Ti ], Table 1, entry
4
6
2
–1
6
) the constants are K ([D ]MeOH) = 800 m
Kdim([D ]DMSO) = 5 M . The expected decrease of more
and
dim
4
–1
6
than an order of magnitude of the values in [D ]MeOH is ob-
4
served.
The nitro-substituted ethyl ester complex Li [(3b) Ti ]
4
6
2
(Table 1, entry 7) behaves similar to the corresponding methyl
ester complex Li [(3a) Ti ] (Table 1, entry 3). Only the mono-
4
6
2
meric species is observed in [D ]DMSO. The dimer is found
6
–1
as a minor component in [D ]MeOH (K
= 110 m ) due to
dim
4
the more electron donating ethyl ester in contrast to the methyl
[(2b) Ti ] showing both ester.
4 6 2
1
Figure 3. H NMR spectrum of complex Li
the high-field shift of the aliphatic signals and the diastereotopic be-
havior of the CH signals of the dimer. M = monomer and D = dimer.
Finally, the complex Li [(5b) Ti ] with a phenyl substituent
4
6
2
2
at the aromatic system of the ligand was investigated (Table 1,
entry 8). A high dimerization constant is expected due to the
introduction of the electron donating phenyl group. This as-
sumption is confirmed by the dimerization constants both in
For the new complexes of peripheral substituted esters the
following dimerization features are observed: The dimeric
form Li [(1a) Ti ] of the triscatecholate complex Li [(1a) Ti]
4
6
2
2
3
[
D ]MeOH and in [D ]DMSO. The constant in [D ]MeOH
4 6 4
with one electron withdrawing bromine group at each ligand
–1
(Kdim = 163000 m ) is seven times higher than the highest of
(
8
Table 1, entry 1) is highly favored in [D ]MeOH (K
=
dim
= 3 m mainly
dim
4
–1
–
1
–1
the ethyl esters (Li [(1b) Ti ]: Kdim = 24000 m ) and twice
4 6 2
5000 m ), whereas in [D ]DMSO with K
6
as high as found for the methyl esters (Li [(1a) Ti ]: K =
dim
4
6
2
the monomer is present. Analogously the major product of
complex Li [(2a) Ti ] with an additional bromine group is the
dimer in [D ]MeOH and the monomer in [D ]DMSO (Table 1,
–
1
8
5000 m ). A similar trend is observed for [D ]DMSO with
6
4
6
2
–1
the highest Kdim = 370 M .
4
6
entry 2). Interestingly, the dimerization constant of this deriva-
tive is nearly one order of magnitude lower in [D ]MeOH with
4
Conclusions
–
1
Kdim = 11500 m in comparison to Li [(1a) Ti ]. A dimeriza-
4
6
2
tion constant within the same order of magnitude is observed
Herein we describe the synthesis of eight novel catechol es-
for complex Li [(4a) Ti ] (Table 1, entry 4) with one aromatic ter complexes. The influence of electron withdrawing and elec-
4
6
2
–1
hydroxyl group in [D ]MeOH (Kdim = 3600 m ). In tron donating substituents on the aromatic system of 2,3-dihy-
4
[
D ]DMSO no K can be determined because more than two droxybenzoic esters during the dimerization process of trisca-
6
dim
species are present. This observation necessitates further in- techolate titanium(IV) complexes is shown. The dimer be-
vestigations with a focus on a possible coordination of the third comes more destabilized by introducing more or stronger elec-
hydroxyl group resulting in more complicated aggregates.
tron withdrawing groups due to the lack of electron density at
the carbonyl function, which is needed to establish a stable
lithium bridge between two monomers. On the other hand, as
expected, an electron donating group stabilizes the dimer.
With the presented examples we are able to modify the over-
all shape of the obtained complexes and to introduce deeper
grooves within the coordinated ligand in order to use the com-
plexes for host-guest chemistry.
Table 1. Dimerization constants for the helicates Li
]MeOH and [D ]DMSO.
4
6 2
[(L) Ti ] in
[D
4
6
Entry
L
R
Kdim([D
4
]MeOH)a)
Kdim([D
6
]DMSO)a)
1
2
3
4
5
6
7
8
1a
2a
3a
4a
1b
2b
3b
5b
Me
Me
Me
Me
Et
Et
Et
Et
85000 M–1
11500 M–1
only monomer
3600 M–1
3 M–1
12 M
–1
only monomer
–
–1
–1
24000 M
6 M
–1
–1
800 M
110 M–1
163000 M–1
5 M
only monomer
370 M
Experimental Section
–1
Materials: 2,3-Dihydroxybenzoic acid and 2-hydroxy-3-methoxy-
benzoic acid were obtained from Alfa Aesar. 2,3,4-Trihydroxybenzoic
acid was purchased from Sigma Aldrich. All purchased chemicals were
1
a) Determined by H NMR spectroscopy.
The lowest dimerization constant is obtained by introduction
of a nitro group (Li [(3a) Ti ]). Only the monomer is observed
4
used without further purification. [D ]Methanol was acquired from
4
6
2
Euriso-top and [D ]DMSO was preserved from Cambridge Isotope
6
in [D ]DMSO as well as in [D ]MeOH (Table 1, entry 3). This Laboratories. Solvents used during the synthesis or the workup were
6
4
is due to the strong electron withdrawing character of the sub- purified by distillation.
Z. Anorg. Allg. Chem. 2015, 2222–2227
2224
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
General Methods: NMR spectroscopy was carried out with a Mercury (Carom), 123.05 (Carom), 118.35 (Carom), 113.83 (Carom), 113.10 (Carom).
300, a Varian VNMRS 400 or a Varian VNMRS 600 device. Mass
IR (KBr): ν˜ = 3451 (s), 3094 (m), 2961 (m), 2584 (w), 2289 (w), 2070
spectrometry was performed with a Finnigan SSQ 7000 (EI) and a
LTQ Orbitrap XL (ESI) device. IR spectra were measured with a Per-
kin-Elmer Spektrum 100 and elementary analysis was carried out with
a Vario EL Element Analyzer. Melting points were measured with a
BÜCHI Melting-Point B-540 device and represent the temperature
range between the start and the finished melting process.
(w), 1989 (w), 1662 (vs), 1449 (vs), 1303 (vs), 1216 (vs), 1150 (vs),
–
1
1005 (m), 863 (s), 788 (vs), 678 (m) cm . MS (EI, 70 eV): m/z =
+
+
2
311.9 (M , 9%), 293.9 [M – H O, 20%).
5-Phenyl-2,3-dihydroxybenzoic Acid (5): Sodium carbonate
(
535 mg, 5.05 mmol, 5 equiv.) was dissolved in water (8 mL). After-
wards 5-bromo-2,3-dihydroxybenzoic acid (1) (233 mg, 1.01 mmol,
1 equiv), phenylboronic acid (134 mg, 1.1 mmol, 1.1 equiv), and palla-
dium(II) chloride (7 mg, 0.04 mmol, 0.04 equiv.) were added to the
General Procedure for the Preparation of the Esters: The corre-
sponding derivatives of 2,3-dihydroxybenzoic acid were refluxed in
methanol or ethanol with one equivalent sulfuric acid overnight. The stirred mixture in a nitrogen atmosphere. The reaction was stirred at
mixtures were poured into water and the solution was extracted with
room temperature overnight. 5-Phenyl-2,3-dihydroxybenzoic acid (5)
ethyl acetate once. Afterwards the organic layer was washed with satu- was obtained after filtration of the reaction mixture and acidifying the
rated aqueous sodium carbonate solution and dried with magnesium filtrate. Yield: 29% (67 mg, 0.29 mmol, colorless hygroscopic solid).
–
1
sulfate. The desired methyl and ethyl esters were obtained in satisfac-
tory purity after removing the solvent under reduced pressure.
M.p.: 222–224 °C. C13
4.55%; found:
]DMSO, 25 °C): δ = 9.51 (s, 1 H, OH), 7.54–7.51 (m, 2 H, Harom),
H
C
10
O
66.09,
4
(230.2 g·mol )·1/3H
2
O: calcd. C 66.10,
H
H
4.301%. 1H NMR (600 MHz,
[
D
6
[
10]
and 3[12] as well as
Compounds from the Literature: Acids 1
4
3
7
.49 [d, J(H,H) = 2.3 Hz, 1 H, Harom.], 7.40 (t, JH,H = 7.7 Hz, 2 H,
arom), 7.32–7.27 (m, 2 H, Harom), two missing OH signals are not
]DMSO, 25 °C): δ = 172.76
H), 150.47 (Carom), 146.84 (Carom), 139.87 (Carom), 131.26
arom), 129.37 (Carom), 127.41 (Carom), 126.55 (Carom), 119.30 (Carom),
18.21 (Carom), 113.91 (Carom). IR (KBr): ν˜ = 3499 (m), 3059 (m),
[13]
[12b]
[14]
ligands 1a-H
2
,
3a-H
2
,
and 4a-H
2
are already well described
H
in the literature.
13
observed. C NMR (151 MHz, [D
6
(CO
2
4 6 2
Crystallographic Details: Red needles of complex Li [(4a) Ti ] were
(
C
crystallized from methanol/diethyl ether. The data were collected at
1
2
1
1
20.01(10) K with an Agilent Super-Nova diffractometer using mirror-
317 (w), 2089 (w), 1904 (w), 1676 (s), 1470 (s), 1304 (s), 1223 (vs),
[
16]
monochromatized Cu-K
α
(λ = 1.54184Å) radiation. CrysAlisPro
–1
153 (s), 1069 (m), 967 (w), 879 (m), 767 (s), 697 (s) cm . MS (EI,
was used for both data collection and processing. The intensities were
corrected for absorption using the analytical face index absorption cor-
+
+
7
2
0 eV): m/z = 230.0 (M , 57%), 212.0 [M – H O, 100%).
[
17]
rection method.
The structure was solved by direct method with 4,5-Dibromo-2,3-dihydroxymethylbenzoate (2a-H ): Yield: 54%,
2
[18]
SHELXS
and refined by full-matrix least-squares methods using
8 6 2 4
88 mg, 0.27 mmol, pale red solid. M.p.: 144–147 °C. C H Br O
–1
the OLEX2,[ which utilizes the SHELXL-2013 module.[18] All non- (325.9 g·mol ): calcd. C 29.48, H 1.86%; found: C 29.96, H 2.23%.
19]
1
hydrogen atoms were refined with anisotropic thermal parameters. All
6
H NMR (600 MHz, [D ]DMSO, 25 °C): δ = 10.61 (s, 1 H, OH),
the other hydrogen atoms were introduced in proper positions with 10.37 (s, 1 H, OH), 7.51 (s, 1 H, Harom), 3.88 (s, 3 H, CH3). C NMR
isotropic thermal parameters using the “riding model” except the (151 MHz, [D ]DMSO, 25 °C): δ = 168.39 (CO CH ), 148.60 (Carom),
1
3
6
2
3
hydrogen atoms for O23 and O32, for which the hydrogen atoms were
146.29 (Carom), 122.77 (Carom), 118.58 (Carom), 113.97 (Carom), 113.60
located from difference Fourier maps. The positions of these hydrogen (Carom), 53.33 (OCH ). IR (KBr): ν˜ = 3618 (w), 3447 (m), 3081 (w),
3
atoms were restrained by “DFIX” and their isotropic thermal param-
eters were refined freely. Two of the three diethyl ether molecules were (vs), 1218 (vs), 1133 (vs), 1017 (m), 898 (m), 790 (s), 678 (s) cm .
disordered. Their ADPs were restrained with command “ISOR”. In MS (EI, 70 eV): m/z = 325.8 (M , 60%), 293.8 (M -CH O, 100%).
2958 (w), 2299 (w), 2083 (w), 1922 (w), 1661 (s), 1432 (vs), 1290
–
1
+
+
4
one of the diethyl ether molecules, one ethyl group was split over two
5
-Bromo-2,3-dihydroxyethylbenzoate (1b-H
2
). Yield: 69%,
BrO
positions. For another diethyl ether molecule, the occupancy is 0.75
with another 25% probability occupied by MeOH. Geometry of the
three diethyl ether molecules was restrained as well if necessary. The
water molecule coordinated to Li4 was also disordered. Its ADP was
restrained with “ISOR” without splitting.
90 mg, 0.35 mmol, pale red solid. M. p.: 81–84 °C. C
9
H
9
4
–
1
(
1
261.1 g·mol ): calcd. C 41.41, H 3.47%; found: C 41.42, H 3.558%.
H NMR (600 MHz, [D ]DMSO, 25 °C): δ = 7.28 (d, JH,H = 2.4 Hz,
6
4
4
H,H
J J =
H,H = 2.4 Hz, 1 H, Harom), 4.32 (q, 3
1
7
H, Harom), 7.12 (d,
3 3
.1 Hz, 2 H, OCH CH ), 1.30 (t, JH,H = 7.1 Hz, 3 H, CH ), the OH
3
2
1
3
Crystallographic data (excluding structure factors) for the structure in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
signals were not observed. C NMR (151 MHz, [D ]DMSO, 25 °C):
δ = 168.44 (CO CH ), 149.43 (Carom), 148.20 (Carom), 122.90 (Carom),
121.59 (Carom), 115.24 (Carom), 109.79 (Carom), 62.13 (OCH CH ),
14.34 (CH ). IR (KBr): ν˜ = 3422 (s), 3192 (m), 2979 (w), 2724 (w),
6
2
2
2
3
3
number CCDC-1407855 for Li
E-Mail: deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
4
[(4a)
6
Ti
2
] (Fax: +44-1223-336-033;
2328 (w), 2083 (w), 1884 (w), 1661 (vs), 1449 (vs), 1282 (vs), 1135
–
1
(vs), 1015 (s), 862 (s), 787 (s), 700 (w) cm . MS (EI, 70 eV): m/z =
+
+
+
2
(
2 6
62.0 (M , 38%), 260.0 (M , 35%), 216.0 (M -C H O, 90%), 213.9
4
,5-Dibromo-2,3-dihydroxybenzoic Acid (2):[11] 2,3-Dihydroxyben-
zoic acid (1 g, 6.5 mmol, 1 equiv.) was dissolved in acetic acid
20 mL). Bromine (5.2 g, 32.5 mmol, 5 equiv.) was added dropwise to 4,5-Dibromo-2,3-dihydroxyethylbenzoate (2b-H
this solution and the mixture was stirred overnight. The precipitated 66 mg, 0.19 mmol, pale red solid. M.p.: 135–136 °C. C
+
2 6
M -C H O, 100%).
(
2
): Yield: 39%,
Br
(340.0 g·mol ): calcd. C 31.80, H 2.37%; found: C 32.19, H 2.811%.
9
H
8
2 4
O
–
1
solid was filtered and washed with acetic acid to obtain 4,5-dibromo-
1
2
,3-dihydroxybenzoic acid (2). Yield: 59% (1.2 g, 3.85 mmol, color-
H NMR (600 MHz, [D
6
]DMSO, 25 °C): δ = 7.50 (s, 1 H, Harom),
CH ), 1.37–1.24 (m, 3 H, CH ), the OH sig-
nals were not observed. C NMR (151 MHz, [D ]DMSO, 25 °C): δ
= 168.16 (CO CH ), 148.96 (Carom), 146.42 (Carom), 122.48 (Carom),
.52 (s, 1 H, Harom), 6.72–3.45 (br., 1 H, OH). 13C NMR (151 MHz, 118.44 (Carom), 113.80 (Carom), 113.43 (Carom), 62.37 (OCH
CH ),
]DMSO, 25 °C): δ = 171.30 (CO H), 149.90 (Carom), 145.96 14.33 (CH
). IR (KBr): ν˜ = 3437 (m), 2968 (m), 2463 (w), 2304 (w),
–1
less solid). M.p.: 241–243 °C. C
2
7
H
4
Br
2
O
4
(311.9 g·mol ): calcd. C
4.40–4.28 (m, 2 H, OCH
2
13
3
3
1
6.95, H 1.29%; found: C 26.85, H 1.331%. H NMR (600 MHz,
6
[D
6
]DMSO, 25 °C): δ = 13.6–10.8 (br., 1 H, OH), 10.33 (s, 1 H, OH),
2
2
7
2
3
[D
6
2
3
Z. Anorg. Allg. Chem. 2015, 2222–2227
2225
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
1
2
7
C
084 (w), 1660 (vs), 1430 (s), 1291 (s), 1218 (s), 1102 (s), 1020 (vs),
3.13, N 4.04%. H NMR (400 MHz, [D
4
]MeOH, 25 °C): monomer δ
–1
+
+
97 (vs) cm . MS (EI, 70 eV): m/z = 340.0 (M , 9%), 293.9 (M -
O, 27%).
= 8.19–8.10 (m, 1 H, Harom), 7.26–7.16 (m, 1 H, Harom), 3.89–3.80 (m,
1
2
H
6
3 H, CH
3
); no dimer was observed. H NMR (300 MHz, [D
6
]DMSO,
H,H = 2.8 Hz, 1 H, Harom), 6.94 (d,
H,H = 2.8 Hz, 1 H, Harom), 3.71 (s, 3 H, CH ); no dimer was observed.
MS (ESI-FTMS, neg.): m/z calcd. for C24
4
2
5 °C): monomer δ = 7.95 (d,
J
5-Nitro-2,3-dihydroxyethylbenzoate (3b-H
0,88 mmol, red solid). M. p.: 120–122 °C. C
2/3H
2
): Yield: 59%, 0,20 g,
4
J
3
–
1
H
9
NO
6
(227.17 g·mol )·
–
9
15 3
H N O18LiTi (monomer):
O: calcd. C 45.19, H 4.35, N 5.86%; found: C 44.93, H 3.973,
+
2
6
M
87.99956 (M -Li ); found: 688.03668.
1
3
N 5.21%. H NMR (600 MHz, CDCl , 25 °C): δ = 11.76 (s, 1 H, OH),
8
.35 (d, 4
J
H,H = 2.7 Hz, 1 H, Harom), 7.94 (d, 4
J
H,H = 2.7 Hz, 1 H, Li
4 6 2 36 4 2
[(4a) Ti ]: Yield: quantitative. C48H O30Li Ti
(1216.3 g·mol–1)·
CH ), 3MeOH: calcd. C 46.67, H 3.69%; found: C 46.89, H 3.764%.
3
H
arom), 5.98 (s, 1 H, OH), 4.49 (q, JH,H = 7.2 Hz, 2 H, OCH
2
3
.46 (t, 4
5 °C): δ = 169.25 (CO
arom.) 117.20 (Carom), 114.17 (Carom), 111.82 (Carom), 62.88
OCH CH ), 14.10 (CH ). IR (KBr): ν˜ = 3493 (s), 3405 (m), 3101
m), 2993 (w), 2945 (w), 2756 (w), 2325 (w), 2246 (w), 2164 (w), (s, 3 H, CH
J
H,H = 7.2 Hz, 3 H, CH
). 13C NMR (151 MHz, CDCl
,
1
1
2
3
3
4
H NMR (300 MHz, [D ]MeOH, 25 °C): dimer (major compound): δ
= 7.04 (d, JH,H = 8.9 Hz, 1 H, Harom), 6.20 (d, JH,H = 8.9 Hz, 1 H,
arom), 3.13 (s, 3 H, CH
JH,H = 8.8 Hz, 1 H, Harom), 6.25 (d, JH,H = 8.8 Hz, 1 H, Harom), 3.78
). MS (ESI-FTMS, neg.): m/z calcd. for C48
(dimer): 1209.07360 (M
3
3
2
CH ), 154.09 (Carom), 145.48 (Carom), 140.01
2
(
(
(
C
H
3
3
); monomer (minor compound): δ = 7.15 (d,
3
2
3
3
–
3
H
36
O30Li
3
Ti
2
+
2084 (w), 2025 (w), 1996 (w), 1889 (w), 1820 (w), 1779 (w), 1665
D
-Li ); found: 1209.13269; m/z calcd. for
–
+
(vs), 1603 (m), 1525 (s), 1466 (vs), 1412 (m), 1381 (w), 1337 (vs),
C
24
H
18
O
15LiTi (monomer): 601.02907 (M
M
-Li ); found: 601.05969.
1
8
=
295 (vs), 1225 (vs), 1156 (vs), 1081 (s), 1020 (s), 944 (w), 908 (m),
–1
Crystal
Data
for
Li [(4a) Ti ]:
36
C61.25H74.25Li O Ti ,
63 (m), 820 (w), 793 (s), 741 (s), 709 (s) cm . MS (EI, 70 eV): m/z
4
6
2
4
2
+
+
0.038ϫ0.064ϫ0.136 mm, M = 1510.01, triclinic, space group P2 /c,
a = 12.2332(5) Å, b = 39.9247(18) Å, c = 15.2583(8) , α = 90°, β =
226.8 (M , 100%), 180.8 (M –C
2
H
6
O, 84%).
1
3
–3
5-Phenyl-2,3-dihydroxyethylbenzoate (5b-H
2
): Yield: 30%, 40 mg, 108.824(8)°, γ = 90°, V = 7053.7(6) , Z = 4, ρ = 1.422 g·cm , μ =
–
1
0.15 mmol, colorless hygroscopic solid. M.p.: 152–154 °C. C15
H
14
O
4
2.740 mm , F(000) = 3143, 23522 reflections (θmax = 66.75°) mea-
sured (12396 unique, Rint = 0.0609, completeness = 99.0%), Final R
–1
(
258.3 g·mol )·1/3H
2
O: calcd. C 68.17, H 5.59%; found: C 68.47, H
.624%. H NMR (400 MHz, CDCl , 25 °C): δ = 11.01 (s, 1 H, OH),
.61 (d, JH,H = 2.2 Hz, 1 H, Harom), 7.55–7.51 (m, 2 H, Harom), 7.45–
1
5
7
7
3
indices [I Ͼ 2σ(I)]: R
= 0.1256, wR = 0.2659. GOF = 1.088 for 1003 parameters and 95
.39 (m, 2 H, Harom), 7.37 (d, JH,H = 2.2 Hz, 1 H, Harom), 7.35–7.29 restraints, largest diff. peak and hole 1.351/–0.519 e· .
H,H = 7.1 Hz, 2 H,
). 13C NMR (101 MHz,
), 148.34 (Carom), 145.22 (Carom),
40.02 (Carom), 132.63 (Carom), 128.76 (Carom), 127.13 (Carom), 126.72
arom), 118.87 (Carom), 118.55 (Carom), 112.70 (Carom), 61.77
OCH CH ), 14.19 (CH ). IR (KBr): ν˜ = 3472 (s), 3052 (m), 2300
w), 2097 (w), 1890 (w), 1656 (vs), 1462 (s), 1306 (vs), 1171 (vs),
1 2
= 0.0967, wR = 0.2450, R indices (all data):
4
R
1
2
4
–3
(
m, 1 H, Harom), 5.80 (s, 1 H, OH), 4.43 (q, 3
J
–
1
), 1.43 (t, 3JH,H = 7.1 Hz, 3 H, CH
CH
4 6 2 54 42 6 24 4 2
Li [(1b) Ti ]: Yield: quantitative. C H Br O Li Ti (1677.8 g·mol )·
OCH
CDCl
1
(
(
(
2
CH
, 25 °C): δ = 170.33 (CO
3
3
1
2H
2
O: calcd. C 37.84, H 2.71%; found: C 37.93, H 3.025%. H NMR
3
2
2
(
4
400 MHz, [D ]MeOH, 25 °C): dimer (major compound): δ = 7.21 (d,
4
4
JH,H = 2.4 Hz, 1 H, Harom), 6.66 (d, JH,H = 2.4 Hz, 1 H, Harom), 3.76–
C
3
3.66 (m, 1 H, CH
2
2
CH
group overlaps with the solvent signal; monomer
), 6.82–6.79 (m, 1 H,
3 3
), 1.13 (t, JH,H = 7.1 Hz, 3 H, CH ), the other
2
3
3
proton of the CH
(minor compound): δ = 7.04–7.00 (m, 1 H, H
arom
Harom), 4.40 (q, J
–1
1025 (s), 873 (m), 767 (s), 689 (m) cm . MS (EI, 70 eV): m/z = 258.2
3
3
+
+
= 7.1 Hz, 2 H, CH CH ), 1.39 (t, J
H,H
= 7.1 Hz,
(M , 31%), 212.1 (M –C
2
H
6
O, 100%).
H,H
2
3
1
3
3 6
H, CH ). H NMR (300 MHz, [D ]DMSO, 25 °C): monomer (major
–
1
4
4
Li
4
[(1a)
O·2MeOH: calcd. C 35.46, H 2.50%; found: C 35.49, H 2.702%.
H NMR (400 MHz, [D ]MeOH, 25 °C): dimer (major compound): δ
6 2 6 4 2
Ti ]: Yield: quantitative. C48H30Br O24Li Ti (1593.7 g·mol )· compound): δ = 6.88 (d, JH,H = 2.5 Hz, 1 H, Harom), 6.25 (d, JH,H =
2H
2
2.5 Hz, 1 H, Harom), 4.13 (q, 3JH,H = 7.1 Hz, 2 H, CH
2
CH
3
), 1.22 (t,
1
3
4
3
JH,H = 7.1 Hz, 3 H, CH ); dimer (minor compound): δ = 6.75–6.71
4
4
3
=
7.22 (d, JH,H = 2.4 Hz, 1 H, Harom), 6.67 (d, JH,H = 2.4 Hz, 1 H, (m, 1 H, Harom), 6.55–6.51 (m, 1 H, Harom), 1.31 (t, JH,H = 7.1 Hz,
arom), 3.21 (s, 3 H, CH ); monomer (minor compound): δ = 7.17 (d, 3 H, CH ), the two signals of the CH group vanish in the baseline.
H,H = 2.2 Hz, 1 H, Harom), 7.05 (d, JH,H = 2.2 Hz, 1 H, Harom), 3.92 MS (ESI-FTMS, pos.): m/z calcd. for C54
H
3
3
2
4
4
+
J
H
42Br
6
O24Li
5
Ti
2
(dimer):
1
+
(
(
3 6 D
s, 3 H, CH ). H NMR (400 MHz, [D ]DMSO, 25 °C): monomer 1684.68585 (M +Li ); found: 1684.68896.
4
major compound): δ = 6.86 (d, JH,H = 2.5 Hz, 1 H, Harom), 6.22 (d,
4
Li [(2b) Ti ]:
Yield:
quantitative.
54 36 12 24 4 2
C H Br O Li Ti
J
H,H = 2.5 Hz, 1 H, Harom), 3.63 (s, 3 H, CH
3
); dimer (minor com-
4
6
2
–
1
(
2151.2 g·mol )·8MeOH: calcd. C 30.93, H 2.85%; found: C 31.34,
pound): δ = 6.72–6.68 (m, 1 H, Harom), 6.52–6.48 (m, 1 H, Harom),
1
4
H 2.686%. H NMR (400 MHz, [D ]MeOH, 25 °C): dimer (major
compound): δ = 7.37 (s, 1 H, Harom), 3.69–3.59 (m, 1 H, CH CH ),
3
3.06 (s, 3 H, CH ). MS (ESI-FTMS, pos.): m/z calcd. for
+
+Li+); found:
C
48
H30Br
6
O24Li
5
Ti
2
(dimer): 1600.59195 (M
D
2
3
3.25–3.16 (m, 1 H, CH
2
CH3), 1.08 (t, 3
JH,H = 7.1 Hz, 3 H, CH
3
);
1600.59497.
3
monomer (minor compound): δ = 7.37 (s, 1 H, Harom), 4.28 (q, JH,H
3
1
Li
4
[(2a)
6
Ti
2
]:
Yield:
quantitative.
C
48
H
24Br12
O
24Li
4
Ti
2
= 7.1 Hz, 1 H, CH
(400 MHz, [D ]DMSO, 25 °C): monomer (major compound): δ = 7.10
(s, 1 H, Harom), 4.11 (q, JH,H = 7.1 Hz, 1 H, CH
); monomer = 7.1 Hz, 1 H, CH ); dimer (minor compound): δ = 7.03 (s, 1 H,
H,H = 7.1 Hz, 1 H, CH ), both signals of the CH
group vanish in the baseline. MS (ESI-FTMS, pos.): m/z calcd. for
2 3 3
CH ), 1.33 (t, JH,H = 7.1 Hz, 1 H, CH ). H NMR
–1
(2067.0 g·mol )·4MeOH: calcd. C 28.45, H 1.84%; found: C 28.23,
6
1
3
3
H 1.976%. H NMR (300 MHz, [D
compound): δ = 7.35 (s, 1 H, Harom), 3.18 (s, 3 H, CH
minor compound): δ = 7.63 (s, 1 H, Harom), 3.82 (s, 3 H, CH
4
]MeOH, 25 °C): dimer (major
2 3
CH ), 1.19 (t, JH,H
3
3
3
(
3
).
]DMSO, 25 °C): monomer (major com-
pound): δ = 7.15 (s, 1 H, Harom), 3.69 (s, 3 H, CH ); dimer (minor
compound): δ = 7.13 (s, 1 H, Harom), 3.17 (s, 3 H, CH ). MS (ESI-
Harom), 1.26 (t,
J
3
2
1
H NMR (300 MHz, [D
6
+
+
3
C
54
H36Br12
O24Li
4
Ti
2
K
D
(dimer): 2190.09049 (M +K ); found:
3
2190.09035.
+
FTMS, pos.): m/z calcd. for
C
48
H
24Br12
O24Li
5
Ti
2
(dimer):
+
Li [(3b) Ti ]: Yield: quantitative. C H N O Li Ti (1474.4 g/mol)·
2074.04889 (M
D
+Li ); found: 2074.04688.
4
6
2
54 42
6
36
4
2
2
9H O: calcd. C 39.63, H 3.70, N 5.14%, found: C 39.91, H 3.762,
1
Li
4
[(3a)
6
Ti
2
]: Yield: quantitative.
C
48
H
30
N
6
O
36Li
4
Ti
2
(1390.27 g· N 4.61%. H NMR (400 MHz, [D
4
]MeOH, 25 °C): monomer (major
–
1
4
mol )·13H
2
O: calcd. C 35.49, H 3.47, N 5.17%; found: C 35.32, H
compound): δ = 7.39 (d, JH,H = 2.6 Hz, 1 H, Harom), 4.38–4.26 (m,
Z. Anorg. Allg. Chem. 2015, 2222–2227
2226
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Journal of Inorganic and General Chemistry
www.zaac.wiley-vch.de
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
2
H, CH
2
CH
3
), 1.42–1.30 (m, 3 H, CH
3
), the other aromatic signal
K. Rissanen, R. Fröhlich, Inorg. Chim. Acta 2002, 25–32; c) A. K.
Das, A. Rueda, L. R. Falvello, S.-M. Peng, S. Batthacharya, In-
org. Chem. 1999, 38, 4365–4368; d) J. Heinicke, N. Peulecke, K.
Karaghiosoff, P. Mayer, Inorg. Chem. 2005, 44, 2137–2139.
5] G. Bauer, Z. Benk o˝ , J. Nuss, M. Nieger, D. Gudat, Chem. Eur. J.
overlaps with the aromatic signal of the monomer; dimer (minor com-
pound): δ = 7.24 (d, JH,H = 2.6 Hz, 1 H, Harom), 3.77–3.66 (m, 1 H,
4
), 1.00 (t, 3JH,H = 7.2 Hz, 3 H,
3 2 3
), 3.25–3.14 (m, 1 H, CH CH
CH
CH
2
CH
), the other aromatic signal overlaps with the aromatic signal of
[
[
3
2010, 16, 12091–12095.
1
the dimer. H NMR (400 MHz, [D
6
]DMSO, 25 °C): monomer δ = 7.93
d, JH,H = 2.8 Hz, 1 H, Harom), 6.93 (d, 4JH,H = 2.8 Hz, 1 H, Harom),
6] a) X. Sun, J. W. Darren, D. Caulder, R. E. Powers, K. N. Ray-
mond, E. H. Wong, Angew. Chem. 1999, 111, 1386–1390; Angew.
Chem. Int. Ed. 1999, 38, 1303–1306; b) X. Sun, D. W. Johnson,
D. Caulder, K. N. Raymond, H. E. Wong, J. Am. Chem. Soc.
2001, 123, 2752–2763; c) X. Sun, D. W. Johnson, K. N. Ray-
mond, H. E. Wong, Inorg. Chem. 2001, 40, 4504–4506; d) Y. Sak-
ata, S. Hiraoka, M. Shionoya, Chem. Eur. J. 2010, 16, 3318–3325;
e) S. Hiraoka, Y. Sakata, M. Shionoya, J. Am. Chem. Soc. 2008,
130, 10058–10059.
4
(
4
CH
.17 (q, 3JH,H = 7.1 Hz, 2 H, CH
CH
3
); dimer was not observed. MS (ESI-FTMS, neg.): m/z calcd. for
), 1.21 (t, 3JH,H = 7.1 Hz, 3 H,
3
2
27 21 3 M
C H N O -Li ); found:
18LiTi– (monomer): 730.04651 (M
+
730.08777.
–
1
Li
4
[(5b)
O: calcd. C 59.29, H 4.98%; found: C 59.37, H 4.716%. H NMR
300 MHz, [D ]MeOH, 25 °C): dimer (major compound): δ = 7.51–
6 2 72 4 2
Ti ]: Yield: quantitative. C90H O24Li Ti (1661.0 g·mol )
1
·9H
2
[
[
7] a) M. Baumert, M. Albrecht, H. D. F. Winkler, C. A. Schalley,
Synthesis 2010, 6, 953–958; b) M. Albrecht, M. Baumert, H. D. F.
Winkler, C. A. Schalley, R. Fröhlich, Dalton Trans. 2010, 39,
(
7
(
1
4
4
.42 (m, 2 H, Harom), 7.37 (d, JH,H = 2.2 Hz, 1 H, Harom), 7.34–7.25
4
m, 2 H, Harom), 7.20–7.12 (m, 1 H, Harom), 6.86 (d, JH,H = 2.2 Hz,
H, Harom), 3.71–3.57 (m, 1 H, CH CH ), 3.17–3.03 (m, 1 H,
), 0.79 (t, JH,H = 7.1 Hz, 3 H, CH ); monomer (minor com-
pound): δ = 7.57 (d, 4JH,H = 2.2 Hz, 1 H, Harom), 6.64 (d,
.2 Hz, 1 H, Harom), 4.04–3.96 (m, 2 H, CH CH ), 1.38–1.31 (m, 3 H,
CH ), the other aromatic signals lay under the signals of the dimer.
H NMR (300 MHz, [D ]DMSO, 25 °C): dimer (major compound): δ
6.83 (d, JH,H = 2.1 Hz, 1 H, Harom), 3.71–3.56 (m, 1 H, CH CH ),
.15–3.03 (m, 1 H, CH CH ), the
), 0.80 (t, 3JH,H = 7.0 Hz, 3 H, CH
7220–7222.
2
3
8] a) M. Albrecht, E. Isaak, M. Baumert, V. Gossen, G. Raabe, R.
Fröhlich, Angew. Chem. 2011, 123, 2903–2906; Angew. Chem.
Int. Ed. 2011, 50, 2850–2853; b) M. Albrecht, E. Isaak, V. Moha,
G. Raabe, R. Fröhlich, Chem. Eur. J. 2014, 20, 6650–6658; c) M.
Albrecht, E. Isaak, H. Shigemitsu, V. Moha, G. Raabe, R.
Fröhlich, Dalton Trans. 2014, 43, 14636–14643.
3
CH
2
CH
3
3
4
J
H,H
=
2
2
3
3
1
6
4
[9] D. J. Cram, J. M. Cram, Science 1974, 183, 803–809.
=
3
2
3
[
10] G. Abbiati, A. Doda, M. DellЈAcqua, V. Pirovano, D. Facoetti, S.
Rizzato, E. Rossi, J. Org. Chem. 2012, 77, 10461–10467.
2
3
3
other aromatic signals overlap with the ones of the monomer; mono-
[
[
11] F. v. Hemmelmayr, Monatsh. Chem. 1912, 33, 971–998.
12] a) B. Masjost, P. Ballmer, E. Borroni, G. Zuercher, F. K. Winkler,
R. Jakob-Roetne, F. Diederich, Chem. Eur. J. 2000, 6, 971–982;
b) M. Ellermann, R. Paulini, R. Jakob-Roetne, C. Lerner, E. Bor-
roni, D. Roth, A. Ehler, W. B. Schweizer, D. Schlatter, M. G. Ru-
dolph, F. Diederich, Chem. Eur. J. 2011, 17, 6369–6381; c) A.
Bolliger, F. Reuter, J. Proc. R. Soc. N.S.W. 1938, 72–73, 329–
4
mer (minor compound): δ = 6.50 (d, JH,H = 2.3 Hz, 1 H, Harom), 4.19
3
), 1.26 (t, 3JH,H = 7.1 Hz, 3 H, CH
(
q, JH,H = 7.1 Hz, 2 H, CH
2
CH
3
3
),
the other aromatic signals overlap with the ones of the dimer. MS (ESI-
+
72 4 2
FTMS, pos.): m/z calcd. for C90H O24Li Ti Na (dimer): 1683.39048
+
(
D
M +Na ); found: 1683.39587.
3
34.
13] N. K. Yee, L. J. Nummy, G. P. Roth, Bioorg. Med. Chem. Lett.
996, 6, 2279–2280.
[
References
1
[
[
1] J. Watson, F. Crick, Nature 1953, 171, 737–738.
[14] a) A. R. Penfold, G. R. Ramage, J. L. Simonson, J. Chem. Soc.
1938, 756–758; b) B. van‘Riet, G. L. Wampler, H. L. Elford, J.
Med. Chem. 1979, 22, 589–592.
[15] M. Albrecht, M. Fiege, M. Baumert, M. de Groot, R. Fröhlich, L.
Russo, K. Rissanen, Eur. J. Inorg. Chem. 2007, 609–616.
2] a) J.-M. Lehn, A. Rigault, J. Siegel, J. Harrowfield, B. Chevrier,
D. Moras, Proc. Natl. Acad. Sci. USA 1987, 84, 2565–2569; b)
C. Piguet, G. Bernardinelli, G. Hopfgartner, Chem. Rev. 1997, 97,
2005–2062; c) M. Albrecht, Chem. Rev. 2001, 101, 3457–3497.
[
3] a) M. Albrecht, S. Mirtschin, M. de Groot, I. Janser, J. Runsink, [16] CrysAlisPro, Version 1.171.36.31, Agilent Technologies, Yarnton,
G. Raabe, M. Kogej, C. A. Schalley, R. Fröhlich, J. Am. Chem.
Oxfordshire, UK, 2012.
Soc. 2005, 127, 10371–10387. Other examples of helicates in- [17] R. C. Clark, J. S. Reid, Acta Crystallogr., Sect. A 1995, 51, 887–
volving titanium ions: ; b) D. M. Weekes, C. Diebold, P. Mobian,
897.
C. Huguenard, L. Allouche, M. Henry, Chem. Eur. J. 2014, 20,
[18] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112.
[19] O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard, H.
Puschmann, J. Appl. Crystallogr. 2009, 42, 339.
5092–5101; c) F. E. Hahn, T. Kreickmann, T. Pape, Dalton Trans.
2006, 769–771; d) F. E. Hahn, B. Birkmann, T. Pape, Dalton
Trans. 2008, 2100–2102.
4] a) M. Albrecht, K. Witt, H. Röttele, R. Fröhlich, Chem. Commun.
[
Received: June 24, 2015
2001, 1330–1331; b) M. Albrecht, K. Witt, P. Weis, E. Wegelius,
Published Online: September 7, 2015
Z. Anorg. Allg. Chem. 2015, 2222–2227
2227
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim