Zinc(II) and mercury(II) complexes [Zn((2,6-Cl-ba)2en)I 2] and [Hg((2,6-Cl-ba)2en)Br2] with the bidentate Schiff base ligand (2,6-Cl-ba)2en: Synthesis, characterization and crystal structures

Article abstract of DOI:10.1016/j.poly.2012.09.054

The zinc(II) and mercury(II) complexes [Zn((2,6-Cl-ba)₂en)I ₂] (1) and [Hg((2,6-Cl-ba)₂en)Br₂] (2) were prepared from the reaction of zinc(II) iodide and mercury(II) bromide with the bidentate Schiff base ligand (2,6-Cl-ba)₂en, having the systematic name [N,N′-bis(2,6-dichlorobenzylidene)ethane-1,2-diamine]. The two complexes were characterized by elemental analysis (CHN), FT-IR spectroscopy and X-ray single-crystal diffraction. The crystal structure analysis revealed that the coordination geometry around the metal ions in the two complexes is distorted tetrahedral. The Schiff base ligand (2,6-Cl-ba)₂en acts as a chelating ligand and coordinates via two nitrogen atoms to the metal centers.

Full text of DOI:10.1016/j.poly.2012.09.054

Polyhedron 49 (2013) 19–23
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Zinc(II) and mercury(II) complexes [Zn((2,6-Cl-ba)2en)I2] and
[Hg((2,6-Cl-ba)2en)Br2] with the bidentate Schiff base ligand (2,6-Cl-ba)2en:
Synthesis, characterization and crystal structures
b
b
c
Aliakbar Dehno Khalaji a, , Gholamhossein Grivani , Mohammad Seyyedi , Karla Fejfarova ,
⇑
Michal Dusek c
a Department of Chemistry, Faculty of Science, Golestan University, Gorgan, Iran
b School of Chemistry, Damghan University, Damghan, P.O. Box 36715-364, Iran
c Institute of Physics of the ASCR, v.v.i., Na Slovance 2, 182 21 Prague 8, Czech Republic
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 July 2012
Accepted 26 September 2012
Available online 8 October 2012
The zinc(II) and mercury(II) complexes [Zn((2,6-Cl-ba)2en)I2] (1) and [Hg((2,6-Cl-ba)2en)Br2] (2) were
prepared from the reaction of zinc(II) iodide and mercury(II) bromide with the bidentate Schiff base
ligand (2,6-Cl-ba)2en, having the systematic name [N,N0-bis(2,6-dichlorobenzylidene)ethane-1,2-dia-
mine]. The two complexes were characterized by elemental analysis (CHN), FT-IR spectroscopy and X-
ray single-crystal diffraction. The crystal structure analysis revealed that the coordination geometry
around the metal ions in the two complexes is distorted tetrahedral. The Schiff base ligand (2,6-Cl-ba)2en
acts as a chelating ligand and coordinates via two nitrogen atoms to the metal centers.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Zinc(II)
Mercury(II)
Schiff base
Single-crystal: tetrahedral
1. Introduction
purifications. Infrared spectra were recorded using KBr disks on a
FT-IR Perkin–Elmer spectrophotometer. Elemental analyses were
The coordination chemistry of zinc(II) and mercury(II) com-
plexes containing Schiff base ligands has been of interest in recent
years [1–9], because of its important role in the development of
coordination chemistry. These complexes have widely used photo-
luminescent properties [10] and they can also be utilized for the
construction of coordination polymers and networks [11–15].
Although the polymeric coordination chemistry of zinc(II) and
mercury(II) with Schiff base ligands has been extensively studied
[6,8,9,11–15], data on mononuclear zinc(II) and mercury(II) com-
plexes are relatively scarce [1–5,7,10].
In a continuation of our work on the preparation of zinc(II) and
mercury(II) complexes with symmetric bidentate Schiff base li-
gands [16–20], here we report the synthesis, spectroscopic studies
and crystal structures of zinc(II) and mercury(II) complexes with
the Schiff base ligand (2,6-Cl-ba)2en (Scheme 1).
carried out using a Heraeus CHN-O-Rapid analyzer. 1H NMR spec-
tra were measured on a BRUKER DRX-500 AVANCE spectrometer at
500 MHz. All chemical shifts are reported in d units downfield from
TMS.
2.2. Preparation of (2,6-Cl-ba)2en
(2,6-Cl-ba)2en was prepared by the condensation of 2,6-dichlo-
robenzaldehyde with ethane-1,2-diamine following method de-
scribed in [21]. Yield: 92%. Anal. Calc. for C16H12N2Cl4: C, 51.37;
H, 3.23; N, 7.49. Found: C, 51.40; H, 3.29; N, 7.55%. IR (KBr pellet,
cmꢀ1): 1641 (s, C@N).
2.3. Preparation of [Zn((2,6-Cl-ba)2en)I2] (1)
2. Experimental
To a stirring solution of the Schiff base ligand (2,6-Cl-ba)2en
(0.0374 g, 1 mmol) in 15 ml of chloroform was added ZnI2
(0.0319 g, 1 mmol) in 15 ml of hot methanol. The mixture was stir-
red for 0.5 h in air at 25 °C and then left at room temperature for
several days without disturbance, yielding micro crystals of 1.
Yield: 78%. Anal. Calc. for C16H12N2Cl4ZnI2: C, 27.72; H, 1.74; N,
4.04. Found: C, 27.80; H, 1.85; N, 4.11%. IR (KBr pellet, cmꢀ1):
1648 (s, C@N).
2.1. Materials and methods
All reagents and solvents for the syntheses and analyses were
commercially available and used as received without further
⇑
Corresponding author. Tel./fax: +98 171 4427050.
E-mail addresses: alidkhalaji@yahoo.com, ad.khalaji@gu.ac.ir (A.D. Khalaji).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.09.054

20
A.D. Khalaji et al. / Polyhedron 49 (2013) 19–23
Cl
Cl
N
N
Cl
Cl
Cl
Cl
N
N
Cl
Cl
N
N
HgBr2
ZnI2
Cl
Cl
Cl
Cl
Hg
Zn
Br
Br
I
I
Scheme 1. Chemical structures of Schiff base ligand (2,6-Cl-ba)2en and its zinc(II) and mercury(II) complexes.
2.4. Preparation of [Hg((2,6-Cl-ba)2en)Br2] (2)
harmonic functions successfully corrected for this effect. The
strongly absorbing compound 2 was measured with graphite-
To a stirring solution of the Schiff base ligand (2,6-Cl-ba)2en
(0.0374 g, 1 mmol) in 15 ml of chloroform was added HgBr2
(0.0361 g, 1 mmol) in 15 ml of hot methanol. The mixture was stir-
red for 0.5 h in air at 50 °C and then left at room temperature for
several days without disturbance, yielding micro crystals of 2.
Yield: 70%. Anal. Calc. for C16H12N2Cl4HgBr2: C, 26.16; H, 1.65; N,
3.81. Found: C, 26.22; H, 1.71; N, 3.89%. IR (KBr pellet, cmꢀ1):
1663 (s, C@N).
monochromated Mo Ka radiation (k = 0. 7107 Å). The crystal struc-
tures were solved by direct methods with the program SIR2002
[22] and refined with the JANA2006 program package [23] by the
full-matrix least-squares technique on F2. The molecular structure
plots were prepared by ORTEP III [24]. Hydrogen atoms were
mostly discernible in the difference Fourier maps and could be re-
fined to a reasonable geometry. According to common practice
they were nevertheless kept in ideal positions during the refine-
ment. The isotropic atomic displacement parameters of the hydro-
gen atoms were evaluated as 1.2–1.5 Ueq of the parent atom.
Crystallographic data and details of the data collection and struc-
ture solution and refinements are listed in Table 1.
2.5. Crystallography data collection and refinement
Suitable single crystals of 1 and 2 were chosen for an X-ray dif-
fraction study. Crystallographic measurements were done at 120 K
with a four circle CCD diffractometer, Gemini of Oxford Diffraction
3. Results and discussion
Ltd. For 1, mirror-collimated Cu K
a radiation (k = 1.5418 Å) was
used. The corresponding absorption coefficient was large (see
Table 1), but absorption corrections based on the crystal shape,
combined with absorption corrections based on the spherical
3.1. Synthesis and characterization
The reaction between (2,6-Cl-ba)2en and zinc(II) iodide or mer-
cury(II) bromide provided monomeric zinc(II) and mercury(II)
complexes, [Zn((2,6-Cl-ba)2en)I2] (1) and [Hg((2,6-Cl-ba)2en)Br2]
(2). The complexes are moderately soluble in common organic sol-
vents such as methanol, ethanol, chloroform, dichloromethane and
acetone, and are completely soluble in coordinating solvents such
as DMF and DMSO. In order to confirm the chemical composition
of both complexes, elemental analysis (CHN) was carried out on
the crystallized compounds.
The FT-IR spectra of the free ligand (2,6-Cl-ba)2en and the com-
plexes exhibit a characteristic band of the C@N group, which ap-
pears at 1641 cmꢀ1 for the ligand and is shifted in the complexes
to 1648 (1) and 1663 cmꢀ1 (2), due to the coordination of the azo-
methine group.
Table 1
Crystallographic data and structure refinement for 1 and 2.
1
2
Chemical formula
Formula weight
Crystal system
Space group
Z
C
16H12Cl4I2N2Zn
C16H12Br2Cl4HgN2
734.5
triclinic
693.3
monoclinic
P21/c
ꢀ
P1
4
4
T (K)
120
120
a (Å)
b (Å)
c (Å)
11.1234(6)
13.9349(6)
13.7380(6)
90
90.350(4)
90
8.2209(4)
14.8315(7)
18.4452(8)
72.086(4)
83.081(4)
78.056(4)
2089.73(18)
a
(°)
b (°)
c
(°)
V (Å3)
2129.40(17)
3.2. Crystal and molecular structure of 1
Wavelength
Tmin
Cu K
0.075
0.511
29.01
11059
3751
3170
0.030
1.72
0.031
0.076
226
0.91
a
Mo Ka
0.055
0.112
11.70
31.271
10230
7444
0.032
1.16
0.027
0.062
451
0.89
An ORTEP view of 1 with the atom-numbering scheme is
presented in Fig. 1. Selected bond distances and angles are given in
Table 2. As shown in Fig. 1, each zinc(II) ion is coordinated
with two iminic nitrogen atoms from the Schiff base ligand (2,6-
Cl-ba)2en and two iodine atoms in the formof strongly deformedtet-
rahedron. The organic Schiff base ligand acts as a chelating bidentate
ligand. The geometry around the zinc(II) center of this complex is
quite similar to the zinc(II) complexes [Zn((3,4-MeO-ba)2en)I2]
[20], [Zn((2,3-MeO-ba)2en)I2] [16] and [Zn((2,3,4-MeO-ba)2en)I2]
[18]. The Schiff base ligands (3,4-MeO-ba)2en, (2,3-MeO-ba)2en
and (2,3,4-MeO-ba)2en in previous complexes [16,18,20] adopt a
Z,Z configuration around the iminic group, but in this complex, the
Tmax
l
(mmꢀ1
)
Measured reflections
Independent reflections
Reflection with I > 3
r(I)
Rint
S
R[F2 > 2
r
(F2)]
wR(F2)
Parameters
D
D
qmax (e Åꢀ3
qmin (e Åꢀ3
)
)
ꢀ0.62
ꢀ0.65
Crystal size (mm3)
0.36 ꢁ 0.08 ꢁ 0.03
0.41 ꢁ 0.39 ꢁ 0.31

A.D. Khalaji et al. / Polyhedron 49 (2013) 19–23
21
Fig. 1. An ORTEP view of 1 with the atom-numbering scheme. Atomic displacement parameters are shown at the 50% probability level.
Table 2
Selected bond distances (Å) and angles (°) of 1.
I1–Zn1
Zn1–N1
N1–C1
N2–C9
C1–C9
2.5258(7)
2.103(5)
1.478(8)
1.467(8)
1.470(10)
1.488(7)
I2–Zn1
Zn1–N2
N1–C2
N2–C10
C2–C3
2.5460(8)
2.098(4)
1.256(8)
1.249(7)
1.474(8)
C10–C11
I1–Zn1–I2
I1–Zn1–N1
I1–Zn1–N2
Zn1–N1–C1
Zn1–N2–C9
N1–C1–C9
N2–C9–C1
120.69(3)
112.22(13)
115.11(13)
107.3(4)
109.9(4)
108.8(5)
N1–Zn1–N2
N1–Zn1–I2
N2–Zn1–I2
Zn1–N1–C2
Zn1–N2–C10
N1–C2–C3
81.07(17)
114.03(13)
106.93(12)
133.3(4)
129.1(4)
122.5(5)
108.0(5)
N2–C10–C11
126.3(5)
Table 3
Inter-molecular hydrogen bond geometry for 1.
C1–H (Å)
0.960
Hꢂ ꢂ ꢂI1 (Å)
3.135
C1ꢂ ꢂ ꢂI1 (Å)
4.041
C1–Hꢂ ꢂ ꢂI1 (°)
157.847
I1 (x, 0.5 ꢀ y, 0.5 + z).
Schiff base ligand (2,6-Cl-ba)2en adopts a Z,E configuration around
the iminic group (Fig. 1).
The geometry of the hydrogen bonds in 1 is given in Table 3.
Complex 1 exhibits one hydrogen bonding pattern built up from
non-classical C–Hꢂ ꢂ ꢂI interactions (Fig. 2).
3.3. Crystal and molecular structure of 2
An ORTEP view of 2 with the atom-numbering scheme is pre-
sented in Fig. 3. Selected bond distances and angles are given in Ta-
ble 4. The single crystal X-ray analysis has revealed that the
mercury(II) complex [Hg((2,6-Cl-ba)2en)Br2] (2) is neutral and
Fig. 2. Non-classical C–Hꢂ ꢂ ꢂI hydrogen bond in complex 1 (dashed lines).
restricting bite chelate angle N1–Zn1–N2 81.07(17)°, N1–Hg1–N2
70.43(13)° and N3–Hg2–N4 71.13(13)° of the Schiff-base ligand.
For ethylenediamine chelate compounds [16–20] this angle ranges
between 82° and 89°, i.e. significantly below 109.5°. On the con-
trary the I1–Zn1–I2, Br1–Hg1–Br2 and Br3–Hg2–Br4 angle has
opened up to 120.69(3)°, 138.121(16)° and 128.645(16)°, respec-
tively. The N–Zn–I angles are also distorted from the tetrahedral
values (Table 2 for 1 and Table 3 for 2). The Zn1–N1, Zn1–N2,
Hg1–N1, Hg1–N2, Hg2–N3 and Hg2–N4 bond lengths of 2.103(5),
2.098(4), 2.507(4), 2.462(3), 2.540(6) and 2.368(4) Å and Zn1–I1,
Zn1–I2, Hg1–Br1, Hg1–Br2, Hg2–Br3 and Hg2–Br4 bond lengths
of 2.5258(7), 2.5460(8), 2.5067(5), 2.4615(5), 2.5401(5) and
ꢀ
crystallizes in triclinic space group P1. Mercury(II) is coordinated
by two iminic nitrogen atoms of the chelating bidentate Schiff-base
ligand (2,6-Cl-ba)2en and two bromine atoms in a form of strongly
deformed tetrahedron. The geometry around the mercury(II) cen-
ter of this complex is quite similar to the mercury(II) complexes
[Hg((2,3-MeO-ba)2en)Br2] [19] and [Hg((Me-ca)2en)Br2] [17]. The
Schiff base ligands (2,3-MeO-ba)2en and (Me-ca)2en in previous
complexes [17,19] and (2,6-Cl-ba)2en in this complex adopt a Z,Z
configuration around the iminic group (Fig. 3).
Although a tetrahedral geometry might be expected for four
coordinated zinc(II) and mercury(II) centers, it is distorted by the

22
A.D. Khalaji et al. / Polyhedron 49 (2013) 19–23
Fig. 3. An ORTEP view of 2 with the atom-numbering scheme. Atomic displacement parameters are shown at the 50% probability level.
Table 4
P204/11/0809 of the Grant Agency of the Czech Republic for sup-
porting the crystallographic part.
Selected bond distances (Å) and angles (°) of 2.
Hg1–Br1
Hg2–Br3
Hg1–N1
Hg2–N3
N1–C10
N2–C3
N3–C26
N4–C18
C3–C4
2.5067(5)
2.5401(5)
2.507(4)
2.540(6)
1.259(6)
1.267(6)
1.260(6)
1.464(5)
1.466(5)
1.520(7)
1.483(7)
Hg1–Br2
Hg2–Br4
Hg1–N2
Hg2–N4
N1–C1
2.4615(5)
2.4578(5)
2.462(3)
2.368(4)
1.467(6)
1.458(5)
1.469(6)
1.266(6)
1.482(6)
1.516(7)
1.474(5)
Appendix A. Supplementary data
CCDC 902030 and 902031 contain the supplementary crystallo-
graphic data for 1 and 2. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
N2–C2
N3–C17
N4–C19
C10–C11
C17–C18
C19–C20
C1–C2
C26–C27
N1–Hg1–N2
Br1–Hg1–Br2
Br1–Hg1–N1
Br1–Hg1–N2
Br2–Hg1–N1
Br2–Hg1–N2
Hg1–N2–C3
Hg1–N1–C10
N2–C3–C4
70.43(13)
138.121(16)
93.60(5)
100.57(5)
119.87(4)
113.38(5)
132.15(5)
126.21(10)
123.5(4)
N3–Hg2–N4
Br3–Hg2–Br4
Br3–Hg2–N3
Br3–Hg2–N4
Br4–Hg2–N3
Br4–Hg2–N4
Hg2–N4–C19
Hg2–N3–C26
N4–C19–C20
N4–C18–C17
N3–C26–C27
N3–C17–C18
71.13(13)
128.645(16)
95.98(5)
96.18(7)
124.56(5)
124.07(7)
132.0(3)
126.23(5)
121.5(4)
107.4(3)
121.5(4)
110.0(3)
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about the metal centers in these complexes is also approximately
tetrahedral, with the distortion indicated by the unequal metal–li-
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