КООРДИНАЦИОННАЯ ХИМИЯ, 2014, том 40, № 2, с. 87-91
УДК 541.49
TWO MONONUCLEAR MOLYBDENUM(VI) OXO COMPLEXES WITH TRIDENTATE HYDRAZONE LIGANDS: SYNTHESIS AND CRYSTAL STRUCTURES
© 2014 S. S. Qian1, Y. N. Wang2, M. M. Zhen2, Y. N. Li2, D. Huang2, Z. L. You2, *, and H. L. Zhu1, *
1School of Life Sciences, Shandong University of Technology, ZiBo, 255049 P.R. China 2Department of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, 116029 P.R. China *E-mail: hailiang_zhu@163.com;youzhonglu@lnnu.edu.cn Received August 28, 2012
Reaction of [MoO2(Acac)2] (Acac = acetylacetonate) with two similar hydrazone ligands in methanol yielded two mononuclear molybdenum(VI) oxocomplexes with general formula [MoO2(L)(CH3OH)], where L = = L1 = (4-nitrophenoxy)acetic acid [1-(3-ethoxy-2-hydroxyphenyl)methylidene]hydrazide (H2L1) and L = = L2 = (4-nitrophenoxy)acetic acid [1-(5-bromo-2-hydroxyphenyl)methylidene]hydrazide (H2L2). Crystal and molecular structures of the complexes were determined by single crystal X-ray diffraction method. All investigated compounds were further characterized by elemental analysis and FT-IR spectra. Single crystal X-ray structural studies indicate that the hydrazone ligands coordinate to the MoO2 cores through enolate oxygen, phenolate oxygen, and azomethine nitrogen. The Mo atoms in both complexes are in octahedral coordination.
DOI: 10.7868/S0132344X14020078
INTRODUCTION
The coordination chemistry of molybdenum(VI) has attracted considerable attention due to its recently discovered biochemical significance [1—3] as well as for the efficient catalytic properties in several organic synthesis procedures [4—7]. In recent years, a great number of molybdenum(Vl) complexes with Schiff bases derived from salicylaldehyde and primary amines have been reported [8—10]. Hydrazones, bearing —C(O)—NH—N=CH— groups, are a kind of special Schiff bases, which are of particular interest in co-
ordination chemistry and biological applications. However, molybdenum(VI) complexes derived from hydrazone ligands have seldom been reported. In the present work, we report synthesis and structures of two dioxomolybdenum(VI) complexes with the general formula [MoO2L(CH3OH)], where L = L1 = (4-nitro-phenoxy)acetic acid [1-(3-ethoxy-2-hydroxyphe-nyl)methylidene]hydrazide (H2L1) and L = L2 = (4-nitrophenoxy)acetic acid [1-(5-bromo-2-hydroxy-phenyl)methylidene]hydrazide (H2L2).
N' OH
OEt
H ,N.
O
no2
Br
O
(H2L1)
N' OH
H -N.
O
O
(H2L2)
no2
EXPERIMENTAL
Materials and measurements. Commercially available 3-ethoxysalicylaldehyde, 5-bromosalicylaldehyde, and (4-nitrophenoxy)acetic acid hydrazide were purchased from Aldrich and used without further purification. Other solvents and reagents were made in China and used as received. C, H, and N elemental anal-
yses were performed with a PerkinElmer elemental analyser. The infrared spectra were recorded on a Nicolet AVATAR 360 spectrometer as KBr pellets in the 4000-400 cm-1 region.
Synthesis of H2L1. 3-Ethoxysalicylaldehyde (1.0 mmol, 0.166 g) and (4-nitrophenoxy)acetic acid hydrazide (1.0 mmol, 0.211 g) were dissolved in meth-
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QIAN et al.
anol (30 mL) with stirring. The mixture was stirred for about 30 min at room temperature to give a yellow solution. The solvent was evaporated to give yellow crystalline product of H2L1. The yield was 91%.
For C17H17N3O6 anal. calcd., %: Found, %:
C, 56.82; C, 56.65;
H, 4.77; H, 4.68;
N, 11.69. N, 11.57.
Synthesis of H2L2. 5-Bromosalicylaldehyde (1.0mmol, 0.201 g) and (4-nitrophenoxy)acetic acid hydrazide (1.0 mmol, 0.211 g) were dissolved in methanol (30 mL) with stirring. The mixture was stirred for about 30 min at room temperature to give a yellow solution. The solvent was evaporated to give yellow crystalline product of H2L2. The yield was 94%.
For C15H12N3O5Br
anal. calcd., %: C, 45.71; H, 3.07; N, 10.66. Found, %: C, 45.59; H, 3.16; N, 10.53.
Synthesis of [MoO2(L1)(CH3OH)] (I). A methan-olic solution (10 mL) of [MoO2(Acac)2] (0.1 mmol, 32.6 mg) was added to a methanolic solution (10 mL) of H2L1 (0.1 mmol, 35.9 mg) with stirring. The mixture was stirred for 20 min to give an orange solution. The resulting solution was allowed to stand in air for a few days. Orange block-shaped crystals suitable for X-ray single crystal analysis were formed at the bottom of the vessel. The isolated product was washed three times with cold methanol and dried in a vacuum over anhydrous CaCl2. The yield was 62%.
For C18H19N3O9Mo
anal. calcd., %: C, 41.79; H, 3.70; N, 8.12. Found, %: C, 41.95; H, 3.77; N, 8.20.
Synthesis of [MoO2(L2)(CH3OH)] (II). A methan-olic solution (10 mL) of [MoO2(Acac)2] (0.1 mmol, 32.6 mg) was added to a methanolic solution (10 mL) of H2L2 (0.1 mmol, 39.4 mg) with stirring. The mixture was stirred for 20 min to give an orange solution. The resulting solution was allowed to stand in air for a few days. Orange block-shaped crystals suitable for X-ray single crystal analysis were formed at the bottom of the vessel. The isolated product was washed three times with cold methanol and dried in a vacuum over anhydrous CaCl2. The yield was 73%.
For C16H14N3O8BrMo
anal. calcd., %: C, 34.80; H, 2.56; N, 7.61. Found, %: C, 34.67; H, 2.50; N, 7.73.
X-ray structure determination. Diffraction intensities for the complexes were collected at 298(2) K using a Bruker D8 VENTURE PHOTON diffractometer with MoZ« radiation (X = 0.71073 A). The collected data were reduced using the SAINT program [11], and multi-scan absorption corrections were performed using the SADABS program [12]. The structures were solved by direct methods and refined against F2 by full-matrix least-squares methods using the SHELXTL [13]. All non-hydrogen atoms were refined anisotropically. The methanol H atoms in the complexes were located in difference Fourier maps and refined isotropically with O—H distances restrained to 0.85(1) A. All other H atoms were placed in idealized positions and constrained to ride on their parent atoms. The crystallographic data for the complexes are summarized in Table 1. Selected bond lengths and angles are given in Table 2.
Supplementary material for structures I and II has deposited with the Cambridge Crystallographic Data Centre (nos. 897243 (I), 897244 (II); deposit@ccdc. cam.ac.uk or http://www.ccdc.cam.ac.uk).
RESULTS AND DISCUSSION
Replacement of two acetylacetonate ligands in [MoO2(Acac)2] by hydrazone ligands resulted in the formation of mononuclear molybdenum(VI) oxo-complexes. In both complexes, the dinegative ligands are coordinated to the cis-MoO2 cores via the pheno-late-oxygen, imino-nitrogen, and enolate-oxygen atoms. The sixth coordination site is occupied by the oxygen atom from the methanol solvent. The complexes are soluble in methanol, ethanol, and acetonitrile. The molar conductance of the complexes I and II at the concentrations of 10-4 mol/L are 8 and 11 fi-1 cm2 mol-1, respectively, indicating they are non-electrolytes.
The molecular structures and the atom numbering schemes of the complexes I and II are shown in Fig. 1. The coordination geometry around each Mo atom is highly distorted octahedral. In each complex, the hydrazone ligand behaves in a tridentate manner in which the phenolate O, imino N, and enolate O atoms occupy a meridonial plane. The coordination geometry around molybdenum can be described as distorted octahedral in the complexes. The dianionic hydrazone ligands act in planar tridentate manner, forming one five- and one six-membered chelate rings involving the MoO2 core. The hydrazone ligand in each of the complexes is bonded to the MoO2 core in a planar fashion, coordinating through the phenolate O, imino N, and enolate O atoms and an oxogroup lying trans to the nitrogen donor. In each of the complexes, a methanol molecule completes the distorted octahe-
KOOP,3HHAUHOHHAH XHMH3 tom 40 № 2 2014
TWO MONONUCLEAR MOLYBDENUM(VI) OXO COMPLEXES
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Table 1. Crystallographic data and refinement parameters for complexes I and II
Parameter Value
I II
M 517.3 552.2
Crystal color, habit Orange, block Orange, block
Crystal size, mm 0.17 x 0.15 x 0.15 0.32 x 0.30 x 0.27
Crystal system Triclinic Triclinic
Space group P1 P1
Unit cell parameters:
a, A 7.4919(17) 7.5508(12)
b, A 8.423(2) 8.458(2)
c, A 18.343(2) 16.349(3)
a, deg 80.482(2) 91.254(2)
P, deg 81.975(3) 90.887(2)
Y, deg 72.458(2) 107.660(2)
V, A3 1083.5(4) 994.5(3)
Z 2 2
Pcalcd g cm-3 1.586 1.844
p., mm-1 0.659 2.717
/(000) 524 544
Number of unique data 4576 4232
Number of observed data (I > 2ct(T)) 3856 2676
Number of parameters 285 266
R1, wR2 (I > 2ct(T)) 0.0504, 0.1274 0.0568, 0.0860
R1, wR2 (all data) 0.0615, 0.1348 0.1058, 0.0982
Goodness of fit on F 2 1.029 0.988
^max^mim « A~3 1.069/-1.206 0.554/-0.612
Table 2. Selected bond distances (A) and angles (deg) for complexes I and II
Bond d, A Bond d, A
Mo(1)-O(1) Mo(1)-O(7) Mo(1)-N(1) 1.908(3) 1.695(3) 2.242(3) I Mo(1)-O(6) Mo(1)-O(8) Mo(1)-O(9) II Mo(1)-O(2) Mo(1)-O(7) Mo(1)-O(8) 2.026(3) 1.697(3) 2.337(3)
Mo(1)-O(1) Mo(1)-O(6) Mo(1)-N(1) 1.902(4) 1.676(4) 2.235(4) 2.021(3) 2.335(4) 1.699(3)
Angle ro, deg Angle ro, deg
O(7)Mo(1)O(8) O(8)Mo(1)O(1) O(8)Mo(1)O(6) O(7)Mo(1)N(1) O(1)Mo(1)N(1) O(7)Mo(1)O(9) O(1)Mo(1)O(9) N(1)Mo(1)O(9) 105.33(16) 104.60(14) 95.71(13) 96.65(14) 81.56(12) 170.85(13) 82.53(14) 74.98(12) I O(7)Mo(1)O(1) O(7)Mo(1)O(6) O(1)Mo(1)O(6) O(8)Mo(1)N(1) O(6)Mo(1)N(1) O(8)Mo(1)O(9) O(6)Mo(1)O(9) 100.12(16) 94.51(15) 150.67(13) 155.51(14) 71.54(12) 82.26(13) 79.46(13)
II
O(6)Mo(1)O(8) 104.90(17) O(6)Mo(1)O(1) 100.10(17)
O(8)Mo(1)O(1) 105.10(15) O(6)Mo(1)O(2) 94.32(16)
O(8)Mo(1)O(2) 95.15(15) O(1)Mo(1)O(2) 151.02(14)
O(6)Mo(1)N(1) 97.08(16) O(8)Mo(1)N(1) 155.31(16)
O(1)Mo(1)N(1) 81.51(15) O(2)Mo(1)N(1) 71.80(14)
O(6)Mo(1)O(7) 171.27(15) O(8)Mo(1)O(7) 82.22(15)
O(1)Mo(1)O(7) 82.56(15) O(2)Mo(1)O(7) 79.84(14)
N(1)Mo(1)O(7) 75.00(13)
KOOP^HH^HOHHAtf XHMHfl TOM 40 № 2 2014
(b)
O(5)
C(16)
Fig. 1. ORTEP p
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