Synthesis, crystal structure, and thermal stability of [Mo 2O4(μ2-O)(C6H4O 2)2(H2O)]·(C8H 9N2)2·2H2O

Article abstract of DOI:10.1134/S1070328414010096

From hydrothermal treatment of benzene-1,2-diamine, pyrocatechol, and MoO₃ in acetic acid solution, a new compound, [Mo₂(μ ₂-O)₂(C₆H₄O₂) ₂(H₂O)]·(C₈H₉N ₂)₂·2H₂O (I), constructed from pyrocatechol chelated dinuclear molybdenum units and 2-methylbenzimidazole has been synthesized. Single-crystal structure analysis reveals that the compound crystallizes in the monoclinic space group P2₁/c with a = 23.365(2), b = 7.2214(5), c = 19.3021(16) β = 97.929(4), V = 3225.6(5), Z = 4, M = 808.46, ρ_c = 1.665 g/cm³, μ(MoK _α) = 0.84 mm^-1, F(000) = 1608, the final R = 0.0622 and wR = 0.1484 for 7385 independent reflections with R _int = 0.0393. Interestingly, an in situ condensation between acetic acid and benzene-1,2-diamine has occurred, and the unexpected 2-methyl-1-H-benzo[d] imidazoles serve as counterions and N-H donors to form stable hydrogen-bond network in the crystal. Furthermore, intermolecular hydrogen bonds are found among the cations, anions and crystalline water molecules. The double nuclear molybdenum units are connected by O-H.O hydrogen bonds with the crystalline water molecules to form one-dimensional chains, and the chains are further joined together by N-H.O to form a quasi-two dimensional structure.

Full text of DOI:10.1134/S1070328414010096

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ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2014, Vol. 40, No. 1, pp. 48–53. © Pleiades Publishing, Ltd., 2014.
Synthesis, Crystal Structure, and Thermal Stability
of [Mo2O4(µ2ꢀO)(C6H4O2)2(H2O)] · (C8H9N2)2 · 2H2O1
X. J. Xu
College of Chemistry and Materials, Yulin Normal University, Yulin, 537000 P.R. China
eꢀmail: xxjhb2011@hotmail.com
Received September 22, 2011
Abstract
solution, a new compound, [Mo2(μ2ꢀO)2(C6H4O2)2(H2O)]
catechol chelated dinuclear molybdenum units and 2ꢀmethylbenzimidazole has been synthesized. Singleꢀ
crystal structure analysis reveals that the compound crystallizes in the monoclinic space group 21/ with
= 23.365(2), = 7.2214(5), = 19.3021(16) = 97.929(4), = 4, = 808.46, ρc
= 3225.6(5) Å3
1.665 g/cm3, ) = 0.84 mm–1
(Mo (000) = 1608, the final = 0.0622 and wR = 0.1484 for 7385 indeꢀ
pendent reflections with int = 0.0393. Interestingly, an in situ condensation between acetic acid and benꢀ
—
From hydrothermal treatment of benzeneꢀ1,2ꢀdiamine, pyrocatechol, and MoO3 in acetic acid
·
(C8H9N2)2 2H2O ( ), constructed from pyroꢀ
·
I
P
c
a
b
μ
c
Å,
β
V
R
,
Z
M
=
K
,
F
α
R
zeneꢀ1,2ꢀdiamine has occurred, and the unexpected 2ꢀmethylꢀ1ꢀHꢀbenzo[d] imidazoles serve as counteriꢀ
ons and N–H donors to form stable hydrogenꢀbond network in the crystal. Furthermore, intermolecular
hydrogen bonds are found among the cations, anions and crystalline water molecules. The double nuclear
molybdenum units are connected by O–H⋅⋅⋅O hydrogen bonds with the crystalline water molecules to form
oneꢀdimensional chains, and the chains are further joined together by N–H⋅⋅⋅O to form a quasiꢀtwo dimenꢀ
sional structure.
DOI: 10.1134/S1070328414010096
1
INTRODUCTION
Here MoO3, catecholate, and oꢀphenylenediamine
were selected as reaction substrates for the preparation
of new molybdenum base hybrid molecular materials
in a hydrothermal process. In the reaction system,
acetic acid was used to modulate the pH values, while
In the past few years, the research on hybrid molecꢀ
ular materials has grown into an attractive subject in
inorganic chemistry for their structural diversity, fasciꢀ
nating properties and potential applications [1–4]. In
oꢀphenylenediamine was designed to be used as strucꢀ
this research field, catecholateꢀcoordinated molybdeꢀ ture directing reagents and counter ions. Interestingly,
2ꢀmethylbenzimidazoles, unexpected species coming
from in situ condensation of ꢀphenylenediamine with
acetic acid were found in the crystal structure. Furꢀ
num compounds, a class of molecular materials, have
aroused much interests for their structure similarity to
the oxoꢀtransfer enzymes and potential applications in
catalysis, DNA cleavage and so on [4–8].
o
thermore, the pyrocatechol controlled the selfꢀconꢀ
2−
MoO4
densation of
into clusters and resulted in the
As far as the molecular structure of catecholate is
concerned, it has several favorable factors in the prepꢀ
aration of hybrid molecular materials. Firstly, the
steric geometry and activity of the center metals can be
modulated by two hydroxyl groups at the ortho posiꢀ
tion via chelated coordination [9]. Secondly, the cateꢀ
cholate molecules can effectively control the selfꢀconꢀ
densation of the anions which are tend to form comꢀ
plex structures, such as atomic clusters [7, 10].
Thirdly, the lone pair electrons in the oxygen atoms of
the hydroxyl groups make it possible to form large
amounts of hydrogen bonds which are favorable for
selective catalysis and separation. Besides, the aroꢀ
matic rings can serve as antenna for photon receiving
and emission in the hybrid molecular materials with
fascinating optical property.
formation of diꢀnuclear molybdenum subunits. Thirdꢀ
ly, there are two kinds of hydrogen bonds as O–H⋅⋅⋅
and N–H⋅⋅⋅O make the subunits orderly organized inꢀ
O
to a quasiꢀ2ꢀdimensional structure.
EXPERIMENTAL
Materials and instruments. All starting materials
were purchased commercially and used as received
without further purification. IR spectrum (KBr pelꢀ
lets) was recorded on a Magna 750 FTꢀIR spectromeꢀ
ter in the range of 400–4000 cm–1. Elemental analysis
was carried out on an Elementar Vario EL III elemenꢀ
tal analyzer. Thermogravimetric analysis (TGA) was
performed on a NETSCHZ STAꢀ449C thermoanaꢀ
lyzer from 30 to 1200
°
C with a heating rate of
1
The article is published in the original.
10°C/min in flowing air.
48

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SYNTHESIS, CRYSTAL STRUCTURE, AND THERMAL STABILITY
49
Table 1. Crystallographic data and experimental details for
complex
Synthesis of [Mo2O4(µ2ꢀO)(C6H4O2)2(H2O)]
(C8H9N2)2 · 2H2O (I). In a typical synthesis, MoO3
·
I
(0.1 g), benzeneꢀ1,2ꢀdiamine (0.1 g), pyrocatechol
(0.1 g), and H2O (13 mL) were mixed in a 23 mL Teꢀ
flonꢀlined stainless steel autoclave. After stirring for a
few minutes, the pH value was modulated to 4.3 with
acetic acid, and then the autoclave was sealed, heated
Parameter
Value
Crystal system
Space group
Monoclinic
to 180
5 days. After the reactor was cooled down to room
temperature at a rate of 5 C/h, redꢀbrown crystals
°
C, and maintained at the temperature for
P
21/c
°
a,
b,
c,
Å
Å
Å
23.365(2)
7.2214(5)
19.3021(16)
90.00
suitable for Xꢀray structure analysis were separated by
filtration and dried naturally (86% yield based on moꢀ
lybdenum).
For C28H32N4O12Mo2 (I)
anal. calcd., %:
Found, %:
C, 41.25;
C, 41.66;
H, 4.02;
H, 3.97;
N, 6.77.
N, 6.94.
α
, deg
, deg
, deg
β
97.929(4)
90.00
IR (
, cm–1): 3426 m, 3060 w, 1629 m, 1575 m, 1477 s,
1257 s, 1104 w, 1020 w, 905 s, 814 s, 738 s, 624 s.
ν
γ
Xꢀray structure determination. A red brown single
V, Å3
3225.6(5)
4
crystal with dimensions of 0.32
×
0.29 0.06 mm was seꢀ
×
lected and mounted on a glass fiber for structure determiꢀ
nation. Xꢀray diffraction data were collected on a Bruker
Smart CCD diffractometer equipped with graphiteꢀ
Z
ρcalcd, g cm–3
Crystal size, mm
1.665
monochromated Mo
K
radiation (
λ
= 0.71073
Å) in the
α
range of 3.02° ≤ θ ≤ 27.48
°
at 293 K. An empirical abꢀ
0.32
×
0.29
1632
0.84
×
0.06
sorption correction was applied using the SADABS proꢀ
gram [11]. The crystal structure was solved by direct
methods with SHELXSꢀ97 program [12], and refined
by fullꢀmatrix leastꢀsquares techniques on F2 with
SHELXLꢀ97 software package [13]. All nonꢀhydrogen
atoms were rened anisotropically. The position of the hyꢀ
drogen atoms were generated geometrically, rened with
isotropic thermal parameters, and allowed to ride on their
F
μ
θ
(000)
(Mo
K
), mm–1
α
Range for data collection, deg
3.02 to 27.48
23, –9
Index range
Type of scan
h
,
k,
l
–30
≤
h
–25
≤
≤
k ≤ 9,
parent atoms before the final cycle of refinement. For I, the
≤
l
≤
25
2
2
final
(0.0697
on 6419 reflections with
max = 0.001.
A summary of the crystallographic data and strucꢀ
R
= 0.0622, wR = 0.1484 (
)2 + 7.0167
], where
> 2
w
= 1/[
σ
+
(Fo )
(Fo2 2Fc ) 3)
), = 1.081 and
2
ω
scans
P
P
P
=
+
S
based
I
σ
(I
Reflections collected
24100
(
Δ
/ )
σ
Independent reflections (Rint
)
7385 (0.0393)
6419
ture refinement is shown in Table 1, the selected bond
distances and bond angles are listed in Table 2, and the
hydrogen bond lengths and bond angles are given in
Table 3.
Reflections with
I
> 2σ(I)
Number of parameters
415
Supplementary material for structure
I has been
deposited with the Cambridge Crystallographic Data
Centre (no. 819677; deposit@ccdc.cam.ac.uk or
http://www.ccdc.cam.ac.uk).
Goodnessꢀofꢀfit on F2
1.081
Final R1
,
wR2
(
I
> 2σ(
I
))*
R
R
1 = 0.0622, wR2 = 0.1484
1 = 0.0745, wR2 = 0.1575
0.889 and –0.658
RESULTS AND DISCUSSION
R1
,
wR2 (all data)**
Å–3
The crystal structure of I is built up of pyrocatechol
Δρmax and Δρmin, e
coordinated diꢀnuclear molybdenum anions, protoꢀ
nated 2ꢀmethylbenzimidazole cations, and lattice waꢀ
ter molecules (Fig. 1). In terms of the anions, both of
the metal atoms are in octahedral geometry. The
*
R
=
Σ
(F
–
F
)/
Σ
(F
), ** wR = { [w –
(Fo2
F 2)2] (F 2)2}1 2
.
c o
Σ
∑
o
c
o
2
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50
XU
Table 2. Selected bond lengths (Å) and bond angles (deg) for complex
I
Bond
d
, Å
Bond
d
, Å
Bond
d, Å
Mo(1)–O(4)
Mo(1)–O(5)
Mo(1)–O(3)
Mo(1)–O(9))
1.694(4)
1.728(4)
1.948(3)
1.975(4)
Mo(1)–O(8)
Mo(1)–O(7)
Mo(2)–O(2)
Mo(2)–O(1)
2.140(3)
2.329(3)
1.705(4)
1.714(4)
Mo(2)–O(3)
Mo(2)–O(6)
Mo(2)–O(7)
Mo(2)–O(10)
1.930(3)
1.961(4)
2.116(3)
2.506(4)
Angle
ω
, deg
Angle
ω
, deg
Angle
ω
, deg
O(4)Mo(1)O(5)
O(4)Mo(1)O(3)
O(5)Mo(1)O(3)
O(4)Mo(1)O(9)
O(5)Mo(1)O(9)
O(3)Mo(1)O(9)
O(4)Mo(1)O(8)
O(5)Mo(1)O(8)
O(3)Mo(1)O(8)
O(9)Mo(1)O(8)
102.11(18)
97.61(17)
102.78(17)
102.53(18)
92.51(17)
151.53(15)
94.11(17)
161.86(16)
82.81(14)
75.92(15)
O(4)Mo(1)O(7)
O(5)Mo(1)O(7)
O(3)Mo(1)O(7)
O(9)Mo(1)O(7)
O(8)Mo(1)O(7)
O(2)Mo(2)O(1)
O(2)Mo(2)O(3)
O(1)Mo(2)O(3)
O(2)Mo(2)O(6)
O(1)Mo(2)O(6)
166.16(16)
86.47(15)
69.67(12)
87.74(14)
79.27(13)
104.3(2)
O(3)Mo(2)O(6)
O(2)Mo(2)O(7)
O(1)Mo(2)O(7)
O(3)Mo(2)O(7)
O(6)Mo(2)O(7)
O(2)Mo(2)O(10)
O(1)Mo(2)O(10)
O(3)Mo(2)O(10)
O(6)Mo(2)O(10)
O(7)Mo(2)O(10)
148.03(15)
101.69(17)
153.97(18)
74.83(13)
76.07(14)
175.15(17)
80.51(17)
79.50(13)
79.82(13)
73.53(13)
98.60(18)
102.65(17)
99.99(18)
97.67(18)
Table 3. Geometric parameters of hydrogen bonds for I*
Mo(1) atom is coordinated by six oxygen atoms,
including two terminal oxygen atoms (O(4), O(5)),
O(8) and O(9) atoms provided by a pyrocatechol, O(7)
atom from another pyrocatechol, and O(3) sharing
with the Mo(2) atom. The Mo(2) atom is also coordiꢀ
nated by six oxygen atoms, including O(1) and O(2) as
terminal atoms, O(6) and O(7) from the pyrocatechol,
O(3) sharing with the Mo(1) atom, and an oxygen
O(10) provided by the coordinated water. The two
MoO6 octahedrons are sharing a common edge conꢀ
structed by O(7) from a pyrocatechol and μ2ꢀO(3).
Distance, Å
Angle
DHA,
deg
Contact D–H⋅⋅⋅
A
D–H H···A D···A
O(1
O(1
O(2
O(2
w
w
w
w
)
)
)
)
−
−
−
−
H(1wA)···O(5)a 0.96
1.96 2.904(5) 168
H(1wB)···O(8)b 0.96 1.85 2.798(5) 168
H(2wA)···O(1)c 0.96 1.83 2.789(7) 179
H(2wB)···O(2)d 0.96
H(10
)···O(5)e 0.85 2.02 2.764(5) 146
1.94 2.898(7) 179
Apart from static electronic interactions among the
anions and cations, abundant hydrogen bonds are
found to link the subunits from different directions. As
listed in Table 2, there are two kinds of hydrogen bonds
as O–H⋅⋅⋅O and N–H⋅⋅⋅O that make the subunits orꢀ
derly organized. Typical O–H⋅⋅⋅O hydrogen bonds are
shown in Fig. 2 and the H atoms are omitted for clarity.
O(10)
−
B
N(1)
N(2)
N(3)
N(4)
−
H(1
H(2
H(3
H(4
B
B
B
)···O(2
)···O(3)
)···O(1
w
)
0.86
0.86
0.86
1.92 2.746(7) 161
1.90 2.751(5) 169
1.94 2.769(6) 161
−
−
−
Firstly, the lattice water molecules marked as O(2w)
w
)
are serving as double hydrogen donors to form hydroꢀ
gen bonds with terminal oxygen atoms O(5) and O(8)
from neighboring anions. Secondly, another kind of
A)···O(10)
0.86 2.00 2.797(6) 154
* Symmetry transformations used to generate the equivalent atoms:
lattice water molecules marked as O(1
ving as double hydrogen donors to form hydrogen
bonds with O(3) donated by the catechol molecules
w) are also serꢀ
a
b
c
x
z
, –
+ 1;
y
+ 3/2,
z
+ 1/2;
x
, –
z
y
+ 1;
+ 1/2,
z
y
+ 1/2;
– 1, z.
–x + 1, –y + 1,
d
e
–
–x
+ 1, – + 2, –
y
x,
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SYNTHESIS, CRYSTAL STRUCTURE, AND THERMAL STABILITY
O(1
51
w
)
O(4)
O(5)
Mo(1)
O(9)
O(8)
O(2w)
O(7)
O(3)
N(2)
O(2)
O(10)
N(1)
N(4)
Mo(2)
O(6)
O(1)
N(3)
Fig. 1. Molecular structure of compound I.
O(2w)
y
z
O(2)
Mo(2)
O(1)
x
O(5)
O(10)
Mo(1)
O(1
w)
O(8)
C
C
C
C
Fig. 2. Oneꢀdimensional assembly of the catecholꢀMo subunits via O–H⋅⋅⋅O hydrogen bonds.
and terminal oxygen atoms O(5) from neighboring anꢀ dimensional array of the separated subunits connected
ions. Furthermore, the H2O molecules coordinate to by N–H⋅⋅⋅O hydrogen bonds is presented in Fig. 4.
the Mo(2) atoms marked as O(10) also donate hydroꢀ
gen atoms to form O–H⋅⋅⋅O hydrogen bonds with the
terminal oxygen atoms marked as O(5) from neighboꢀ
ring anions. These three types of O–H⋅⋅⋅O hydrogen
bonds make pyrocatechol coordinated dinuclear moꢀ
lybdenum anions orderly aligned along the
(010) direction.
Notably, there are no 2ꢀmethylbenzimidazoles but
ꢀphenylenediamines were used as substrates in the
preparation of compound . The appearance of 2ꢀmeꢀ
thylbenzimidazoles in the products indicates an in situ
reaction occurred in the hydrothermal procedure. The
unexpected species may originate from the condensaꢀ
o
I
tion between the oꢀphenylenediamine and the acetic
acid under autogenous pressure at 180°C:
In terms of the O–H⋅⋅⋅O hydrogen bonds, the two
pronated 2ꢀmethylbenzimidazole cations are both serꢀ
ve as double hydrogen bonds donors in the crystal
structure with N⋅⋅⋅O distances ranging from 2.746(7)
NH2
N
OH
6+
Mo
+
CH3
H3C
180°C
O
NH2
N
H
to 2.797(6)
2ꢀmethylbenzimidazoles are connecting with lattice
water molecules (marked as O(2 )), while the N(2)
Å. As show in Fig. 3a, the N(1) atoms of
w
Once the reaction was carried out in absent of
molybdenum, no crystals can be found. In previous reꢀ
ports, such condensation usually occurred in presence
of polyphosphoric acid. The polyphosphoric acid can
effectively promote the condensation reaction by reꢀ
atoms are linked with the μ2ꢀO(3) atoms. However, in
Fig. 3b the nitrogen atoms of the 2ꢀmethylbenzimidaꢀ
zole are connected with one lattice water (O(1w)) and
the coordinated H2O molecules (O(10)). A quasiꢀtwo
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2014