Synthesis and X-ray structural characterization of dioxomolybdenum(VI) complexes with N'-(5-chloro-2-hydroxybenzylidene)-4-methylbenzohydrazide and N'(2-hydroxybenzylidene)-4-methylbenzohydrazide

Article abstract of DOI:10.1134/S1070328411120037

Two new dioxomolybdenum(VI) complexes, [MoO₂(ClHm)(CH ₃OH)] (I) and [MoO₂(Hm)(CH₃OH)] (II) with the hydrazone ligands H₂ClHm and H₂Hm derived from 4-methylbenzohy-drazide with 5-chlorosalicylaldehyde and salicylaldehyde, respectively, have been synthesized and structurally characterized by physicochemical methods and single-crystal X-ray determination. The crystal of I crystallizes in the triclinic space group $Πbar 1$$, with a = 7.839(2), b = 9.656(3), c = 11.548(4) A α = 88.885(3)°, β = 87.454(3)°, γ = 88.996(3)°, V = 873.0(5) A³, Z = 2, R ₁ = 0.0292, wR ₂ = 0.0685, S = 1.092. The crystal of II crystallizes in the triclinic space group $Πbar 1$$, with a = 7.780(2), b = 10.584(3), c = 10.628(3) A, α = 91.462(3)°, β = 104.818(3)°, γ = 103.288(3)°, V = 820.1(4) A³, Z = 2, R ₁ = 0.0403, wR ₂ = 0.0784, S = 1.065. An X-ray analysis indicates that the structures of both complexes are similar to each other. The molybdenum atom in each complex is in an octahedral coordination environment constructed by two oxo groups, an NO₂ donor set of the hydrazone ligand, and one methanol O atom.

Full text of DOI:10.1134/S1070328411120037

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2012, Vol. 38, No. 1, pp. 65–70. © Pleiades Publishing, Ltd., 2012.
Synthesis and XꢀRay Structural Characterization
of Dioxomolybdenum(VI) Complexes
with N'ꢀ(5ꢀchloroꢀ2ꢀhydroxybenzylidene)ꢀ4ꢀmethylbenzohydrazide
and N'ꢀ(2ꢀhydroxybenzylidene)ꢀ4ꢀmethylbenzohydrazide1
Y. Lei* and C. Fu
School of Chemistry and Environmental Engineering, Chongqing Three Gorges University, Chongqing 404000, P.R. China
*eꢀmail: leiyan222@yahoo.cn
Received January 13, 2011
Abstract
[MoO2(Hm)(CH3OH)] (II) with the hydrazone ligands H2ClHm and H2Hm derived from 4ꢀmethylbenzohyꢀ
drazide with 5ꢀchlorosalicylaldehyde and salicylaldehyde, respectively, have been synthesized and structurally
characterized by physicochemical methods and singleꢀcrystal Xꢀray determination. The crystal of crystallizes
in the triclinic space group with = 7.839(2), = 9.656(3), = 11.548(4) = 88.885(3) = 87.454(3)
= 2, 1 = 0.0292, wR2 = 0.0685, = 1.092. The crystal of II crystallizes in
= 7.780(2), = 10.584(3), = 10.628(3) = 91.462(3) = 104.818(3)
= 2, 1 = 0.0403, wR2 = 0.0784, = 1.065. An Xꢀray analysis indicates that
—Two new dioxomolybdenum(VI) complexes, [MoO2(ClHm)(CH3OH)]
(I)
and
I
a
b
c
Å
,
α
°
,
β
°
,
P1,
= 873.0(5) Å3
the triclinic space group with
γ
= 88.996(3)
°,
V
,
Z
a
Z
R
S
b
c
Å,
α
°
,
β
°,
P1,
γ
= 103.288(3)
°,
V
= 820.1(4) Å3
,
R
S
the structures of both complexes are similar to each other. The molybdenum atom in each complex is in an octaꢀ
hedral coordination environment constructed by two oxo groups, an NO2 donor set of the hydrazone ligand, and
one methanol O atom.
DOI: 10.1134/S1070328411120037
1
INTRODUCTION
The coordination chemistry of molybdenum(VI)
H
X
N
N
has attracted considerable attention due to its biologiꢀ
cal importance [1–3] and application as catalysts in
various oxidations reactions [4–6]. Recent reports inꢀ
dicate that the molybdenum(VI) complexes with hyꢀ
drazone ligands possess the oxygen atom transfer propꢀ
erties as they were found to oxidize thiols, hydrazine,
polyketones, and tertiary phosphines [7, 8]. Moreover,
molybdate as a functional mimic for vanadium–halopꢀ
eroxidase enzymes shows a higher catalytic activity as
compared to vanadate [9]. However, in comparison
with the oxovanadium complexes, the number of crysꢀ
tal structures of molybdenum complexes with hydraꢀ
zone ligands is rather few. Herein, we report the syntheꢀ
sis and crystal structures of two new dioxomolybdeꢀ
O
OH
X = Cl for H2ClHm, X = H for H2Hm.
EXPERIMENTAL
Materials. Ammonium molybdate, acetylacetone,
5ꢀchlorosalicylaldehyde, salicylaldehyde, and 4ꢀmeꢀ
thylbenzohydrazide were purchased from Aldrich.
[MoO2(Acac)2] was prepared and purified as described
previously [10]. All other reagents were used as reꢀ
ceived without further purification.
Synthesis of H2ClHm. Hot methanol solutions of
5ꢀchlorosalicylaldehyde and 4ꢀmethylbenzohydrazide
(1 : 1, v/v) were stirred under reflux for 1 h and cooled
to room temperature. The precipitate was then filꢀ
tered, washed with methanol, and dried in vacuo. The
yield was 93%.
num(VI) complexes, [MoO2(ClHm)(CH3OH)] (
and [MoO2(hm)(CH3OH)] (II), with similar tridenꢀ
tate hydrazone ligands N ꢀ(5ꢀchloroꢀ2ꢀhydroxybenꢀ
I)
'
zylidene)ꢀ4ꢀmethylbenzohydrazide (H2ClHm) and
N'ꢀ(2ꢀhydroxybenzylidene)ꢀ4ꢀmethylbenzohydrazide
For C15H13ClN2O2
(H2Hm), respectively, as shown below:
anal. calcd., %:
Found, %:
C, 62.4;
C, 62.2;
H, 4.5;
H, 4.6;
N, 9.7.
N, 9.8.
1
The article is published in the original.
65

66
LEI, FU
Synthesis of H2Hm was similar to that of H2ClHm restrained to 0.85 Å. The crystallographic data and exꢀ
perimental details for the structure analysis are sumꢀ
marized in Table 1, and the selected bond lengths and
angles are listed in Table 2.
except that salicylaldehyde was used instead of 5ꢀchloꢀ
rosalicylaldehyde. The yield was 91%.
For C15H14N2O2
Supplementary material for structure
been deposited with the Cambridge Crystallographic
I and II has
anal. calcd., %:
Found, %:
C, 70.8;
C, 70.5;
H, 5.6;
H, 5.6;
N, 11.0.
N, 11.2.
Data Centre (nos. 807009 (
I
) and 807010 (II);
deposit@ccdc.cam.ac.uk
cam.ac.uk).
or
http://www.ccdc.
Synthesis of I. To a stirred solution of H2ClHm
(0.29 g, 1 mmol) in 50 ml of methanol was added
MoO2(Acac)2 (0.33 g, 1 mmol). The resulting mixture
was refluxed for 1 h. The orange reaction solution was
filtered, and the solvent was removed under reduced
pressure, yielding a red solid of the complex. The yield
was 87%. Red single crystals suitable for Xꢀray diffracꢀ
tion were obtained by the recrystallization of the solid
from methanol.
RESULTS AND DISCUSSION
The two hydrazone compounds are readily preꢀ
pared by the Schiff base condensation reaction of
4ꢀmethylbenzohydrazide with 5ꢀchlrosalicylaldehyde
and salicylaldehyde, respectively, in methanol:
O
X
CHO
OH
NH2
For C16H15ClMoN2O5
N
+
H
anal. calcd., %: C, 43.0;
Found, %: C, 43.3;
H, 3.4;
H, 3.5;
N, 6.3.
N, 6.2.
H
Synthesis of II and its crystallization were similar to
that of I except that H2Hm (0.25 g, 1 mmol) was used
instead of H2ClHm. The yield was 83%.
X
N
N
O
OH
X = Cl for H2ClHm, X = H for H2Hm.
For C16H16MoN2O5
anal. calcd., %:
Found, %:
C, 46.6;
C, 46.4;
H, 3.9;
H, 3.9;
N, 6.8.
N, 6.7.
The stoichiometric reactions of the hydrazone
ligands with MoO2(Acac)2 as a molybdenum source in
refluxing methanol yielded the corresponding dioxoꢀ
Physical measurements. Infrared spectra (4000–
400 cm–1) were recorded as KBr discs with a FTSꢀ40
BioRad FTꢀIR spectrophotometer. Electronic spectra
were recorded on a Shimadzu UV 3101 spectrophoꢀ
tometer. Microanalyses (C, H, and N) of the ligands
and the complexes were carried out on a CarloꢀErba
1106 elemental analyzer. Solution electrical conducꢀ
tivity was measured at 298 K using a DDSꢀ11 conducꢀ
tivity meter.
molybdenum(VI) complexes I and II:
H
X
N
N
+ MoO2(Acac)2
O
OH
Xꢀray crystallography. Crystallographic data of
complexes
SMART CCD area diffractometer with graphiteꢀ
monochromated Mo radiation ( = 0.71073 ) at
I and II were collected on a Bruker
X
N
O
N
K
λ
Å
O
α
O
Mo
298(2) K. Absorption corrections were applied by usꢀ
ing the multiꢀscan program [11]. The structures were
solved by direct methods and successive Fourier differꢀ
ence syntheses (SHELXSꢀ97), and anisotropic therꢀ
mal parameters for all nonhydrogen atoms were reꢀ
fined by a fullꢀmatrix leastꢀsquares procedure against
O
MeOH
I), X = H for (II).
X = Cl for (
The reaction progress is accompanied by an immeꢀ
diate color change of the solution from slight yellow to
orange. We have attempted to prepare and grow difꢀ
fraction quality crystals of the complexes from various
solvents; however, only methanol is suitable. The moꢀ
F
2 (SHELXLꢀ97) [12]. All nonꢀhydrogen atoms were
refined anisotropically. Hydrogen atoms were set in
the calculated positions and refined by a riding model
with a common thermal parameter. H atoms for the
methanol molecules were located in difference Fouriꢀ
lar conductance values of the complexes measured in
er map and refined isotropically with O–H distances absolute methanol at a concentration of 10–3 mol l⎯ is
1
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SYNTHESIS AND XꢀRAY STRUCTURAL CHARACTERIZATION
67
Table 1. Crystallographic data and experimental details for complex
I
and II
Value
Parameters
I
II
Formula
C16H15ClMoN2O5
C16H16MoN2O5
412.2
Formula weight
Crystal system
446.7
Triclinic
Triclinic
Space group
P
1
P1
a
, Å
, Å
7.839(2)
9.656(3)
11.548(4)
88.885(3)
87.454(3)
88.996(3)
873.0(5)
2
7.780(2)
10.584(3)
10.628(3)
91.462(3)
104.818(3)
103.288(3)
820.1(4)
2
b
c
, Å
, deg
, deg
, deg
α
β
γ
V
Z
, Å3
Crystal size, mm
ρcalcd, g cm–3
μMo, mm–1
0.27
×
0.27 × 0.23
0.30 × 0.28 × 0.27
1.669
1.699
0.933
0.828
Scan mode
Multiscan
448
Multiscan
416
F(000)
θ
Range, deg
2.11–27.00
2.68–26.98
hkl Range
–10
–12
–13
≤
≤
≤
h
k
l
≤
8
12
–10
–10
–10
≤
≤
≤
h
h
h
≤
≤
≤
8
8
8
≤
≤
14
Reflections collected
5724
3669
3280
231
1
6135
3453
2845
222
1
Independent reflections (Rint
)
Number of reflections with
Parameters
I
> 2σ(I)
Restraints
Goodnessꢀofꢀfit on F2
1.092
1.065
R
indices (
I
> 2
σ
(
I
))
R
1 = 0.0292
R1 = 0.0403
wR2 = 0.0685
wR2 = 0.0784
1 = 0.0536
R
indices (all data)
R
1 = 0.0341
R
wR2 = 0.0708
wR2 = 0.0833
Largest different peak and hole,
e
Å–3
0.344 and –0.600
0.417 and –0.687
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
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68
LEI, FU
Table 2. Selected bond (Å) and angles (deg) for I and II
es are very similar to each other. The hydrazone ligand
in each complex is nearly planar with a dihedral angle
between the two benzene rings of 6.2(1) for and
5.5(1) for II. The hydrazone ligand coordinates in a
I
II
°
I
Bond
d
, Å
°
dianionic fashion forming fiveꢀ and sixꢀmembered
chelate rings with the Mo atom. This is evident from
the N(2)–C(8) and O(2)–(8) bond lengths with values
Mo(1)–O(1)
Mo(1)–O(2)
Mo(1)–O(3)
Mo(1)–O(4)
Mo(1)–O(5)
Mo(1)–N(1)
1.920(2)
1.996(2)
1.690(2)
1.694(2)
2.365(2)
2.249(2)
1.921(2)
2.007(2)
1.685(3)
1.693(2)
2.389(3)
2.237(3)
of about 1.305(4) and 1.315(4) Å, respectively, which
are indicative of the presence of the enolate form of the
ligand amide groups. The coordination around the Mo
atom in each of the complexes is distorted octahedral.
The hydrazone ligand coordinates through one pheꢀ
nolate O, one imine N, and one ethanolic O atoms to
the MoO2 moiety, and the sixth weaker coordination
comes from the O atom of the methanol molecule.
The equatorial donor atoms O(1), O(2), O(4), and
N(1) form a high degree of planarity mean deviations
Angle
ω
, deg
O(3)Mo(1)O(1)
O(4)Mo(1)O(1)
O(1)Mo(1)O(2)
O(1)Mo(1)N(1)
O(1)Mo(1)O(5)
O(3)Mo(1)O(2)
O(4)Mo(1)O(2)
O(2)Mo(1)N(1)
O(2)Mo(1)O(5)
O(3)Mo(1)O(4)
O(3)Mo(1)N(1)
O(3)Mo(1)O(5)
O(4)Mo(1)N(1)
O(4)Mo(1)O(5)
N(1)Mo(1)O(5)
98.6(1)
101.4(1)
150.3(1)
81.4(1)
82.4(1)
96.5(1)
98.8(1)
71.4(1)
78.9(1)
106.1(1)
97.0(1)
171.0(1)
155.9(1)
82.4(1)
74.2(1)
98.8(1)
102.1(1)
150.0(1)
81.2(1)
82.0(1)
97.1(1)
97.7(1)
71.4(1)
79.0(1)
106.1(1)
98.0(1)
172.1(1)
154.6(1)
81.3(1)
74.2(1)
from the leastꢀsquares planes of 0.055(2)
Å
for
for II. The Mo atoms are displaced by
for and 0.347(2) for II toward the axial
I and
0.058(2)
0.334(2)
Å
Å
I
Å
oxo O atoms from the leastꢀsquares planes defined by
the equatorial donor atoms. The Mo–O and Mo–N
bonds in both structures are comparable to each other.
The Mo=O bond lengths are within the previously reꢀ
ported ranges [4, 7, 14]. The rather long Mo–Omethanol
bonds and consequently weak bonding are due to the
trans influence of the oxo groups. The distortion of the
octahedral coordination of both structures can also be
observed from the bond angles related to the Mo atꢀ
oms. The N(1)Mo(1)O(2) bond angles are much less
than ideal values of 90° as a result of the strain created
by the fiveꢀmembered chelate rings Mo(1)–N(1)–
N(2)–C(8)–O(2).
17.2 and 21.5
Ω
–1 cm2 mol–1, indicating the nonelecꢀ
trolytic nature of the complexes in methanol [13].
In the crystal structures of complexes I and II, the
The perspective views of complexes and II are
I
shown in Figs. 1 and 2, respectively. The two complexꢀ molecules are linked via intermolecular O–H⋅⋅⋅N hyꢀ
Cl(1)
C(5)
C(11)
C(10)
C(9)
C(6)
N(2)
C(8)
C(12)
C(13)
C(7)
C(4)
C(3)
C(15)
C(1)
O(3)
N(1)
C(2)
O(1)
C(14)
O(2)
O(5)
Mo(1)
O(4)
C(16)
Fig. 1. ORTEP diagram of complex
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
I
(30% thermal ellipsoid).
No. 1
2012

SYNTHESIS AND XꢀRAY STRUCTURAL CHARACTERIZATION
69
C(5)
C(6)
C(11)
C(7)
N(2)
C(4)
C(10)
C(12)
C(15)
C(8)
C(1)
N(1)
O(3)
C(9)
C(3)
C(2)
C(13)
O(2)
C(14)
O(1)
Mo(1)
O(5)
O(4)
C(16)
Fig. 2. ORTEP diagram of complex II (30% thermal ellipsoid).
x
z
0
y
Fig. 3. Dimeric structures of complex I linked by the O–H⋅⋅⋅N hydrogen bonds.
drogen bonds to form dimers, as shown in Figs. 3 and 4, dioxomolybdenum(VI) moieties. The bands due to
respectively.
ν
(C=O) and (NH) were absent in the complexes,
ν
and new C–O stretches appear at 1270 cm–1. This sugꢀ
gests the occurrence of keto–imine tautomerization of
the hydrazone ligands during the coordination. The
strong bands indicative of the C=N–N=C groups in
The weak bands centered at about 3330 cm–1 in the
IR spectra of both complexes may be attributed to the
(OH) vibrations of the coordinated methanol moleꢀ
cules. The hydrazone ligands show stretching bands
attributed to C=O, C=N, C–OH, and NH at about
1669, 1637, 1155, 1223, and 3278 cm–1, respectively.
The Mo=O stretching modes occur as a pair of sharp
strong bands at 938 and 912 cm–1, assigned to the anꢀ
ν
the two complexes are shifted to 1603 cm–1 for
1602 cm–1 for II. The
(C=N) band appear at
I and
ν
1623 cm–1 in both complexes. The three new peaks
observed at about 815, 721, and 683 cm–1 may be atꢀ
tisymmetric and symmetric stretching modes of the tributed to the Mo–O bonds in the complexes. The
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
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70
LEI, FU
z
0
y
x
Fig. 4. Dimeric structures of complex II linked by the O–H⋅⋅⋅N hydrogen bonds.
3. Katsaros, N., Katsarou, M., Sovilj, S.P., et al., Bioinorg.
Chem. Appl., 2004, vol. 2, no. 3–4, p. 193.
4. Rao, S.N., Munshi, K.N., Rao, N.N., et al., Polyheꢀ
dron, 1999, vol. 18, no. 19, p. 2491.
comparison of the IR spectra of the free ligands and
the dioxomolybdenum(VI) complexes confirms the
enolate coordination mode of the hydrazone ligands.
The electronic spectra for the complexes recorded
in absolute methanol displayed absorption maxima in
the ranges 396–410, 306–312, and 260–267 nm. The
bands at 306–308 and 260–263 nm can be attributed
to the internal ligand transitions. The absorption maxꢀ
ima at 396–410 nm could be assigned to the ligandꢀtoꢀ
5. Mancka, M. and Plass, W., Inorg. Chem. Commun.
2007, vol. 10, no. 6, p. 677.
6. Gharah, N., Chattopadhyay, B., Maiti, S.K., et al.,
Transition Met. Chem., 2010, vol. 35, no. 5, p. 531.
7. Debel, R., Buchholz, A., and Plass, W., Z. Anorg. Allg.
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,
metal Mo(
d
π
)
O(π) chargeꢀtransfer (LMCT)
8. Dinda, R., Sengupta, P., Ghosh, S., et al., Eur. J. Inorg.
Chem., 2003, no. 2, p. 363.
9. Meister, G.E. and Butler, A., Inorg. Chem., 1994,
transition. This is in the range usually observed for the
MoO2 complexes [15].
vol. 33, no. 15, p. 3269.
10. Chen, G.J.J., McDonald, J.W., and Newton, W.E.,
Inorg. Chem., 1976, vol. 15, no. 11, p. 2612.
ACKNOWLEDGMENTS
11. Blessing, R.H., Acta Crystallogr., A, 1995, vol. 51, no. 1,
p. 33.
12. Sheldrick, G.M., SHELXTLꢀ97, Program for Refining
We acknowledge the financial support from the
Chongqing Three Gorges University.
Crystal Structure Refinement, G
Univ. of G ttingen, 1997.
13. Geary, W.J., Coord. Chem. Rev., 1971, vol. 7, no. 1, p. 81.
14. Dinda, R., Ghosh, S., Falvello, L.R., et al., Polyhedron
2006, vol. 25, no. 12, p. 2375.
öttingen (Germany):
ö
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RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
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2012