Synthesis and characterization of [Mo3S4(NDABu) (HNDABu)2]3- and [Mo3S4(HNDAPr) 3]2- anions as building blocks for organic-inorganic hybrid solids

Article abstract of DOI:10.1002/ejic.201201253

The polymetallic cation [Mo₃S₄(H₂O) ₉]⁴⁺ was used as an inorganic precursor to generate new hybrid organic-inorganic chalcogenide clusters. Three organic compounds with flexible and hanging arms were synthesized and investigated as ligands for coordination complexes with the rigid and electroactive inorganic {Mo ₃S₄} unit. Interestingly, the {Mo₃S ₄} core formed hybrid structures with the flexible H₃NDABu [N-(3-carboxypropyl)iminodiacetic acid] and H₃NDAPr [N-(2-carboxyethyl)iminodiacetic acid] ligands, which were characterized by X-ray crystallography. Surprisingly, no crystals were isolated, when the more rigid H₃NDABn [N-(4-methoxycarbonylbenzyl)iminodiacetic acid] ligand was used. The two coordination complexes [Mo₃S₄(NDABu) (HNDABu)₂]^3- and [Mo₃S₄(HNDAPr) ₃]^2- were characterized by X-ray diffraction (XRD), IR spectroscopy, thermal gravimetric analysis (TGA), ¹H NMR spectroscopy, elemental analysis, and electrochemistry. The organic ligands H₃NDABu, H₃NDAPr, and H₃NDABn were characterized by XRD, IR, HR mass, and ¹³C and ¹H NMR spectroscopy. [Mo₃S₄(NDABu)(HNDABu)₂] ^3- and [Mo₃S₄(HNDAPr)₃]^2- constitute promising preformed building blocks to generate new organic-inorganic hybrid molecular or extended materials. Two new promising preformed building blocks [Mo₃S₄(NDABu)(HNDABu) ₂]^3- and [Mo₃S₄(HNDAPr) ₃]^2- have been obtained. Their syntheses and characterizations are described. Copyright

Full text of DOI:10.1002/ejic.201201253

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DOI:10.1002/ejic.201201253
Synthesis and Characterization of [Mo3S4(NDABu)-
(HNDABu)2]3– and [Mo3S4(HNDAPr)3]2– Anions as
Building Blocks for Organic–Inorganic Hybrid Solids
Sylvain Duval,[a] Frédéric Dumur,[b] Laure Guénée,[c]
Jérôme Marrot,[a] Corine Simonnet-Jégat,*[a] and
Emmanuel Cadot[a]
Keywords: Polychalcogenides / Cluster compounds / Molybdenum / Carboxylate ligands / Organic–inorganic hybrid
composites
The polymetallic cation [Mo3S4(H2O)9]4+ was used as an inor-
ganic precursor to generate new hybrid organic–inorganic
chalcogenide clusters. Three organic compounds with flexi-
ble and hanging arms were synthesized and investigated as
ligands for coordination complexes with the rigid and elec-
troactive inorganic {Mo3S4} unit. Interestingly, the {Mo3S4}
core formed hybrid structures with the flexible H3NDABu [N-
(3-carboxypropyl)iminodiacetic acid] and H3NDAPr [N-(2-
carboxyethyl)iminodiacetic acid] ligands, which were char-
acterized by X-ray crystallography. Surprisingly, no crystals
were isolated, when the more rigid H3NDABn [N-(4-meth-
oxycarbonylbenzyl)iminodiacetic acid] ligand was used. The
two coordination complexes [Mo3S4(NDABu)(HNDABu)2]3–
and [Mo3S4(HNDAPr)3]2– were characterized by X-ray dif-
fraction (XRD), IR spectroscopy, thermal gravimetric analysis
(TGA), 1H NMR spectroscopy, elemental analysis, and elec-
trochemistry. The organic ligands H3NDABu, H3NDAPr, and
H3NDABn were characterized by XRD, IR, HR mass, and 13
C
and 1H NMR spectroscopy. [Mo3S4(NDABu)(HNDABu)2]3–
and [Mo3S4(HNDAPr)3]2– constitute promising preformed
building blocks to generate new organic–inorganic hybrid
molecular or extended materials.
size, and charge.[9] Triangular chalcogenide-bridged clusters
such as [M3S4(H2O)9]4+ (M = Mo or W) are also good can-
didates to generate organic–inorganic hybrid materials.[10]
We previously described the use of the triangular chalco-
genide-bridged cluster [Mo3S4(HNTA)3]2– (NTA3– = ni-
trilotriacetate) as a preformed building block to generate
metal–organic materials.[11] Interestingly, this cluster con-
tains three hanging carboxylates and six carbonyl functions
that are available for further coordination to an electro-
philic species. The 3D networks, which result from the clus-
ter [Mo3S4(HNTA)3]2– and the La3+ cation, La2Cl-
[Mo3S4(NTA)3]·17H2O[12] and La0.75Cl0.25[Mo3S4(HNTA)3]·
18H2O[13] have been described. Under mild synthetic condi-
tions (room temperature and ambient pressure), the hang-
ing carboxylate functions are not coordinated with the La3+
cations in La0.75Cl0.25[Mo3S4(HNTA)3]·18H2O. In contrast,
in the 3D network La2Cl[Mo3S4(NTA)3]·17H2O, which is
Introduction
Organic–inorganic hybrid materials represent a wide and
versatile class of compounds with potential applications
ranging from medicine and biology[1] to catalysis,[2] gas
storage or separation,[3,4] electrical conductivity,[5] and mag-
netism.[6] Investigations concerning the structure, design,
and control of the architecture have become major chal-
lenges in this field. The main goals are always to obtain
compounds with the required structures and properties and
to start from well-designed building blocks. During the last
decade, much work has been devoted to the synthesis of
such materials through the modification of organic ligands
and inorganic clusters.[7,8] In this context, polyoxometalate
(POM) clusters were revealed as good inorganic building
blocks because of the diversity in their composition, shape,
[a] Institut Lavoisier de Versailles, UMR CNRS 8180, Université obtained under hydrothermal synthesis conditions, the free
carboxylate functions are coordinated to the La3+ cations.
de Versailles-St-Quentin,
45 Avenue des Etats-Unis, 78035 Versailles, France
The self-condensation process of the [Mo2O2S2(OH2)6]2+
Fax: +33-1-39254452
E-mail: corine.simonnet@uvsq.fr
cation in the presence of the structuring agent
[Mo3S4(HNTA)3]2– allowed us to isolate the largest oxo-
thiomolybdenum ring, which consists of an {Mo18} cyclic
arrangement built around.[14] These first results undoubt-
edly demonstrated the potential of this cluster
[Mo3S4(HNTA)3]2– and its derivatized species as valuable
[b] Aix-Marseille Université, CNRS, Institut de Chimie
Radicalaire, UMR 7273,
13397 Marseille, France
[c] Laboratory of X-ray Crystallography, University of Geneva,
24 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201201253.
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preformed building blocks. In light of these promising re-
Results and Discussion
sults, we aimed to modify the cluster by varying its organic
part and to determine how the resulting metal–organic ma-
terial and its corresponding properties could be affected by
this modification. To obtain some further insight about the
Synthesis of the Ligands
The three ligands H3NDABu, H3NDAPr, and
influence of the spacer in the organic part, we chose to in- H3NDABn were prepared by N-alkylation of the corre-
vestigate a series of H3NTA analogues with notably two sponding amino acids. Two synthetic pathways were investi-
ligands with flexible alkyl chains, that is, H3NDABu [N-(3- gated for the synthesis of the ligand H3NDABu. The first
carboxypropyl)iminodiacetic acid], H3NDAPr [N-(2-carb- one involved a three-step approach in which 4-aminobutyric
oxyethyl)iminodiacetic acid], and the more rigid H3NDABn acid (1) was esterified first under acidic conditions with
[N-(4-methoxycarbonylbenzyl)iminodiacetic acid], which methanol to give methyl 4-aminobutyrate (2), which under-
incorporates an aromatic ring in its backbone.
went N-alkylation upon treatment with 2 equiv. of methyl
The syntheses and structures of the organic precursors bromoacetate (3, see Scheme 1). Finally, under basic condi-
to H3NDABu, H3NDAPr, and H3NDABn as well as of the tions, the hydrolysis of triester 4 furnished the tripodal li-
resulting coordination complexes [Mo3S4(NDABu)(HND- gand H3NDABu in low yield. Surprisingly, the cleavage of
ABu)2]3– and [Mo3S4(HNDAPr)3]2– are described. The syn- the three ester groups in 4 proved to be more difficult than
thesis of [Mo3S4(HNDABn)3]2–, which includes a more ri- anticipated, and the synthesis of the ligand could only be
gid spacer, is also reported.
accomplished by using a large excess amount of potassium
Scheme 1. Two pathways investigated for the H3NDABu and H3NDAPr syntheses.
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Scheme 2. Synthesis of H3NDABn.
hydroxide. Thus, H3NDABu was recovered contaminated sic solution of the tricarboxylic ligands to an acidic solution
with a non-negligible amount of potassium chloride. This of (NH4)2[Mo3S4Cl6(H2O)3] provided the clusters
problem was resolved in the second strategy in which the N- [Mo3S4(NDABu)(HNDABu)2]3–
(C1)
and
[Mo3S4
alkylation of the terminal amine was successfully achieved (HNDAPr)3]2– (C2) in approximately 40% yield from
without the protection of the acid groups.[15] The desired H3NDABu and H3NDAPr, respectively; the cluster
ligand H3NDABu was isolated in pure form in 60% yield [Mo3S4(HNDABn)3]2– (C3) was provided in 60% from the
by the direct reaction under basic conditions between bro- more rigid H3NDABn ligand. Crystals suitable for X-ray
moacetic acid and 4-aminobutyric acid. By using this sec- crystal structure analyses were obtained for the two clusters
ond synthetic approach, H3NDAPr was prepared from 3- C1 and C2; C3 was not soluble enough to isolate crystals
aminopropanoic acid (6) and obtained with a much higher and record NMR spectra. It was characterized by IR spec-
yield (79%) than previously reported (60%).[16] By using a troscopy, thermal gravimetric analysis (TGA), elemental
procedure similar to that of the first synthetic approach for analysis, and ESI-MS.
H3NDABu, the third ligand H3NDABn was prepared in
three steps starting from 4-(aminomethyl)benzoic acid (7,
see Scheme 2).
Structures of the Coordination Complexes
To assess the effective structure of the three organic li-
gands, suitable crystals of H3NDABr, H3NDABu, and
The X-ray crystallographic study of C1 revealed that the
H3NDABn were obtained by slow concentration of mixed structure consists as a discrete trianionic cluster with two
solutions of methanol and water, and the X-ray solid-state sodium cations and one cesium cation. The unit cell also
structures were determined (see Figure 1).
contains nine water molecules. For C2, the X-ray diffraction
(XRD) study revealed that the structure consists of a dis-
crete dianionic cluster with one sodium cation and one po-
tassium cation. This unit cell also contains water molecules.
The structures of the anions are shown in Figure 2, and
the selected interatomic distances and angles for the two
anions are collected in Table 1. The triangular core
{Mo3S4} of the anions in which each molybdenum atom is
octahedrally coordinated by three sulfur atoms along with
one nitrogen and two oxygen atoms from the ligand pres-
ents classical bond lengths and angles (see Table 1).[10] For
C1, two of the free hanging carboxylate ligands are proton-
ated, as shown by lengths of carbon–oxygen distances that
are different in ligands A and B [C–O range: 1.209(8)–
1.326(7) Å] and nearly equal in ligand C [C–O 1.260(7) and
1.265(7) Å]. Bond valence sum calculations on the three
molybdenum atoms belonging to the central cluster show
evidence of a +IV oxidation state for each atom (for MoA
ca. 4.03, MoB ca. 3.99, and MoC ca. 3.99). Thus, the central
cluster charge is {Mo3S4}4+. If we take account of the three
countercations in the global charge, one hanging carboxyl-
Figure 1. Views of (a) H3NDAPr, (b) H3NDABu, and
(c) H3NDABn as ball-and-stick representations (C = grey, N =
blue, O = red).
The three ligands were then engaged in a reaction with ate group of the complex has to be deprotonated to assure
the inorganic {Mo3S4} unit. Typically, the addition of a ba- the neutrality of the species, as shown by the average dis-
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tances of both of the C–O bonds in the functional group
(1.260 Å and 1.265 Å).[16] For C2, one of the free carboxyl-
ate groups is found disordered, and the two others are pro-
tonated [C–O range: 1.252(1)–1.221(1) Å]. This was con-
firmed by XRD analysis, which revealed two cations for C2.
We obtained only a few crystals of C2; however, NMR and
IR spectroscopy as well as TGA and elemental analyses
were performed on the most abundant powder of Na2-
[Mo3S4(HNDAPr)3]·8H2O.
Figure 2. Views of the [Mo3S4(NDABu)(HNDABu)2]3– (C1) and
[Mo3S4(HNDAPr)3]2– (C2) anions: (a) ball-and-stick representa-
tion showing the octahedral coordination of the molybdenum
atoms (C = grey, N = blue, O = red, S = yellow, Mo = green);
(b) mixed polyhedral ball-and-stick representation of the free hang-
ing carboxylate groups.
Figure 3. 1H NMR spectra in [D6]DMSO of (a) [Mo3S4-
(HNDAPr)3]2– (C2) and (b) [Mo3S4(NDABu) (HNDABu)2]3– (C1).
ing to the two methylene groups of the free hanging carb-
oxylate. The two doublets centered at δ = 4.32 and
3.96 ppm (J = 15.7 Hz) are attributed to the coupled dia-
stereotopic protons of the methylene groups belonging to
the acetate fragments coordinated to the {Mo3S4} moiety.
The IR spectra of C1 and C2 show two types of carb-
oxylate groups, that is, those attached to the {Mo3S4} core
and the free hanging carboxylates, which are revealed at
1631 cm–1 by a strong absorption with a shoulder at
1529 cm–1, respectively, for C1 and at 1716 (shoulder) and
1625 cm–1 (strong absorption), respectively, for C2. Other
absorptions can be assigned as the νas(OCO) of the ni-
triloacetic ligands. The νs(OCO) are observed at 1465 and
1390 cm–1 and 1462 and 1389 cm–1, respectively, for C1 and
Table 1. Selected interatomic distances [Å] and angles [°] for
Na2Cs[Mo3S4(NDABu)(HNDABu)2]·9H2O (C1) and for NaK-
[Mo3S4(HNDAPr)3]·3.5 H2O (C2).
Distances [Å] and
angles [°]
C1
C2
Mo–Mo
Mo–(μ3S)
Mo–(μS)
Mo–N
Mo–O
2.7421(7)–2.7521(7)
2.335(1)–2.345(1)
2.284(1)–2.299(1)
2.290(5)–2.298(4)
2.119(4)–2.147(4)
71.75(4)–72.02(4)
73.48(4)–73.87(5)
2.7533(6)–2.7641(8)
2.325(1)–2.334(2)
2.291(1)–2.306(1)
2.305(5)–2.317(7)
2.112(4)–2.140(4)
72.46(1)–72.94(1)
73.64(1)–73.79(4)
Mo–(μ3-S)–Mo
Mo–(μ-S)–Mo
1
The H NMR spectrum in [D6]DMSO of C1 contains C2. For C3, only one type of carboxylate group is observed
the signals of the coordinated H3NDABu ligand (see Fig- with absorptions at 1614 and 1385 cm–1. Several absorp-
ure 3b). The two doublets centered at δ = 4.35 and tions between 600 and 400 cm–1 could be attributed to
4.00 ppm are attributed to the coupled diastereotopic pro- ν(Mo–S).
tons (J = 16.0 Hz) of the two methylene groups belonging
The electrochemical properties of compounds C1 and C2
to the acetate fragments coordinated to the {Mo3S4} moi- were studied by cyclic voltammetry in a pH = 7 buffer and,
ety.
under the same conditions, were compared with those of
The singlet at δ = 2.15 ppm (12 H) is due to two of the [Mo3S4(NTA)3]5–. As previously reported in the literature,
methylene groups of the free hanging carboxylate, and the all of the compounds exhibited one reversible redox couple
remaining signal for the third methylene group is over- assigned to the first reduction state of the {Mo3S4} clus-
lapped with the doublet at δ = 4.35 ppm. The H NMR ter.[11,14] The redox potentials E° (mean values between the
1
spectrum in DMSO of C2 (see Figure 3a) shows two triplets cathodic and anodic peak potentials) are very similar for
at δ = 4.65 and 3.03 ppm (J = 6.4 and 7.4 Hz) correspond- the three compounds {–0.55 V for [Mo3S4(NTA)3]5–,
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–0.57 V for [Mo3S4(NDAPr)3]5–, and –0.61 V for
[Mo3S4(NDABu)3]5–}, which is evidence of the weak influ-
ence of the ligands on the reduction of MoIV and of a pu-
rely metal-centered reduction process (see Figure 4).
= 77.0 ppm, respectively. Infrared spectra were recorded with an
FTIR Magna 550 Nicolet spectrophotometer by using the tech-
nique of pressed KBr pellets.
X-ray Crystal Structure Determination: Intensity measurements for
C1 were carried out with a Bruker X8 diffractometer equipped with
a CCD bidimensional detector using monochromatized Mo-Kα ra-
diation (λ = 0.71073 Å). Selected crystal data and details of the
data collection for the cluster are given in Table 2. An absorption
correction was applied by using the SADABS program[17] based on
the Blessing method.[18] The structures were solved by direct meth-
ods followed by Fourier difference syntheses using the SHELXTL
package. All atoms, with the exception of the hydrogen atoms, were
anisotropically refined. The final reliability factors converged to R1
= 0.0356 and wR2 = 0.0903. Selected interatomic distances [Å] are
given in Table 1. Intensity measurements for H3NDABu,
H3NDAPr, H3NDABn, and NaK[Mo3S4(HNDAPr)3]·3.5H2O were
carried out with an Agilent Supernova diffractometer equipped
with a CCD bidimensional detector by using monochromatized
Cu-Kα radiation (λ = 1.54184 Å). Selected crystal data and struc-
ture refinement details are given in Table 2. Analytical numeric ab-
sorption corrections by using a multifaceted crystal model were
made on the basis of expressions derived by Clark and Reid.[19] The
structures were solved by direct methods (SHELXS[20] or SIR97[21]
programs) followed by Fourier difference syntheses using the
SHELX package.[19] CCDC-866115 (for C1), -886520 (for
H3NDABu), -886521 (for H3NDAPr), -886522 (for H3NDABn),
and -886523 (for C2) 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.
Figure 4. Cyclic voltammograms of 0.2 mm solutions of deproton-
ated clusters [Mo3S4(NDABu)3]5–, [Mo3S4(NTA)3]5–, and
[Mo3S4(NDAPr)3]5– obtained at pH = 7 [0.5 m Li2SO4 + 0.2 m tri-
s(hydroxymethyl)aminomethane + H2SO4] with a potential range
from +0.2 V to –0.9 V. The scan rate was 10 mVs–1. The working
electrode was glassy carbon, and the reference electrode was SCE
(saturated calomel electrode).
Electrochemical Data: These were obtained with an EG & G 273 A
driven by a PC with the M270 software. A one-compartment cell
with a standard three-electrode configuration was used for the cy-
clic voltammetry experiments. The composition of the supporting
electrolyte was 0.5 m Li2SO4 + 0.2 m tris(hydroxymethyl)amino-
methane + H2SO4 at pH = 7. The concentration of the clusters
was 0.2 mm. Prior to each experiment, the solutions were deaerated
thoroughly for at least 30 min with pure argon, and a positive pres-
sure of this gas was maintained during subsequent work. All cyclic
voltammograms were recorded at a scan rate of 10 mVs–1, unless
otherwise stated. All of the experiments were performed at room
temperature, which was controlled and set for the laboratory at
20 °C. The reference electrode was a saturated calomel electrode
(SCE), and platinum gauze with a large surface area was used as a
counter electrode. Both electrodes were separated from the bulk
electrolyte solution by fritted compartments filled with the same
electrolyte. The working electrode was a 3 mm o.d. glassy carbon
disc (GC, Le Carbone de Lorraine, France).
Conclusions
A series of iminodiacetic acid derivatives have been pre-
pared and investigated as new hanging arms for hybrid or-
ganic–inorganic clusters. The two new clusters
Na2Cs[Mo3S4(NDABu)(HNDABu)2]·9H2O and NaK-
[Mo3S4(HNDAPr)3]·3.5H2O were synthesized and charac-
terized. In future work, attempts to coordinate the remain-
ing free carboxylates to various transition metals will be
carried out for the construction of 3D networks. Coordina-
tion of these clusters to other metals could generate hetero-
metallic hybrid clusters with new capabilities.
Experimental Section
Characterization Techniques: Elemental analyses were performed by
the Service Central d’Analyse du CNRS. Mass spectrometry was
performed by the Spectropole of Aix-Marseille University (Mar-
seille). ESI mass spectral analyses were performed with a 3200
QTRAP (Applied Biosystems SCIEX) mass spectrometer. The HR
mass spectral analyses were performed with a QStar Elite (Applied
Biosystems SCIEX) mass spectrometer. The water content corre-
sponding to the weight loss up to about 250 °C was determined by
TGA using a TGA-7 Perkin–Elmer apparatus. The 1H and 13C
NMR spectroscopic data were recorded at room temperature in
5 mm o.d. tubes with either a Bruker Avance 300 spectrometer
equipped with a QNP probe head or a Bruker Avance 400 spec-
trometer (Spectropole, Aix-Marseille University; 1H NMR at
400 MHz, 13C NMR at 100 MHz). The 1H and 13C NMR chemical
shifts were referenced to the CDCl3 solvent peak at δ = 7.26 and δ
Synthesis Procedures: The precursors (NH4)2[Mo3S4Cl6(H2O)3] and
Na2[Mo3S4(HNTA)3]·7H2O were synthesized according to pre-
viously reported procedures without any modifications and with
similar yields.[11] All of the reagents were purchased from Aldrich
and Alfa Aesar with the best purity available and used as received.
Methyl 4-aminobutanoate (2) was prepared according to a litera-
ture procedure.[22]
Methyl 4-[Bis(2-methoxy-2-oxoethyl)amino]butanoate (4): To a solu-
tion of methyl 4-aminobutanoate (2, 0.70 g, 6 mmol) in absolute
ethanol were successively added methyl bromoacetate (3, 1.13 mL,
12 mmol) and potassium carbonate (1.24 g, 9 mmol), and the reac-
tion mixture was heated at reflux for 24 h. The solution was filtered
to remove the excess amount of K2CO3, and the solid was washed
with diethyl ether. The solution was transferred back to a round-
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Table 2. Crystal and structure refinement data for H3NDABu, H3NDAPr, H3NDABn, Na2Cs[Mo3S4(NDABu)(HNDABu)2]·9H2O (C1),
and NaK[Mo3S4(HNDAPr)3]·3.5H2O (C2).
H3NDABu
C8H13NO6
H3NDAPr
C7H11NO6
H3NDABn
C12H13NO6
C2
C1
Empirical formula
C21H30KMo3N3-
NaO23.50S4
298
1.54184
orthorhombic
C24H50CsMo3N3-
Na2O27S4
100
Temperature [K]
Wavelength [Å]
Crystal system
Crystal size
Space group
a [Å]
b [Å]
c [Å]
α [°]
180
1.54184
monoclinic
180
1.54184
monoclinic
180
1.54184
orthorhombic
1.54184
monoclinic
0.16ϫ0.08ϫ0.02
P21/c
17.6609(7)
12.5186(5)
21.7666(9)
90
0.41ϫ0.19ϫ0.10 0.32ϫ0.15ϫ0.12 0.25ϫ0.09ϫ0.05 0.21ϫ0.15ϫ0.09
P21/c
14.1353(2)
12.2120(2)
6.51379(9)
90
P21/c
Pbca
Cmca
5.43300(10)
13.7838(3)
12.0704(3)
90
26.1283(3)
6.67291(9)
27.6461(4)
90
15.0340(4)
26.9497(5)
22.6446(5)
90
β [°]
92.1575(14)
90
1123.62(3)
4
1.627
4.425
107.261(2)
90
863.21(3)
4
1.579
1.220
90
90
90
90
9174.7(4)
8
1.707
110.631(2)
90
4503.7(3)
4
2.001
1.916
γ [°]
V [Å3]
4820.13(11)
16
1.473
Z
Dcald.c [gcm–3]
μ [mm–1]
1.024
9.922
θ limits [°]
Reflections collected
Independent reflections
R(int)
Final R indices
[I Ͼ 2σ(I)]
R indices
3.13/73.37
6336
2205
5.00/73.37
3114
1691
3.20/73.45
10821
4727
3.28/73.30
11100
4687
1.23/25.00
57585
7824
0.0209
0.0107
0.0214
0.0330
0.0704
R1 = 0.0279
wR2 = 0.0733
R1 = 0.0285
wR2 = 0.0737
2205/0/167
R1 = 0.0327
wR2 = 0.0832
R1 = 0.0339
wR2 = 0.0840
1691/0/139
0.260/–0.200
1.111
R1 = 0.0369
wR2 = 0.0954
R1 = 0.0459
wR2 = 0.1019
4727/0/388
0.242/–0.266
1.027
R1 = 0.0683
wR2 = 0.2146
R1 = 0.0732
wR2 = 0.2265
4687/1/277
2.904/–1.412
1.371
R1 = 0.0356
wR2 = 0.0903
R1 = 0.0603
wR2 = 0.1055
7824/0/579
0.998/–0.677
1.087
(all data)
Data/restraints/parameters
Residual electron density [eÅ–3] 0.273/–0.364
Goodness-of-fit
1.106
bottomed flask, and the solvent was removed under reduced pres-
sure. The resulting oil was purified by column chromatography
(SiO2, CH2Cl2/acetone) to give the triester (1.38 g, 88%) as a light
(6 m solution). After several days, the product precipitated from the
solution. The precipitate was removed by filtration and recrys-
tallized from water to give H3NDABu (6.97 g, 60%). 1H NMR
(400 MHz, D2O): δ = 3.74 (s, 4 H), 3.19 (t, J = 7.8 Hz, 2 H), 2.28
(t, J = 7.0 Hz, 2 H), 1.98–1.75 (m, 2 H) ppm. 13C NMR (100 MHz,
1
yellow oil. H NMR (400 MHz, CDCl3): δ = 3.75 (s, 6 H), 3.68 (s,
3 H), 3.56 (s, 4 H), 2.76 (t, 2 H, J = 6.1 Hz), 2.40 (t, 2 H, J =
7.3 Hz), 1.80 (q, 2 H, J = 7.1 Hz) ppm. 13C NMR (100 MHz,
D O): δ = 180.1, 170.6, 57.0, 55.9, 33.3, 20.4 ppm. IR: ν = 324 (w),
˜
2
CDCl3): δ = 173.9, 171.6, 54.7, 53.4, 51.5, 31.3, 23.1 ppm. HRMS 352 (w), 556 (m), 702 (m), 914 (m), 959 (w), 988 (w), 1103 (w),
(ESI): calcd. for [M + H]+ 262.1285; found 262.1287.
1208 (m), 1711 (C=O, sh), 1628 (br. s) 1581 (sh), 1473 (sh), 1400
(s), 1362 (sh), 1332 (m) cm–1. HRMS (ESI): calcd. for [M – H]–
218.0670; found 218.0669.
4-[Bis(carboxymethyl)amino]butanoic Acid (H3NDABu)
(a) Hydrolysis of 4: To a solution of KOH (9 g, 225 mmol) in H2O
(25 mL) and ethanol (25 mL) was added 4 (8.36 g, 32 mmol), and
the solution was heated at reflux for 48 h. After removal of the
volatiles, the remaining aqueous layer was acidified to pH = 5 with
a diluted aqueous HCl solution. The aqueous phase was extracted
with diethyl ether (3ϫ 100 mL) to remove all of the organic impuri-
ties. The aqueous phase was concentrated to dryness in a rotary
evaporator. To remove the potassium chloride, the white solid was
recrystallized several times from methanol. The title compound
(2.95 g, 42%) was obtained as a white solid.
3-[Bis(carboxymethyl)amino]propanoic Acid (H3NDAPr): Com-
pound 5 (7.36 g, 53 mmol) in H2O (50 mL) was neutralized by add-
ing KOH (3.24 g, 58 mmol) under nitrogen at room temperature
over a period of 20 min. To this solution was added 3-aminopropa-
noic acid (6, β-alanine, 2.32 g, 26 mmol), which was neutralized
with KOH (1.53 g, 26 mmol). The mixture was heated at reflux
under nitrogen for 5 h, and KOH (3.14 g, 56 mmol) was added over
the first 30 min of heating. The solution was cooled to room tem-
perature, and the pH was adjusted to 6.5 by the addition of HCl
(6 m solution). The solution was concentrated under vacuum, until
a white precipitate of potassium salts appeared. The solid was re-
moved by filtration, and the pH of the resulting solution was ad-
(b) Direct Synthesis from 4-Aminobutanoic Acid (1): Bromoacetic
acid (5, 7.24 g, 53 mmol) in H2O (50 mL) was neutralized by add-
ing KOH (3.24 g, 55 mmol) under nitrogen at room temperature justed to 2.5 by the addition of HCl (6 m solution). After several
over a period of 20 min. To this solution was added 1 (2.68 g,
26 mmol), which was neutralized with KOH (1.53 g, 26 mmol). The
mixture was heated at reflux under nitrogen for 5 h, and KOH
(3.14 g, 53 mmol) was added over the first 30 min of heating. The
solution was cooled to room temperature, and the pH was adjusted
to 6 by the addition of HCl (6 m solution). The solution was con-
centrated under vacuum, until a white precipitate of potassium
salts appeared. The solid was removed by filtration, and the pH of
the resulting solution was adjusted to 2.5 by the addition of HCl
days, the product precipitated from the solution, and the precipitate
was removed by filtration and then dried under vacuum to give
1
H3NDAPr (4.2 g, 79%). H NMR (400 MHz, D2O): δ = 3.84 (s, 4
H), 3.49 (t, J = 8.1 Hz, 2 H), 2.79 (t, J = 8.1 Hz, 2 H) ppm. 13C
NMR (100 MHz, D2O): δ = 174.1, 169.7, 56.9, 51.8, 29.0 ppm. IR:
ν = 1720 (s), 1624 (s), 1462 (m), 1442 (m), 1401 (s), 1377 (s), 1322
˜
(s), 1257 (s), 1181 (m), 979 (m), 955 (m), 853 (m), 809 (m), 697 (m),
598 (w), 543 (w), 476 (w), 427 (w) cm–1. HRMS (ESI): calcd. for
[M + H]+ 206.0659; found 206.0654.
Eur. J. Inorg. Chem. 2013, 1149–1156
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1
Methyl 4-(Aminomethyl)benzoate (8):[23] To a solution of 4-(ami-
nomethyl)benzoic acid (7, 10 g, 66 mmol) in methanol (250 mL)
was slowly added concentrated H2SO4 (2 mL), and the reaction
mixture was heated at reflux overnight. After cooling, the solvent
was removed under reduced pressure, which yielded a yellowish
residue. The residue was neutralized by the addition of a diluted
aqueous NaOH solution, and the ester was extracted with ethyl
acetate (3ϫ 100 mL). The combined organic phases were dried
with magnesium sulfate, and the solvent was removed under re-
duced pressure. The resulting residue was purified by filtration
through a plug of silica gel (ethyl acetate) to give 8 (8.52 g, 78%),
which was used in the next step without any further purification.
1H NMR (400 MHz, [D6]DMSO): δ = 7.90 (d, J = 8.1 Hz, 2 H),
7.47 (d, J = 8.1 Hz, 2 H), 3.84 (s, 3 H, OCH3), 3.80 (s, 2 H, CH2),
85%). H NMR (400 MHz, D2O): δ = 3.86 (s, 4 H), 4.54 (s, 2 H),
7.63 (d, J = 8.1 Hz, 2 H), 8.04 (d, J = 8.1 Hz, 2 H) ppm. 1H NMR
(400 MHz, [D6]DMSO): δ = 3.38 (s, 4 H), 3.89 (s, 2 H), 7.43 (d, J
= 8.1 Hz, 2 H), 7.89 (d, J = 8.1 Hz, 2 H) ppm. 13C NMR
(100 MHz, D2O): δ = 56.2, 58.3, 130.2, 131.2, 132.7, 133.7, 170.1,
170.8 ppm. 13C NMR (100 MHz, [D6]DMSO): δ = 55.7, 56.8,
128.5, 129.3, 129.7, 144.3, 167.3, 173.2 ppm. IR: ν = 536 (w), 561
˜
(w), 643 (w), 668 (w), 698 (m), 774 (m), 812 (m), 907 (m), 1014 (w),
1265 (w), 1322 (w), 1386 (s), 1558 (s), 1623 (br. s), 1709 (m) cm–1.
HRMS (ESI): calcd. for [M + H]+ 268.0816; found 268.0821.
Synthesis of Na2Cs[Mo3S4(NDABu)(HNDABu)2]·9H2O (C1): To a
solution of (NH4)2[Mo3S4Cl6(H2O)3] (0.25 g, 0.32 mmol) in HCl
(2 m solution, 5 mL) was added H3NDABu (0.3 g, 1.4 mmol) dis-
solved in a minimal amount of NaOH (4 m solution). The pH was
adjusted to 1.5 by the addition of NaOH (4 m solution). The solu-
tion was heated at 90 °C for 30 min. Then, the remaining green
precipitate was removed by filtration. CsCl (0.3 g, 1.78 mmol) was
added to the solution. After a few days at 4 °C, green crystals of
Na2Cs[Mo3S4(NDABu)(HNDABu)2]·9H2O (0.2 g, 40%) were iso-
lated. On the TG curve in the temperature range 30–200 °C, the
first weight loss of 12.3% corresponds to the nine lattice water
molecules in C1 (calcd. 11.3%). 1H NMR (400 MHz, [D6]DMSO):
δ = 4.40–4.25 (m, 12 H), 4.03 (d, J = 15.9 Hz, 6 H), 2.32–2.15 (br.
s, 12 H) ppm. H NMR (400 MHz, D2O): δ = 4.74 (s, 6 H), 4.50–
4.60 (br. s, 6 H), 4.25 (d, J = 16.5 Hz, 6 H), 2.35 (s, 12 H) ppm.
IR: ν = 457 (w), 493 (w), 531 (w), 626 (w), 766 (w), 788 (w), 916
(m), 981 (w), 1058 (w), 1086 (w), 1231 (w), 1293 (w), 1631 (C=O,
br. s), 1529 (sh), 1465 (sh), 1390 (br. s) cm–1. C24H50CsMo3N3-
Na2O27S4 (1407.61): calcd. C 20.47, H 3.58, Cs 9.45, Mo 20.48, N
2.98, Na 3.27, S 9.11; found C 21.31, H 3.74, Cs 8.91, Mo 20.39,
N 3.15, Na 3.01, S 10.01.
1
2.50 (br. s, 2 H, NH2) ppm. H NMR (400 MHz, CDCl3): δ = 7.88
(d, J = 8.2 Hz, 2 H), 7.26 (d, J = 8.2 Hz, 2 H), 3.80 (s, 2 H, CH2),
3.78 (s, 3 H, OMe) ppm. 13C NMR (100 MHz, [D6]DMSO): δ =
166.2, 149.8, 129.1, 127.6, 127.2, 51.9, 45.2 ppm. 13C NMR
(100 MHz, CDCl3): δ = 166.6, 148.2, 129.5, 128.3, 126.6, 51.6,
45.8 ppm. HRMS (ESI): calcd. for [M + H]+ 166.0862; found
166.0862.
Methyl 4-{[Bis(2-methoxy-2-oxoethyl)amino]methyl}benzoate (9):
To a solution of 8 (1 g, 6 mmol) in absolute ethanol were success-
ively added 3 (1.13 mL, 12 mmol) and potassium carbonate (1.24 g,
9 mmol), and the reaction mixture was heated at reflux for 24 h.
The solution was filtered to remove the excess amount of K2CO3,
and the solid was washed with diethyl ether. The solution was
transferred back to a round-bottomed flask, and the solvent was
removed under reduced pressure. The resulting oil was purified by
column chromatography (SiO2, CH2Cl2/acetone) to give the triester
(1.71 g, 92%) as a yellow oil. 1H NMR (400 MHz, CDCl3): δ =
3.48 (s, 4 H, NCH2CO2Me), 3.62 (s, 6 H, OCH3), 3.82 (s, 3 H,
OCH3), 3.90 (s, 2 H, PhCH2N), 7.39 (d, J = 8.1 Hz, 2 H), 7.91 (d,
J = 8.1 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 51.3,
51.8, 53.9, 57.4, 128.6, 129.1, 129.5, 143.5, 166.7, 171.2 ppm.
HRMS (ESI): calcd. for [M + H]+ 310.1285; found 310.1285.
1
˜
Synthesis of NaK[Mo3S4(HNDAPr)3]·3.5H2O (C2): To a solution
of (NH4)2[Mo3S4Cl6(H2O)3] (0.5 g, 0.64 mmol) in HCl (2 m solu-
tion, 20 mL) was added H3NDAPr (0.39 g, 1.9 mmol) dissolved in
a minimal amount of NaOH (4 m solution). The pH was adjusted
to 1.5 by the addition of NaOH (4 m solution). The solution was
heated at 90 °C for 30 min. Then, the remaining green precipitate
was removed by filtration. After a few days at room temperature,
Na2[Mo3S4(HNDAPr)3]·8H2O (0.32 g, 41%) was isolated as a
green powder. On the TG curve in the temperature range 30–
190 °C, the first weight loss of 11.9% corresponds to the eight lat-
tice water molecules in Na2[Mo3S4(HNDAPr)3]·8H2O (calcd.
11.05%). 1H NMR (400 MHz, [D6]DMSO): δ = 4.65 (t, J = 6.8 Hz,
6 H), 4.33 (d, J = 15.2 Hz, 6 H), 3.95 (d, J = 15.7 Hz, 6 H), 3.03
4-{[Bis(carboxymethyl)amino]methyl}benzoic Acid (H3NDABn)
(a) Hydrolysis of 9: To a solution of KOH (9 g, 225 mmol) in H2O
(25 mL) and ethanol (25 mL) was added 9 (10 g, 32 mmol), and the
solution was heated at reflux for 48 h. After removal of the vola-
tiles, the remaining aqueous layer was acidified to pH = 5 by the
addition of a diluted aqueous HCl solution. The aqueous phase
was extracted with diethyl ether (3ϫ 100 mL) to remove all of the
organic impurities. The aqueous phase was concentrated to dryness
in a rotary evaporator. To remove the potassium chloride, the white
solid was recrystallized several times from methanol. The title com-
pound (4.10 g, 48%) was obtained as a white solid.
(t, J = 7.1 Hz, 6 H) ppm. IR: ν = 459 (w), 483 (w), 555 (w), 756
˜
(w), 901 (w), 913 (w), 934 (w), 955 (w), 978 (w), 1033 (w), 1091
(w), 1210 (w), 1240 (w), 1249 (w), 1297 (w), 1462 (w), 1716 (C=O,
sh), 1625 (br. s), 1462 (m), 1389 (br. m), 1362 (sh) cm–1.
C21H43Mo3N3Na2O26S4 (1215.61): calcd. C 20.74, H 3.54, Mo
23.68, N 3.46, Na 3.79, S 9.78; found C 20.52, H 3.28, Mo 23.63,
N 3.5, Na 3.14, S 10.06. This powder was recrystallized from a
solution of KCl (0.1 m), and a few crystals of NaK[Mo3S4(HND-
APr)3]·3.5H2O (C2) were isolated for X-ray crystal structure analy-
sis.
(b) Direct Synthesis from 7: Compound 5 (7.36 g, 53 mmol) in H2O
(50 mL) was neutralized by adding KOH (3.24 g, 58 mmol) under
nitrogen at room temperature over a period of 20 min. To this solu-
tion was added 7 (3.93 g, 26 mmol), which was neutralized in H2O
(50 mL) with KOH (1.53 g, 26 mmol). The mixture was heated at
reflux under nitrogen for 5 h, and a solution of KOH (3.14 g,
56 mmol) in water (10 mL) was added over the first 30 min of heat-
ing. The solution was cooled to room temperature, and the pH was
adjusted to 6.5 by the addition of HCl (6 m solution). The solution
was concentrated under vacuum, until a white precipitate of potas-
sium salts appeared. The solid was removed by filtration, and the
pH of the resulting solution was adjusted to 2.5 by the addition of
HCl (6 m solution). The solution was cooled in an ice bath, and
the product precipitated after 30 min. The precipitate was removed
by filtration and dried under vacuum to give H3NDABn (5.91 g,
Synthesis of Li2[Mo3S4(HNDABn)3]·6H2O (C3): To a solution of
(NH4)2[Mo3S4Cl6(H2O)3] (0.2 g, 0.26 mmol) in HCl (2 m solution,
10 mL) was added H3NDABn (0.22 g, 0.82 mmol) dissolved in a
minimal amount of LiOH (1 m solution). The pH was adjusted to
1.2 by the addition of LiOH (1 m solution). The solution was
heated at 90 °C for 30 min. The abundant green precipitate was
removed by filtration and then was washed with EtOH (2ϫ 20 mL)
and dried with Et2O (2ϫ 20 mL) to give C3 (0.19 g, 61%). On the
Eur. J. Inorg. Chem. 2013, 1149–1156
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of 8.5% corresponds to the six lattice water molecules (calcd.
8.57%). IR: ν = 514 (w), 568 (w), 702 (w), 754 (w), 869 (w), 922
˜
(w), 994 (w), 1019 (w), 1115 (w), 1183 (w), 1271 (sh), 1324 (m),
1614 (C=O, br. s), 1385 (br. s) cm–1. C36H45Li2Mo3N3O24S4
(1333.70): calcd. C 32.42, H 3.40, Li 1.04, Mo 21.58, N 3.15, S
9.62; found C 30.52, H 3.28, Li 0.9, Mo 22.63, N 3.5, S 10.06.
HRMS (ESI): calcd. for [M]2– 606.3915; found 606.3914.
Supporting Information (see footnote on the first page of this arti-
cle): FTIR (Figure S1) and TGA curves (Figure S2).
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The authors gratefully acknowledge Andrew Pinkerton who par-
ticipated as Erasmus student for the syntheses presented in this
work. The University of Versailles Saint Quentin en Yvelines and
the Centre National de la Recherche Scientifique (CNRS) are
thanked for their financial support. Dr. Israel Mbomékallé is also
acknowledged for helpful discussions.
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Received: October 16, 2012
Published Online: December 19, 2012
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© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim