Study on synthesis and crystal structure of an unexpected dialkoxo-bridged dinuclear Cu(II) complex

Article abstract of DOI:10.1080/15533174.2011.613889

An unprecedented dinuclear copper(II) complex, [Cu₂(L ²)₂] (H₂L² = 3- Methoxysalicylaldehyde O-(2-hydroxyethyl)oxime), has been synthesized via the complexation of copper(II) acetate monohydrate with unsymmetrical Salen-type ligand H₂L¹ (H₂L¹ = 3-Methoxy-2,2'-[ethylenedioxybis(nitrilomethylidyne)]diphenol). The crystal structure of the copper(II) complex has been determined by single-crystal X-ray diffraction method. The catalysis of copper(II) ions results in the unexpected cleavage of one of the NO bonds in the ligand H₂L¹, giving a novel dialkoxo-bridged dinuclear copper(II) complex possessing a CuOCuO four-membered ring core instead of the usually desired Salen-type bisoxime Cu-N₂O₂ mononuclear complex. Copyright Taylor & Francis Group, LLC.

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Synthesis and Reactivity in Inorganic, Metal-Organic,
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Study on Synthesis and Crystal Structure of an
Unexpected Dialkoxo-Bridged Dinuclear Cu(II) Complex
Wen-Kui Dong a , Shou-Ting Zhang a , Yin-Xia Sun a , Yuan Wang a & Li Wang a
a School of Chemical and Biological Engineering, Lanzhou Jiaotong University , Lanzhou ,
Gansu , P. R. China
Accepted author version posted online: 14 Mar 2012.Published online: 01 May 2012.
To cite this article: Wen-Kui Dong , Shou-Ting Zhang , Yin-Xia Sun , Yuan Wang & Li Wang (2012) Study on Synthesis and
Crystal Structure of an Unexpected Dialkoxo-Bridged Dinuclear Cu(II) Complex, Synthesis and Reactivity in Inorganic, Metal-
Organic, and Nano-Metal Chemistry, 42:4, 583-589, DOI: 10.1080/15533174.2011.613889
To link to this article: http://dx.doi.org/10.1080/15533174.2011.613889
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 42:583–589, 2012
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.613889
Study on Synthesis and Crystal Structure of an Unexpected
Dialkoxo-Bridged Dinuclear Cu(II) Complex
Wen-Kui Dong, Shou-Ting Zhang, Yin-Xia Sun, Yuan Wang, and Li Wang
School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu,
P. R. China
[ CH N (CH2)n N CH ] group, the large electroneg-
An unprecedented dinuclear copper(II) complex, [Cu2(L2)2]
(H2L2 = 3-Methoxysalicylaldehyde O-(2-hydroxyethyl)oxime),
has been synthesized via the complexation of copper(II) acetate
monohydrate with unsymmetrical Salen-type ligand H2L1 (H2L1 =
3-Methoxy-2,2ꢀ-[ethylenedioxybis(nitrilomethylidyne)]diphenol).
The crystal structure of the copper(II) complex has been deter-
mined by single-crystal X-ray diffraction method. The catalysis
of copper(II) ions results in the unexpected cleavage of one of the
ativity of oxygen atoms is expected to affect strongly the
electronic properties of the N2O2 coordination sphere, which
can lead to different and novel properties and structures of the
resulting complexes.[7–10] The reported copper(II) complexes
with symmetrical Salen-type bisoxime ligands show structures
of 1:1,[11–13] 2:2,[14] 3:2,[12,15] and 4:2(Cu:L).[16] Although the
studies of Salen-type bisoxime complexes have made great
progress,[17–19] it has not been found the cleavage of N O
bonds of unsymmetrical Salen-type bisoxime ligands when
the ligands are allowed to react with metal salt, consequently,
gained a unexpected complex with the new ligands.
N
O bonds in the ligand H2L1, giving a novel dialkoxo-bridged
dinuclear copper(II) complex possessing a Cu Cu O four-
O
membered ring core instead of the usually desired Salen-type
bisoxime Cu N2O2 mononuclear complex.
In this article, we report the synthesis and structural
characterization of a copper(II) complex with new ligand, H2L2
(H2L2 = 3-methoxysalicylaldehyde O-(2-hydroxyethyl)oxime),
which is formed in course of the complexation of an unsym-
metrical Salen-type bisoxime ligand, H2L1 {3-Methoxy-
Keywords complexation behavior, copper(II) complex, crystal struc-
ture, synthesis, unsymmetrical Salen-type ligand
INTRODUCTION
2,2ꢁ-[ethylenedioxybis(nitrilomethylidyne)]diphenol},
and
Salen-type compounds and their metallosalen complexes
have been of considerable present interest due to their ubiq-
uitous use in a variety of catalytic chemical transformations.
Examples where Salen complexes offer both high reactivity
and selectivity include epoxidation of olefins, asymmetric ring
opening of epoxides, olefin aziridination, olefin cyclopropana-
tion, and formation of cyclic and linear polycarbonates.[1] And
can be used to obtain non-linear optical materials,[2] biologi-
cal systems,[3] interesting magnetic properties,[4] and building
blocks for cyclic supramolecular structures.[5] Thus, new mate-
rials can be produced by using these compounds, which seem
to be suitable candidates for further chemical modifications.[6]
Recently, a preferable class of Salen-type bisoxime
ligands was reported, using an O-alkyloxime unit
copper(II) acetate monohydrate. The obtained results show
cleavage of one of the N O bonds in H2L1 in the com-
plexation of unsymmetrical Salen-type ligand H2L1 with
copper(II) acetate monohydrate, and giving an unexpected
dialkoxo-bridged dinuclear copper(II) complex possessing a
Cu O Cu O four-membered ring core instead of the usually
desired Salen-type bisoxime Cu N2O2 complex.
EXPERIMENTAL
Materials and Instruments
All chemicals were of analytical reagent grade and were
used without further purification. C, H, and N analyses were ob-
tained using a GmbH VarioEL V3.00 automatic elemental anal-
ysis instrument. Elemental analysis for Cu was detected by an
IRIS ER/S·WP–1 ICP atomic emission spectrometer. IR spectra
were recorded on a Bruker VERTEX70 FT-IR spectrophotome-
[ CH N O (CH2)n O N CH ]
instead
of
the
Received 20 July 2011; accepted 9 August 2011.
This work was supported by the Foundation of the Education De- ter, with samples prepared as KBr (500–4000 cm−1) and CsI
(100–500 cm−1) pellets. Electrolytic conductance measurement
partment of Gansu Province and the ‘Jing Lan’ Talent Engineering
Funds of Lanzhou Jiaotong University, which are gratefully acknowl-
was made with a DDS–11D type conductivity bridge using a 1.0
edged.
× 10−3 mol·L−1 solution in DMF at room temperature. 1H NMR
Address correspondence to Wen-Kui Dong, School of Chemical
spectra were determined by German Bruker AVANCE DRX-
400 spectroscopy (Madison, WI, USA). X-ray single-crystal
and Biological Engineering, Lanzhou Jiaotong University, Lanzhou,
730070, P. R. China. E-mail: dongwk@126.com
583

584
W.-K. DONG ET AL.
SCH. 1. Synthetic route of 3-Methoxy-2,2ꢁ-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H2L1).
structure determination was carried out on a Bruker Smart Apex The mixture solution was heated at 55–60◦C for 5 h, and the
CCD diffractometer. Melting points were obtained by use of a solution was concentrated in vacuo, yielding 99.1 mg white
microscopic melting point apparatus made in Beijing Taike In- needle-like crystals after recrystallization (chloroform/hexane).
strument Limited Company (P. R. China) and were uncorrected.
Yield 60%. m.p. 80.5∼81.5◦C. Anal. Calcd. for C17H18N2O5
(%): C, 61.81; H, 5.49; N, 8.48;. Found: C, 61.65; H, 5.40; N,
8.63. 1H NMR (400 MHz, CDCl3) δ 3.90 (s, 3H), 4.50 (s, 4H),
6.81 (dd, J = 7.6, 1.8 Hz, 1H), 6.87 (t, J = 7.6 Hz, 1H), 6.91
(t, J = 7.9 Hz, 1H), 6.93 (dd, J = 7.6, 1.6 Hz, 1H), 6.99 (d, J
= 7.8 Hz, 1H), 7.17 (dd, J = 7.8, 1.6 Hz, 1H), 7.29 (t, J = 7.8
Hz, 1H), 8.24 (s, 1H), 8.26 (s, 1H), 9.76 (s, 1H), 9.78 (s, 1H).
13C NMR (100 MHz, CDCl3) δ 56.4 (CH3), 72.7 (CH2), 73.0
(CH2), 113.4 (CH), 116.2 (C), 116.5 (C), 116.8 (CH), 119.5
(CH), 119.7 (CH), 122.5 (CH), 130.9 (CH), 131.2 (CH), 147.1
(C), 148.0 (C), 151.9 (CH N), 152.5 (CH N), 157.7 (C).
Syntheses of H2L1
The major reaction steps involved in the synthesis of the
unsymmetrical Salen-type chelate ligand H2L1 {3-Methoxy-
2,2ꢁ-[ethylenedioxybis(nitrilomethylidyne)]diphenol} are given
in Scheme 1.
1,2-Bis(phthalimidoxy)ethane was prepared according to the
literature.[8,9] Yield 95.6%. m.p. 250◦C.
1,2-Bis(aminooxy)ethane was synthesized according to an
analogous method reported previously.[10,12] 1H NMR (400
MHz, CDCl3, d, ppm): 3.79 (s, 4H), 5.52 (s, 4H).
Synthesis of [Cu2(L2)2]
Monooxime compound was synthesized according to an
analogous method reported previously in the literature.[18–20]
To an ethanol solution (4 mL) of 1,2-bis(aminooxy)ethane (97.7
mg, 1.06 mmol) was added dropwise the ethanol solution (6 mL)
of 2-hydroxy-3-methoxybenzaldehyde (80.7 mg, 0.53 mmol).
The mixture solution was heated at 50–55◦C for 2 h, and the
solution was concentrated in vacuo and yielding 94.2 mg white
needle-like crystals after recrystallization (chloroform/hexane).
Yield 78.6%. m.p. 96–97◦C, Anal. Calcd. for C10H14N2O4: C,
53.09; H, 6.24; N, 12.38; Found: C, 52.90; H, 6.26; N, 12.27.
1H NMR (400 MHz, CDCl3) δ 3.91 (s, 3H), 3.97 (t, J = 4.4 Hz,
2H), 4.37 (t, J = 4.4 Hz, 2H), 5.52 (brs, 2H), 6.81 (dd, J = 7.7,
1.6 Hz, 1H), 6.86 (t, J = 7.7 Hz, 1H), 6.91 (dd, J = 7.7, 1.6
Hz, 1H), 8.23 (s, 1H), 9.87 (s, 1H); 13C NMR (75 MHz, CDCl3)
δ 56.0 (CH3), 72.5 (CH2), 73.6 (CH2), 113.2 (CH), 116.4 (C),
A solution of copper(II) acetate monohydrate (3.49 mg, 0.018
mmol) in ethanol (3 mL) was added dropwise to a solution
of H2L1 (4.01 mg, 0.012 mmol) in hot ethanol (3 mL). The
color of the mixing solution turned to brown immediately, and
then stirring was continued for 2 h at room temperature. The
mixture was filtered and the filtrate was allowed to stand at room
temperature for about three weeks, the solvent was partially
evaporated and obtained pale-brown block-like single crystals
suitable for X-ray crystallographic analysis. Anal. Calcd. for
C20H22Cu2N2O8 [Cu2(L2)2] (%): C, 44.04; H, 4.07; N, 5.14;
Cu, 23.30. Found: C, 44.01; H, 4.09; N, 5.24; Cu, 23.28.
Data Collection, Structure Determination, and
Refinement
X-ray diffraction data were collected on a Bruker Smart Apex
119.3 (CH), 122.1 (CH), 146.9 (C), 148.0 (C), 151.3 (CH N). CCD diffractometer at (294 2) K using graphite monochro-
For 3-Methoxy-2,2ꢁ-[ethylenedioxybis(nitrilomethylidyne)] matized Cu Kα radiation (λ = 1.54187 Å). Unit cell parame-
diphenol (H2L1), to an ethanol solution (10 mL) of monooxime ters were determined by least-squares analysis. The LP factor
compound (113.1 mg, 0.50 mmol), the ethanol solution (10 mL) and semiempirical absorption corrections were applied to the
of 2-hydroxybenzaldehyde (61.0 mg, 0.50 mmol) was added intensity data. The structure was solved by the direct method
dropwise, and the color of the mixture turned into pale yellow. (SHELXS-97) and subsequent difference-Fourier map revealed

AN UNEXPECTED DIALKOXO-BRIDGED CU(II) COMPLEX
585
TABLE 1
Crystal data and structure refinement for complex [Cu2(L2)2]
Empirical formula
C20H22Cu2N2O8
Absorption correction
F (000)
Crystal size / mm
θ Range for data collection /(◦)
Index ranges
Semiempirical from equivalents
Formula weight
T / K
Wavelength / Å
Crystal system
545.48
294(2)
278
0.20 × 0.16 × 0.04
1.54187
Tricl−inic
2.125 to 35.995
-5 ≤ h ≤ 4, -11 ≤ k ≤ 11, -13 ≤ l ≤ 13
96.4
Space group
a / (Å)
b / (Å)
c / (Å)
α / (◦)
β / (◦)
γ / (◦)
V / Å3
Z
P
Completeness to θ = 33.875 (%)
Reflections collected
Independent reflections
Refinement method
1
5.0370(7)
9.759(1)
10.973(1)
106.222(9)
98.070(9)
92.150(8)
511.1(1)
1
7798
1897 [R(int) = 0.0429]
Full-matrix least-squares on F2
1897/0/146
Data / restraints /parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
R indices (all data)
1.158
R1 = 0.0525, wR2 = 0.1509
R1 = 0.0529, wR2 = 0.1511
0.456
−0.437
(ꢀρ)max/(e·Å− 3
)
)
Dc / (Mg · m−3
)
1.772
(ꢀρ)min/(e·Å− 3
the positions of the remaining atoms, and all hydrogen atoms is soluble in aforementioned solvents. Molar conductance values
were added theoretically. All non-hydrogen atoms were refined of complex [Cu2(L2)2] at 18◦C of 1.0 × 10−3 mol·L−1 DMF
anisotropically using a full-matrix least-squares procedure on solutions are 3.8 S·cm2·mol−1, indicating the complex is non-
F2 with SHELXL-97. Anisotropic thermal parameters were as- electrolyte. This implies that the two Cu(II) ions in complex
signed to all non-hydrogen atoms. The hydrogen atoms were [Cu2(L2)2] are firmly held in the coordination sphere in solution.
generated geometrically. The crystallographic data and struc-
tural refinements for the complex are listed in Table 1.
IR Spectra Analyses
The FT-IR spectra of H2L1 and complex [Cu2(L2)2] exhibit
various bands in the 500–4000 cm−1 region. Some important IR
RESULTS AND DISCUSSION
absorption bands are listed in Table 2. The O H stretching fre-
quency of the Salen-type ligands is expected in the 3300–3800
cm−1 region, however, this frequency is generally displaced to
ca. 3431 cm−1 due to the internal hydrogen bond OH N C.[21]
Thus, each unit of the polymeric ligands behaves as a diba-
sic tetradentate ONNO donor. As the hydrogen bond becomes
stronger, the bandwidth increases, and this band sometimes is
not detected. Electron-donating groups on the phenolic ring in-
crease the electron density on the hydroxyl oxygen making the
H O bond stronger, the absorption usually appears as a broad
band in the FT-IR spectrum. For the Cu(II) complex, the dis-
By the condensation of the monooxime compound with 2-
hydroxybenzaldehyde, it can give rise to a unsymmetrical Salen-
type ligand, which was easily identified by its IR spectrum,
where replacement of the carbonyl by the imine group results in
lowering of the energy of the ν(C O) stretch. The unsymmetrical
Salen-type ligand prepared in this way is formed in nearly quan-
titative yield and is of high purity. The results of the elemental
analyses are in accord with the composition suggested for the
unsymmetrical Salen-type ligand and the Cu(II) complex.
Molar Conductances
Complex [Cu2(L2)2] is soluble in DMF and DMSO, slightly appearance of this band is expected due to the substitution of
soluble in CHCl3, but not soluble in EtOH, MeOH, MeCN, hydrogen for the Cu(II) ion when the complex formed.[22]
THF, acetone, and ethyl acetate. The complex displays good
The free ligand H2L1 exhibits characteristic C N stretching
stability in air at room temperature. Meanwhile, the ligand H2L1 band at 1619 cm−1, while the C N of the Cu(II) complex is
TABLE 2
The most important FT-IR bands for the ligands and complex [Cu2(L2)2] (cm−1
)
Compound
ν(O
ν(C
ν(Ar
ν(Cu
ν(Cu
O)
ν(C C) benzene ring skeleton
H)
N)
O)
N)
H2L1
3477
-
1619
1608
1235
1248
-
-
1537, 1472, 1406
1575, 1504, 1408
[Cu2(L2)2]
475
433

586
W.-K. DONG ET AL.
observed in the 1608 cm−1. The C N stretching frequency is
shifted to lower frequency by ca. 11 cm−1 upon complexation,
indicating a decrease in the C N bond order due to the coor-
dination bonds of the Cu(II) ion with the oxime nitrogen lone
pair.[23] In the 1403–1608 cm−1 region, the observed bands are
attributed to aromatic C C vibrations. Upon coordination these
bands shift to lower frequencies for the Cu(II) complexes.[24]
The Ar O stretching frequency appears as a strong band
within the 1263–1213 cm−1 as reported for similar ligands.[22]
This band occurs at 1235 cm−1 for the ligand H2L1, and at 1248
cm−1 for the Cu(II) complex. The Ar O stretching frequency
is shifted to a higher frequency, indicating that the Cu O bond
is formed between the Cu(II) ion and oxygen atoms of phenolic
group.[23,24]
Thornton,[25] the metal–oxygen and metal–nitrogen frequency
assignments are at times very difficult.
Description of Crystal Structure
The synthesis of copper(II) complex was used the same syn-
thetic route for the mononuclear complex according to our previ-
ous work.[12,13] However, it is remarkable that it did not form the
desired unsymmetrical Salen-type bisoxime complex [Cu(L1)],
but obtained a unexpected copper(II) complex [Cu2(L2)2], which
was formed in the course of the complexation of H2L1 and cop-
per(II) acetate monohydrate. The results indicate the complex-
ation of the ligand H2L1 with copper(II) acetate monohydrate
resulted in cleavage of one of the N O bonds in H2L1,[26,27] giv-
ing a new O N O tridentate ligand H2L2, which coordinates to
Cu(II) ions forming an dialkoxo-bridged dinuclear Cu(II) com-
plex with a Cu O Cu O four-membered ring core instead
of the usually desired Salen-type bisoxime Cu N2O2 complex
(Figure 1).[11–14]
The far-infrared spectrum of complex [Cu2(L2)2] is also ob-
tained in the region of 500–100 cm−1 in order to identify fre-
quencies due to the Cu O and Cu N bonds. The band at 433
cm−1 in Cu(II) complex is assigned to ν(Cu O), while band at
475 cm−1 is assigned to ν(Cu N). These bands are observed
as new peaks for complex [Cu2(L2)2] and are not present in the
spectrum of the free ligand H2L1. As pointed out by Percy and
The crystal structure and atom numbering of complex
[Cu2(L2)2] are shown in Figure 2. Selected bond lengths and
bond angles are listed in Table 3.
FIG. 1. Complexation of the ligand H2L1 with copper(II) acetate and chemical structure of H2L2.

AN UNEXPECTED DIALKOXO-BRIDGED CU(II) COMPLEX
587
FIG. 2. Molecular structure and atom numbering of complex [Cu2(L2)2].
Single-crystal X-ray structure reveals the complex is a cen- bridges, each of which comes from the individual new ligand
trosymmetric neutral homobinuclear entity. Because of the H2L2. The whole complex sits on a crystallographically inverse
catalysis of copper(II) ions,[27] the complexation of the ligand center forming the µ-dialkoxo-bridged binuclear structure with
H2L1 with copper(II) acetate monohydrate resulted in the unex- both tetra-coordinated Cu(II) centers. The local coordination
pected cleavage of one of the N O bonds in the ligand H2L1, environment is exactly identical for both centers, which can be
giving a novel dialkoxo-bridged dinuclear copper(II) complex best described as a slightly distorted square plane with CuN1O3
possessing a Cu O Cu O four-membered ring core instead (one oxime nitrogen atom N1, one phenoxo oxygen atom O2,
of the usually desired Salen-type bisoxime Cu N2O2 complex. and two bridging alkoxo oxygen atoms O3 and O3−1), as ev-
ORTEP illustration of the complex shows that two [Cu(L2)] idenced from Figure 2. Thus, a planar Cu2O2 core is formed
moieties in a same molecule are bridged together via two alkoxo by two divalent copper(II) ions and their bridging two alkoxo
FIG. 3. Crystal structure of complex [Cu2(L2)2] showing the polymeric array. (Color figure available online).

588
W.-K. DONG ET AL.
TABLE 3
Selected bond distances (Å) and bond angles (◦) for complex [Cu2(L2)2]
Bond
Dist.
Bond
Dist.
Cu(1)-O(1)
Cu(1)-O(3)#1
Cu(1)-Cu(1)#1
O(2)-N(1)
O(3)-C(9)
O(4)-C(6)
N(1)-C(7)
C(1)-C(6)
C(2)-C(7)
C(4)-C(5)
C(8)-C(9)
1.875(3)
1.922(3)
2.9995(1)
1.412(4)
1.405(5)
1.338(6)
1.290(6)
1.424(6)
1.425(6)
1.383(8)
1.502(6)
Cu(1)-O(3)
Cu(1)-N(1)
O(1)-C(1)
O(2)-C(8)
O(3)-Cu(1)#1
O(4)-C(10)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(5)-C(6)
1.906(3)
1.939(3)
1.320(5)
1.443(5)
1.922(3)
1.422(7)
1.404(6)
1.423(6)
1.347(8)
1.386(7)
Bond
Angle
Bond
Angle
O(1)-Cu(1)-O(3)
O(3)-Cu(1)-O(3)#1
O(3)-Cu(1)-N(1)
O(1)-Cu(1)-Cu(1)#1
O(3)#1-Cu(1)-Cu(1)#1
C(1)-O(1)-Cu(1)
C(9)-O(3)-Cu(1)
Cu(1)-O(3)-Cu(1)#1
C(7)-N(1)-O(2)
O(2)-N(1)-Cu(1)
O(1)-C(1)-C(6)
C(1)-C(2)-C(3)
C(3)-C(2)-C(7)
C(3)-C(4)-C(5)
C(4)-C(6)-C(5)
C(5)-C(6)-C(1)
O(2)-C(8)-C(9)
170.9(1)
76.7(1)
93.8(1)
O(1)-Cu(1)-O(3)#1
O(1)-Cu(1)-N(1)
O(3)#1-Cu(1)-N(1)
O(3)-Cu(1)-Cu(1)#1
N(1)-Cu(1)-Cu(1)#1
N(1)-O(2)-C(8)
C(9)-O(3)-Cu(1)#1
C(6)-O(4)-C(10)
C(7)-N(1)-Cu(1)
O(1)-C(1)-C(2)
C(2)-C(1)-C(6)
C(1)-C(2)-C(7)
C(4)-C(3)-C(2)
C(4)-C(5)-C(6)
O(4)-C(6)-C(1)
N(1)-C(7)-C(2)
O(3)-C(9)-C(8)
94.3(1)
93.8(1)
171.7(1)
38.59(8)
133.7(1)
110.3(3)
129.9(3)
117.4(5)
125.5(3)
124.9(4)
117.1(4)
122.8(4)
120.9(5)
120.7(5)
114.9(4)
125.6(4)
111.4(3)
132.46(9)
38.22(8)
127.1(3)
125.9(2)
103.2(1)
111.9(3)
122.3(2)
118.0(4)
120.2(4)
117.0(4)
120.2(5)
124.2(4)
120.8(4)
112.1(4)
Symmetry transformations used to generate equivalent atoms: #1, −x + 1, −y, −z + 1.
The complex is stabilized by two pairs of C8 H8A···O1 and
C8 H8A···O4 hydrogen bonds linking both molecules into a
1D infinite chain parallel to the a axis. The C8H8A groups
are hydrogen-bonded to the phenoxo oxygen (O1) atom and
the oxygen (O4) atom of the methoxy group of the (L2)2− unit,
respectively (Table 4).
oxygen atoms with a Cu Cu separation of 2.9995 Å. The dis-
tance of Cu1–Cu1#1 is relatively too long to be considered as
intramolecular Cu Cu bonding.
The bridging Cu O bonds are slightly asymmetric with one
being short, Cu1 O3 = 1.906 Å and one long Cu1 O3#1
=
1.922 Å. The bond distance of Cu1 O1 and Cu1 N1 are 1.875
Å and 1.939 Å, respectively. The two planes O3 Cu1 O3#1
and O3 Cu1#1 O3#1 are parallel to each other, indicating
Cu1, Cu1#1, O2, and O2#1 are coplanar exactly. The angles
of Cu1 O3 Cu1#1 and O3 Cu1 O3#1 are 103.3◦ and 76.7◦,
respectively. The dihedral angle of two planes O3 Cu1 O3#1
and O1 Cu1 N1 is 2.86◦, and the Cu1 atom deviates by 0.004
Å from the mean plane defined by the atoms O3, O3#1, O1, N1.
The polymeric array of complex [Cu2(L2)2] is given in Fig-
ure 3, which is formed by the packing of the complex molecules.
TABLE 4
Hydrogen-bonding (Å, ◦) of complex [Cu2(L2)2]
D H···A
d(D H)
d(H···A)
DHA
d(D···A)
C8 H8A···O1
0.970
0.970
2.576
2.617
156.45
156.30
3.486
3.200
C8 H8A···O4

AN UNEXPECTED DIALKOXO-BRIDGED CU(II) COMPLEX
589
CONCLUSION
10. Dong, W. K.; Shi, J. Y.; Zhong, J. K.; Tian,Y. Q.; Duan, J. G. Synthe-
sis, crystal structure and Infrared spectral analysis for a novel trinuclear
nickel(II) cluster. Chinese J. Inorg. Chem. 2008, 24, 10–14.
11. Akine, S.; Taniguchi, T.; Nabeshima, T. Synthesis and characterization of
novel ligands 1,2-bis(salicylideneaminooxy)ethanes. Chem. Lett. 2001, 30,
682–683.
12. Dong, W. K.; Sun, Y. X.; He, X. N.; Tong, J. F.; Wu, J. C. Trinu-
clear and mononuclear copper(II) complexes incorporating tetradentate
2,2ꢁ-[1,1ꢁ-(ethylenedioxydinitrilo)diethylidyne]diphenol ligand: Syntheses,
crystal structures, spectral and thermal behaviors, Spectrochim. Acta, Part
A 2010, 76, 476–483.
In a summary, an unprecedented dinuclear copper(II) com-
plex, [Cu2(L2)2], bearing a 2:2 ligand:metal stoichiometry,
have been synthesized from ligand H2L1 by the reaction with
Cu(OAc)2·H2O in moderate yields. It is interesting that each
copper(II) ion in the complex is tetra-coordinated by two
monooxime (L2)2− units. The catalysis of copper(II) ions results
in the unexpected cleavage of one of the N O bonds in the lig-
and H2L1, giving a novel dialkoxo-bridged dinuclear copper(II)
complex possessing a Cu O Cu O four-membered ring core
instead of the usually desired Salen-type bisoxime Cu N2O2
complex.
13. Dong, W. K.; Lv, Z. W.; Sun, Y. X.; Xu, L.; Wang, L.; Dong, X. Y. Synthesis,
crystal structural and thermal properties of copper(II) and cobalt(II) com-
plexes with a Salen-type bisoxime ligand. Chinese J. Inorg. Chem. 2009,
25, 1627–1634.
14. Dong, W. K.; Tong, J. F.; Sun, Y. X.; Wu, J. C.; Yao, J.; Gong, S. S.
Studies on mono- and dinuclear bisoxime copper complexes with different
coordination geometries. Transition Met. Chem. 2010, 35, 419–426.
15. Dong, W. K.; He, X. N.; Yan, H. B.; Lv, Z. W.; Chen, X.; Zhao, C. Y.; Tang,
X. L. Synthesis, structural characterization and solvent effect of copper(II)
complexes with a variational multidentate Salen-type ligand with bisoxime
groups. Polyhedron 2009, 28, 1419–1428.
16. Dong, W. K.; Feng, J. H.; Wang, L.; Xu, L.; Zhao, L.; Yang, X. Q. Synthesis
and structural characterization of a novel tetranuclear Cu(II)complex:
[Cu4L2(pic)4(H2O)2]·2H2O. Transition Met. Chem. 2007, 32,
1101–1105.
17. Akine, S.; Taniguchi, T.; Nabeshima, T. Novel synthetic approach to trinu-
clear 3d-4f complexes: Specific exchange of the central metal of a trinuclear
zinc(II) complex of a tetraoxime ligand with a lanthanide(III) ion. Angew.
Chem. Int. Ed. 2002, 41, 4670–4673.
18. Dong, W. K.; Sun, Y. X.; Zhang, Y. P.; Li L.; He, X. N.; Tang, X. L.
Synthesis, crystal structure, and properties of supramolecular CuII, ZnII,
and CdII complexes with Salen-type bisoxime ligands. Inorg. Chim. Acta
2009, 362, 117–124.
19. Dong, W. K.; Duan, J. G.; Guan, Y. H.; Shi, J. Y.; Zhao, C. Y. Synthesis,
crystal structure and spectroscopic behaviors of Co(II) and Cu(II) com-
plexes with Salen-type bisoxime ligands. Inorg. Chim. Acta 2009, 362,
1129–1134.
20. Akine, S.; Taniguchi, T.; Dong, W. K.; Nabeshima, T. Oxime-based Salen-
type tetradentate ligands with high stability against imine metathesis reac-
tion. J. Org. Chem. 2005, 70, 1704–1711.
21. Dong, W. K.; Chen, X.; Sun, Y. X.; He, X. N.; Lv, Z. W.; Yan, H. B.; Tang,
X. L.; Zhao, C. Y. Synthesis and complexation behavior of a novel dialkoxo-
bridged dinuclear copper(II) complex with schiff base ligand. Chinese J.
Inorg. Chem. 2008, 24, 1325–1330.
22. Ueno, K.; Martel, A. E. Infrared studies on synthetic oxygen carriers. J.
Phys. Chem. 1956, 60, 1270–1275.
SUPPLEMENTARY MATERIALS
Crystallographic data have been deposited with the Cam-
bridge Crystallographic Data Centre as supplementary pub-
lication, No. CCDC 832646 for the complex. Copies of
the data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB21EZ, UK (Tele-
phone: (44) 01223 762910; Fax: +44−1223-336033; E-mail:
deposit@ccdc.cam.ac.uk). These data can be also obtained free
of charge at www.ccdc.cam.ac.uk/conts/retrieving.htm
REFERENCES
1. Kim, J.; Chen, B.; Reineke, T. M.; Li, H.; Eddaoudi, M.; Moler, D. B.;
O’Keeffe, M; Yaghi, O. M. Assembly of metal-organic frameworks from
large organic and inorganic secondary building units: New examples and
simplifying principles for complex structures. J. Am. Chem. Soc. 2001, 123,
8239–8247.
2. Miyasaka, H.; Matsumoto, N.; Okawa, H.; Re, N.; Gallo, E.; Floriani, C.
Complexes derived from the reaction of manganese(III) Schiff base com-
plexes and hexacyanoferrate: Syntheses, multidimensional network struc-
tures and magnetic properties. J. Am. Chem. Soc. 1996, 118, 981–994.
3. Lacroix, P. G. Second-order optical nonlinearities in coordination chem-
istry: The case of bis(salicylaldiminato)metal Schiff base complexes. Eur.
J. Inorg. Chem. 2001, 339–348.
4. Ronson, T. K.; Adams, H.; Ward, M. D. Bis-bidentate bridging ligands
containing two N,O-chelating pyrazolyl-phenolate units; double helical
complexes with Co(II), Cu(II) and Zn(II). Inorg. Chim. Acta 2005, 358,
1943–1954.
5. Sharma, A. K.; Lloret, F.; Mukherjee, R. Phenolate- and acetate (Both
23. Kohawole, G. A.; Patel, K. S. The stereochemistry of oxovanadium(IV)
complexes derived from salicylaldehyde and polymethylenediamines. J.
Chem. Soc., Dalton Trans. 1981, 1241–1245.
24. Asadi, M.; Jamshid, K. A.; Kyanfar, A. H. Synthesis, characterization and
equilibrium study of the dinuclear adducts formation between nickel(II)
Salen-type complexes with diorganotin(IV) dichlorides in chloroform. In-
org. Chim. Acta 2007, 360, 1725–1730.
25. Percy, G. C.; Thornton, J. Infrared spectra of N-aryl salicylaldimine com-
plexes substituted in both aryl rings, J. Inorg. Nucl. Chem. 1973, 35,
2319–2327.
26. Bu, X. R.; You, X. Z.; Meng, Q. J. Studies on the mixed trimeric reaction
of Schiff bases and structures of related metal complexes. Comments Inorg.
Chem. 1990, 9, 221–244.
µ2-1,1 and µ2-1,3 mode)-bridged face-shared trioctahedral linear NiII
,
3
NiII2MII (M = Mn, Co) complexes: Ferro and anti ferromagnetic coupling.
Inorg. Chem. 2007, 46, 5128–5130.
6. Policar, C.; Lambert, F.; Cesario, M.; Morgenstern-badarau, I. An inorganic
helix [Mn(IPG)(MeOH)]n[PF6]n: structural and magnetic properties of a
syn-anti carboxylate-bridged manganese(II) chain involving a tetradentate
ligand. Eur. J. Inorg. Chem. 1999, 12, 2201–2207.
7. Akine, S.; Dong, W. K.; Nabeshima, T. Octanuclear zinc(II) and cobalt(II)
clusters produced by cooperative tetrameric assembling of oxime chelate
ligands. Inorg. Chem. 2006, 45, 4677–4684.
8. Dong, W. K.; Ding, Y. J. Growth and structural characterization of
[ZnL(DMSO)]. Cryst. Res. Technol. 2007, 43, 321–326.
9. Dong, W. K.; Shi, J. Y.; Zhong, J. K.; Sun, Y. X.; Duan, J. G. Synthesis and
structural characterization of a novel tricobalt cluster with 4,4ꢁ-dichloro-
2,2ꢁ-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol. Struct. Chem.
2008, 19, 95–99.
27. Dong, W. K.; Chen, X.; Sun, Y. X.; He, X. N.; Lv, Z. W.; Yan, H. B.; Tang,
X. L.; Zhao, C. Y. Synthesis and complexation behavior of a novel dialkoxo-
bridged dinuclear copper(II) complex with Schiff base ligand. Chinese J.
Inorg. Chem. 2008, 24, 1325–1330.