КООРДИНАЦИОННАЯ ХИМИЯ, 2012, том 38, № 1, с. 67-72
УДК 541.49
SYNTHESIS AND X-RAY STRUCTURAL CHARACTERIZATION OF DIOXOMOLYBDENUM(VI) COMPLEXES WITH N'-(5-CHLORO-2-HYDROXYBENZYLIDENE)-4-METHYLBENZOHYDRAZIDE AND N'-(2-HYDROXYBENZYLIDENE)-4-METHYLBENZOHYDRAZIDE
© 2012 Y. Lei* and C. Fu
School of Chemistry & Environmental Engineering, Chongqing Three Gorges University, Chongqing 404000, P.R. China
*E-mail: leiyan222@yahoo.cn Received January 13, 2011
Two new dioxomolybdenum(VI) complexes, [MoO2(ClHm)(CH3OH)] (I) and [MoO2(Hm)(CH3OH)] (II) with the hydrazone ligands H2ClHm and H2Hm derived from 4-methylbenzohydrazide with 5-chlorosalicyla-ldehyde and salicylaldehyde, respectively, have been synthesized and structurally characterized by physico-chemical methods and single-crystal X-ray determination. The crystal of I crystallizes in the triclinic space group Pi, with a = 7.839(2), b = 9.656(3), c = 11.548(4) A, a = 88.885(3)°, в = 87.454(3)°, у = 88.996(3)°, V= 873.0(5) A3, Z = 2, R1 = 0.0292, wR2 = 0.0685, S = 1.092. The crystal of II crystallizes in the triclinic space group Pi, with a = 7.780(2), b = 10.584(3), c = 10.628(3) A, a = 91.462(3)°, в = 104.818(3)°, у = 103.288(3)°, V= 820.1(4) A3, Z = 2, Rx = 0.0403, wR2 = 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.
INTRODUCTION
EXPERIMENTAL
The coordination chemistry of molybdenum(VI) has attracted considerable attention due to its biological importance [1—3] and application as catalysts in various oxidations reactions [4—6]. Recent reports indicate that the molybdenum(VI) complexes with hydrazone ligands possess the oxygen atom transfer properties as they were found to oxidize thiols, hydrazine, polyketones, and tertiary phosphines [7, 8]. Moreover, molybdate as a functional mimic for vanadium-halop-eroxidase enzymes shows a higher catalytic activity as compared to vanadate [9]. However, in comparison with the oxovanadium complexes, the number of crystal structures of molybdenum complexes with hydrazone ligands is rather few. Herein, we report the synthesis and crystal structures of two new dioxomolybde-num(VI) complexes, [MoO2(ClHm)(CH3OH)] (I) and [MoO2(hm)(CH3OH)] (II), with similar triden-tate hydrazone ligands N'-(5-chloro-2-hydroxyben-zylidene)-4-methylbenzohydrazide (H2ClHm) and N'-(2-hydroxybenzylidene)-4-methylbenzohydrazide (H2Hm), respectively, as shown below:
X
OH
X = Cl for H2ClHm, X = H for H2Hm.
Materials. Ammonium molybdate, acetylacetone, 5-chlorosalicylaldehyde, salicylaldehyde, and 4-me-thylbenzohydrazide were purchased from Aldrich. [MoO2(Acac)2] was prepared and purified as described previously [10]. All other reagents were used as received without further purification.
Synthesis of H2ClHm. Hot methanol solutions of 5-chlorosalicylaldehyde and 4-methylbenzohydrazide (1 : 1, v/v) were stirred under reflux for 1 h and cooled to room temperature. The precipitate was then filtered, washed with methanol, and dried in vacuo. The yield was 93%.
For C15H13ClN2O2
anal. calcd., %: C, 62.4; H, 4.5; N, 9.7. Found, %: C, 62.2; H, 4.6; N, 9.8.
Synthesis of H2Hm was similar to that of H2ClHm except that salicylaldehyde was used instead of 5-chlo-rosalicylaldehyde. The yield was 91%.
For C15H!4N2O2
anal. calcd., %: C, 70.8;
Found, %: C, 70.5;
H, 5.6; N, 11.0. H, 5.6; N, 11.2.
Synthesis of I. To a stirred solution of H2ClHm (0.29 g, 1 mmol) in 50 ml of methanol was added
67
5*
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 X-ray diffraction were obtained by the recrystallization of the solid from methanol.
For C16H15ClMoN2O5
anal. calcd., %: Found, %:
C, 43.0; C, 43.3;
H, 3.4; H, 3.5;
N, 6.3. N, 6.2.
RESULTS AND DISCUSSION
The two hydrazone compounds are readily prepared by the Schiff base condensation reaction of 4-methylbenzohydrazide with 5-chlrosalicylaldehyde and salicylaldehyde, respectively, in methanol:
O
N 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%.
For Ci6Hi6MoN2O5
anal. calcd., %: C, 46.6; H, 3.9; N, 6.8. Found, %: C, 46.4; H, 3.9; N, 6.7.
Physical measurements. Infrared spectra (4000— 400 cm-1) were recorded as KBr discs with a FTS-40 BioRad FT-IR spectrophotometer. Electronic spectra were recorded on a Shimadzu UV 3101 spectrophotometer. Microanalyses (C, H, and N) of the ligands and the complexes were carried out on a Carlo-Erba 1106 elemental analyzer. Solution electrical conductivity was measured at 298 K using a DDS-11 conductivity meter.
X-ray crystallography. Crystallographic data of complexes I and II were collected on a Bruker SMART CCD area diffractometer with graphite-monochromated Mo^a radiation (X = 0.71073 A) at 298(2) K. Absorption corrections were applied by using the multi-scan program [11]. The structures were solved by direct methods and successive Fourier difference syntheses (SHELXS-97), and anisotropic thermal parameters for all nonhydrogen atoms were refined by a full-matrix least-squares procedure against F2 (SHELXL-97) [12]. All non-hydrogen 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 Fourier map and refined isotropically with O-H distances restrained to 0.85 A. The crystallographic data and experimental details for the structure analysis are summarized in Table 1, and the selected bond lengths and angles are listed in Table 2.
Supplementary material for structure I and II has been deposited with the Cambridge Crystallographic Data Centre (nos. 807009 (I) and 807010 (II); deposit@ccdc. cam.ac.uk or http://www.ccdc.cam.ac.uk).
X
OH
O
X = Cl for H2ClHm, X = H for H2Hm.
The stoichiometric reactions of the hydrazone ligands with MoO2(Acac)2 as a molybdenum source in refluxing methanol yielded the corresponding dioxo-molybdenum(VI) complexes I and II:
X
U
Mo
MeOH O X = Cl for (I), X = H for (II).
The reaction progress is accompanied by an immediate color change of the solution from slight yellow to orange. We have attempted to prepare and grow diffraction quality crystals of the complexes from various solvents; however, only methanol is suitable. The molar conductance values of the complexes measured in absolute methanol at a concentration of 10-3 mol l_1 is 17.2 and 21.5 fi-1 cm2 mol-1, indicating the nonelec-trolytic nature of the complexes in methanol [13].
The perspective views of complexes I and II are shown in Figs. 1 and 2, respectively. The two complexes 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 I and 5.5(1)° for II. The hydrazone ligand coordinates in a dianionic fashion forming five- and six-membered chelate rings with the Mo atom. This is evident from
KOOP^HH^HOHHAtf XHMH3 TOM 38 № 1 2012
Table 1. Crystallographic data and experimental details for complex I and II
Parameters Value
I II
Formula C16H15ClMoN2O5 C16H16MoN2O5
Formula weight 446.7 412.2
Crystal system Triclinic Triclinic
Space group PI PI
a, A 7.839(2) 7.780(2)
b, A 9.656(3) 10.584(3)
c, A 11.548(4) 10.628(3)
a, deg 88.885(3) 91.462(3)
ß, deg 87.454(3) 104.818(3)
Y, deg 88.996(3) 103.288(3)
V, A3 873.0(5) 820.1(4)
Z 2 2
Crystal size, mm 0.27 x 0.27 x 0.23 0.30 x 0.28 x 0.27
Pcalcd g cm-3 1.699 1.669
M-Mo, mm-1 0.933 0.828
Scan mode Multiscan Multiscan
/(000) 448 416
9 Range, deg 2.11-27.00 2.68-26.98
hkl Range -10 < h < 8 -10 < h < 8
-12 < k < 12 -10 < h < 8
-13 < l < 14 -10 < h < 8
Reflections collected 5724 6135
Independent reflections (Rint) 3669 3453
Number of reflections with I > 2ct(I) 3280 2845
Parameters 231 222
Restraints 1 1
Goodness-of-fit on F2 1.092 1.065
R indices (I > 2a(I)) R1 = 0.0292 R1 = 0.0403
wR2 = 0.0685 wR2 = 0.0784
R indices (all data) Rx = 0.0341 Rx = 0.0536
wR2 = 0.0708 wR2 = 0.0833
Largest different peak and hole, e A-3 0.344 and -0.600 0.417 and -0.687
KOOP,3HHAUHOHHAH XHMH3 tom 38 № 1 2012
Table 2. Selected bond (Á) and angles (deg) for I and II
Bond I II
d, Á
Mo(1)—O(1) 1.920(2) 1.921(2)
Mo(1)—O(2) 1.996(2) 2.007(2)
Mo(1)—O(3) 1.690(2) 1.685(3)
Mo(1)—O(4) 1.694(2) 1.693(2)
Mo(1)—O(5) 2.365(2) 2.389(3)
Mo(1)—N(1) 2.249(2) 2.237(3)
Angle Ю, i deg
O(3)Mo(1)O(1) 98.6(1) 98.8(1)
O(4)Mo(1)O(1) 101.4(1) 102.1(1)
O(1)Mo(1)O(2) 150.3(1) 150.0(1)
O(1)Mo(1)N(1) 81.4(1) 81.2(1)
O(1)Mo(1)O(5) 82.4(1) 82.0(1)
O(3)Mo(1)O(2) 96.5(1) 97.1(1)
O(4)Mo(1)O(2) 98.8(1) 97.7(1)
O(2)Mo(1)N(1) 71.4(1) 71.4(1)
O(2)Mo(1)O(5) 78.9(1) 79.0(1)
O(3)Mo(1)O(4) 106.1(1) 106.1(1)
O(3)Mo(1)N(1) 97.0(1) 98.0(1)
O(3)Mo(1)O(5) 171.0(1) 172.1(1)
O(4)Mo(1)N(1) 155.9(1) 154.6(1)
O(4)Mo(1)O(5) 82.4(1) 81.3(1)
N(1)Mo(1)O(5) 74.2(1) 74.2(1)
the N(2)-C(8) and O(2)-(8) bond lengths with values of about 1.305(4) and 1.315(4) A, 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 phe-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 from the least-squares planes of 0.055(2) Á for I and
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