Structural and solution studies of two mercury(II) complexes with [1,3-bis(2-ethoxy)benzene]triazene

Article abstract of DOI:10.1002/zaac.201100350

The reaction of [1, 3-bis(2-ethoxy)benzene]triazene, [HL], with Hg(SCN)₂ and Hg(CH₃COO)₂, resulted in the formation of the complexes [HgL(SCN)] (1) and [HgL₂]·CH ₃OH (2). They were characterized by means of X-ray crystallography, CHN analysis, FT-IR, ¹H NMR, and ¹³C NMR spectroscopy. The structure of compound 1 consists of two independent complexes in which the Hg^II atoms are stacked along the crystallographic a axis to form infinite chains. Each Hg^II atom is chelated by one L ligand and one SCN ligand, whereas in compound 2, the Hg^II atom is surrounded by two L ligands. In addition, 1D chains formed by metal-π interactions are connected to each other by C-H...π stacking interactions in the structure of 1, which results in a 2D architecture. An interesting feature of compound 2 is the presence of C-H...π edge-to-face interactions. Copyright

Full text of DOI:10.1002/zaac.201100350

ARTICLE
DOI: 10.1002/zaac.201100350
Structural and Solution Studies of two Mercury(II) Complexes with [1,3-
Bis(2-ethoxy)benzene]triazene
Mohammad Kazem Rofouei,*[a] Jafar Attar Gharamaleki,[a] Ehsan Fereyduni,[b]
Aboulfazl Aghaei,[a] Giuseppe Bruno,[c] and Hadi Amiri Rudbari[c]
Keywords: Mercury; Triazene; X-ray diffraction; Solution studies; C–H···π interaction
Abstract. The reaction of [1,3-bis(2-ethoxy)benzene]triazene, [HL], HgII atom is chelated by one L ligand and one SCN ligand, whereas
with Hg(SCN)2 and Hg(CH3COO)2, resulted in the formation of the in compound 2, the HgII atom is surrounded by two L ligands. In
complexes [HgL(SCN)] (1) and [HgL2]·CH3OH (2). They were char-
acterized by means of X-ray crystallography, CHN analysis, FT-IR, 1H
NMR, and 13C NMR spectroscopy. The structure of compound 1 con-
addition, 1D chains formed by metal–π interactions are connected to
each other by C–H···π stacking interactions in the structure of 1, which
results in a 2D architecture. An interesting feature of compound 2 is
sists of two independent complexes in which the HgII atoms are the presence of C–H···π edge-to-face interactions.
stacked along the crystallographic a axis to form infinite chains. Each
two HgII complexes [HgL(SCN)] (1) and [HgL2]·CH3OH (2)
{HL [1,3-bis(2-ethoxy)benzene]triazene} with
Hg(CH3COO)2 and Hg(SCN)2 in methanol. Scheme 1 presents
the starting materials and the reaction procedures.
Introduction
=
The study of transition-metal complexes containing 1,3-di-
aryltriazenide ligands has greatly increased in the past few
years because of the versatility of their coordination forms,
which yielded various coordination compounds with a large
structural diversity. The coordination modes can be mono-
dentate, (N1, N3)-chelating towards one metal atom or (N1,
N3)-bridging over two metal atoms,[1] showing remarkable
ability to support the stereochemical requisites of a wide vari-
ety of transition metal complexes.[2,3] In these compounds sec-
ondary bonds or interactions such as hydrogen bonds and
metal π-aryl interactions can play an important role to stabilize
their structures.[4,5] We have previously reported the synthesis
of the ligands 1,3-bis(2-methoxyphenyl)]triazene,[6] [1,3-bis(2-
ethoxyphenyl)]triazene,[7] and [1,3-bis(2-cyanophenyl)]triaz-
ene[8]. Additionally, we have published HgII complexes with
[9]
[1,3-bis(2-methoxyphenyl)]triazene by using HgCl2
and
[10]
HgBr2
as starting materials. In addition, AgI and CdII com-
plexes with this ligand are known.[11,12] More recently, a HgII
complex with [1,3-bis(2-ethoxyphenyl)]triazene as ligand has
been reported, in which HgCl2 was used as starting salt.[13]
In continuation of our previous work, we herein report the
syntheses, characterizations and molecular structures of the
Scheme 1.
* Prof. Dr. M. K. Rofouei
Fax: +98-2188820993.
Experimental Section
E-Mail: rofouei_mk@yahoo.com
[a] Faculty of Chemistry
Tarbiat Moallem University
Tehran, Iran
Materials and Physical Techniques: All chemicals were of analytical
grade and were used as commercially obtained without further purifi-
cation. IR spectra in the frequency range of 4000–400 cm–1 were re-
corded with a Perkin–Elmer RXI spectrometer using KBr disks. Ele-
mental analysis was carried out with a Perkin–Elmer 2400(II) CHNS/
O analyzer. Melting points were measured with a Barnstead Electro-
thermal 9200 apparatus. UV-Vis spectra were recorded with a Perkin–
Elmer Lambda 25 spectrophotometer, using two matched 10 mm
[b] Department of Chemistry
Tabriz Branch, Islamic Azad University
Tabriz, Iran
[c] Dipartimento di Chimica Inorganica
Universita di Messina
Messina, Italy
220
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 638, (1), 220–223

Mercury(II) Complexes with [1,3-Bis(2-ethoxy)benzene]triazene
quartz cells. Crystallographic measurements were made with a Bruker benzene]triazene (0.286 g, 1 mmol) in anhydrous methanol (40 mL),
APEX2 CCD area detector diffractometer. The intensity data were col-
lected using graphite monochromated Mo-Kα radiation (λ
0.71073 Å). The structure has been solved by direct methods and re-
mercury(II) acetate (0.1583 g, 0.5 mmol) dissolved in anhydrous meth-
anol (5 mL) was added. After stirring for 0.5 h, an orange precipitate
was formed. It was filtered off, washed with methanol, and dried in
=
fined by full-matrix least-squares techniques on F2 using vacuo. The solid was dissolved in THF (20 mL). Air stable, orange-
SHELXTL.[14] The molecular structure plots were prepared using red plate like crystals of complex 2 suitable for X-ray analysis were
PLATON[15] and MERCURY.[16] The details of data collection, refine-
ment, and crystal data are summarized in Table 1.
obtained by slow evaporation of the solvent within a week. M.p.: 146–
148 °C. IR (KBr): ν˜ = 3067 (C–H, sp2), 2974 (C–H, sp3), 2925 (C–
H, sp3), 1587 (C=C), 1492 (N=N), 1394 (C–O), 1039 (C–O), 742 (or-
Synthesis of [HgII(RPhNNNPhR)SCN] (R = OC2H5), [HgL(SCN)],
(1): The ligand [1,3-bis(2-ethoxy)benzene]triazene was prepared ac-
cording to a method described earlier.[7] The complex was prepared
by mixing [1,3-bis(2-ethoxy)benzene]triazene (0.285 g, 1 mmol) in an-
hydrous methanol (20 mL) with mercury(II) thiocyanate (0.316 g,
1 mmol) in anhydrous methanol (20 mL). After stirring for 1 h, a pre-
cipitate was obtained, which was filtered off and washed. Afterwards,
1
tho subst. Ph) cm–1. H NMR (300 MHz, [D6]DMSO): δ = 1.04 (8 H,
CH2), 1.75 (12 H, CH3), 6.92–7.66 (16 H, aromatic) ppm. 13C NMR
(300 MHz, DMSO): δ = 14.1, 14.8, 64.4, 113.6–148.9 ppm. Elemental
analysis C33H40HgN6O5 (801.3): C 49.46; H 5.03; N 10.49%; found:
C 49.72; H 4.95; N 10.39%.
it was dissolved in THF. Air stable, yellow needle-like crystals of com- Results and Discussion
plex 1 suitable for X-ray analysis were obtained by slow evaporation
of the solvent in two weeks. M.p.: 144–145 °C. IR (KBr): ν˜ = 3066
(C–H, sp2), 2983 (C–H, sp3), 2932 (C–H, sp3), 2137 (CϵN), 1586
(C=C), 1494 (N=N), 1396 (C–O), 1038 (C–O), 755 (ortho subst. Ph)
cm–1. The appearance of strong υas(S–CϵN) absorption at 2137 cm–1
is consistent with the presence of S-terminal thiocyanato ions,[17]
which is in agreement with the X-ray diffraction studies. 1H NMR
(300 MHz, [D6]DMSO): δ = 1.04 (4 H, CH2), 1.46 (6 H, CH3), 6.90–
7.65 (8 H, aromatic) ppm. 13C NMR (300 MHz, DMSO): δ = 14.1,
14.8, 64.4, 112.4–148.9 ppm. Elemental analysis C17H18HgN4O2S
(544.0): C 37.60; H 3.34; N 10.32%; found: C 37.59; H 3.30; N
10.34%.
Molecular Structures of Complexes 1 and 2
The molecular structure of [HgII(RPhNNNPhR)SCN] (R =
OC2H5), [HgL(SCN)] (1), is presented in Figure 1. Crystal
data for complex 1 is given in Table 1. Selected bond lengths
are listed in Table 2. The unit cell of 1 consists of two indepen-
dent HgII complexes with slightly different bond lengths and
angles. In both fragments, the HgII atoms are coordinated in a
planar fashion by one triazenide ion and one thiocyanate ion
(through sulfur atom). In the lattice of this compound (Fig-
ure 2), the molecules are stacked along the crystallographic a
axis to form infinite chains. Within the chains, each HgII atom
Synthesis of [HgII (RPhNNNPhR)2] (R = OC2H5), [HgL2].CH3OH,
(2): To a yellow solution prepared by dissolving [1,3-bis(2-ethoxy) is additionally coordinated by two peripheral phenyl rings of
Table 1. Crystal data for compounds 1 and 2.
1
2
Empirical formula
Formula weight
Temperature
C17H18HgN4O2S
544.00
293(2)
C32H36HgN6O4 (CH3OH)
801.30
293(2)
Wavelength
Crystal system
Space group
0.71073
0.71073
triclinic
P1
triclinic
¯
¯
P1
Unit cell dimensions /Å, °
a = 11.0082(2)
α = 101.3330(10)
b = 11.7364(3)
β = 100.7160(10)
c = 15.2112(3)
γ = 103.1680(10)
1820.64(7)
a = 12.2409(3)
α = 87.0740(10)
b = 12.4679(3)
β = 70.1190(10)
c = 13.0150(3)
γ = 67.7680(10)
1722.19(7)
Volume /Å3
Z
4
2
Density (calculated) /Mg·m–3
Absorption coefficient /mm–1
F(000)
1.985
8.59
1044
1.545
4.52
800
θ Range for data collection /deg
Index ranges
1.4 to 27.6
2.5 to 29.5
–14 Յ h Յ 14
–14 Յ k Յ 14
–19 Յ l Յ 19
–15 Յ h Յ 15
–15 Յ k Յ 15
–16 Յ l Յ 16
Reflections collected / unique
Absorption correction
Refinement method
111621/7878, [R(int) = 0.0350]
multi-scan, Sheldrick, G. M. (2004)
Full-matrix least-squares on F2
7878 / 0 / 470
159203/7512, [R(int) = 0.0295]
multi-scan, Sheldrick, G. M. (2004)
Full-matrix least-squares on F2
7512 / 0 / 434
1.06
Data/restraints/parameters
Goodness-of-fit on F2
1.098
Final R[I Ͼ 2σ(I)]
R1 = 0.0306 wR2 = 0.0768
R1 = 0.0389, wR2 = 0.0820
1.68 and –1.05
R1 = 0.0501, wR2 = 0.1378
R1 = 0.0614, wR2 = 0.1555
1.02 and –1.49
R indices (all data)
Largest differences in peak and hole /e·A–3
Z. Anorg. Allg. Chem. 2012, 220–223
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
221

M. K. Rofouei et al.
ARTICLE
two neighboring complexes by secondary weak metal–π inter-
actions. The two phenyl rings are located parallel to the main
molecular plane. These metal–π interactions involve the Cg1
[3.565(13) Å] and Cg2 [3.481(13) Å] with related symmetry
code (1–x, 1–y, 1–z) and (2–x, 1–y, 1–z), respectively. Also,
weak intermolecular metal–π interactions with Cg3
[3.459(13) Å] and Cg4 [3.490(13) Å] with related symmetry
code (–x, 2–y, –z) and (1–x, 2–y, –z) are present. Cg1, Cg2,
Cg3, and Cg4 are the centers of (C3A–C8A), (C9A–C14A),
(C3B–C8B), and (C9B–C14B) rings, respectively. Conse-
quently, 1D chains, formed by metal–π interactions, are con-
nected with one another by C–H···π stacking interactions, re-
sulting in a 2D architecture. These C–H···π stacking interac-
tions are present between CH groups with aromatic rings with
H···π distances of 2.85 Å for C5A–H5A···Cg4 (1–x, 2–y, 1–z),
2.93 Å for C13A–H13A···Cg3 (1–x, 1–y, –z) and 2.88 Å for
C15B–H15C···Cg2 (x, 1+y, z).[18]
Figure 2. View of the supramolecular network formed by Hg–π inter-
actions in 1.
which exist between CH groups of phenyl rings (Figure 4).
Additionally, the sum of the weak non-covalent interactions
seems to play an important role in the crystal packing and the
formation of the framework.
Figure 1. ORTEP diagram of the structural unit of 1 with the atomic
numbering scheme. Thermal ellipsoids are drawn at 50% probability
level.
Table 2. Selected bond lengths /Å for compounds 1 and 2.
1
Hg1A–O1A
Hg1A–N1A
Hg1A–N3A
Hg1A–S1A
Hg2A–O2A
Hg2A–N1A
Hg2A–N3A
Hg2A–S1A
2.864(3)
2.129(3)
2.566(3)
2.3422(12)
2.851(2)
2.552(3)
2.119(3)
2.3398(12)
Hg1B–O1B
Hg1B–N1B
Hg1B–N3B
Hg1B–S1B
Hg2B–O2B
Hg2B–N1B
Hg2B–N3B
Hg2B–S1B
2.962(3)
2.147(3)
2.521(3)
2.3553(12)
2.813(3)
2.559(3)
2.102(3)
2.3315(11)
Figure 3. ORTEP diagram of the structural unit of 2 with the atomic
numbering scheme. Thermal ellipsoids are drawn at 50% probability
level. Methanol molecule is not shown for clarity.
2
Hg1–N3Ј
Hg1–N1
Hg1Ј–N1Ј
Hg1Ј–N3
2.120(3)
2.127(3)
2.087(3)
2.136(3)
Hg2–N1Ј
Hg2–N1
Hg2Ј–N3
Hg2Ј–N3Ј
2.132(3)
2.137(3)
2.121(3)
2.157(3)
The molecular structure of the complex [HgL2]·CH3OH (2)
is shown in Figure 3. Crystal data for complex 2 is given in
Table 1. The HgII atom is coordinated by two symmetrically
independent triazenide ions. Each triazenide ion is coordinated
to the central metal atom through nitrogen and oxygen atoms,
with relatively weak Hg–O bonds. Hg–O and Hg–N interac-
tions with longer bond lengths were reported.[19] An interesting
Figure 4. C–H···π stacking interactions between two [HgL2] moieties
feature of compound 2 is the presence of C–H···π interactions, in compound 2.
222 www.zaac.wiley-vch.de
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 220–223

Mercury(II) Complexes with [1,3-Bis(2-ethoxy)benzene]triazene
Solution Studies
sorbance (at 373 nm) against [Hg2+]/[HL] mole ratio plot,
which is shown in the inset of Figure 5, reveals a distinct inec-
tion point at a metal-to-ligand molar ratio of about 1 emphasiz-
ing the formation of a 1:1 complex in MeOH solution. The
resulting absorbance (at 397 nm) against [Hg2+]/[HL] mole ra-
tio plot, which is shown in the inset of Figure 6, reveals dis-
tinct inection points at a metal-to-ligand molar ratio of about
0.5 and 1 emphasizing the formation of 1:2 and 1:1 complexes.
It seems that these compounds have different behavior in the
solid state and in solution.
In a typical procedure, a solution of the ligand (2.0 mL,
5.0ϫ10–5 M) in MeOH was placed in the spectrophotometer
cell and the absorbance was measured. Afterwards, a known
amount of a concentrated solution of HgII thiocyanate or acet-
ate in MeOH (2.5ϫ10–3 M) was added stepwise using a 10 μL
Hamilton syringe. The absorbance spectrum of the mixture
was recorded after each addition. The mercury(II) thiocyanate
or acetate solution was continually added until the desired
metal-to-ligand mole ratio was achieved. The electronic ab-
sorption spectra of the ligand in the presence of increasing HgII
thiocyanate or acetate concentration at room temperature are
shown in Figure 5 and Figure 6, respectively. The resulting ab-
References
[1] D. S. Moore, S. D. Robinson, Adv. Inorg. Chem. Radiochem.
1986, 28, 1.
[2] M. Horner, V. S. Carratu, J. Bordinhao, A. Silva, E. Niquet, Acta
Crystallogr. Sect. C 2004, 60, m140.
[3] M. Horner, A. J. Bortoluzzi, J. Beck, M. Serafin, Z. Anorg. Allg.
Chem. 2002, 628, 1104.
[4] K. Vrieze, G. Van Koten, Comprehensive Coordination Chemis-
try, Oxford, Pergamon Press, 1987, pp. 189–244, .
[5] M. Horner, G. Manzoni de Oliveira, J. S. Bonini, H. Fenner, J.
Organomet. Chem. 2006, 691, 655.
[6] M. K. Rofouei, M. Shamsipur, M. Payehghadr, Anal. Sci. 2006,
22, x79.
[7] M. K. Rofouei, M. R. Melardi, Y. Salemi, S. R. Kazemi, Acta
Crystallogr. Sect. E 2009, 65, o719.
[8] M. R. Melardi, H. R. Khalili Ghaydari, M. Barkhi, M. K. Rofouei,
Anal. Sci. 2008, 24, x281.
[9] M. R. Melardi, M. K. Rofouei, J. Massomi, Anal. Sci. 2007, 23,
x67.
[10] M. Hematyar, M. K. Rofouei, Anal. Sci. 2008, 24, x117.
[11] M. Payehghadr, M. K. Rofouei, A. Morsali, M. Shamsipur, Inorg.
Chim. Acta 2007, 360, 1792.
Figure 5. (a) Electronic absorption spectra of ligand [HL] in MeOH
(5.0ϫ10–5 M) in the presence of increasing concentration of mer-
cury(II) thiocyanate at room temperature. (b) Correspondingmole ratio
plot at 373 nm.
[12] M. K. Rofouei, M. R. Melardi, H. R. Khalili Ghaydari, M. Barkhi,
Acta Crystallogr. Sect. E 2009, 65, m351.
[13] M. R. Melardi, Y. Salemi, S. Razi Kazemi, M. K. Rofouei, Acta
Crystallogr. Sect. E 2009, 65, m302.
[14] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112.
[15] A. L. Spek, PLATON, A Multipurpose Crystallographic Tool,
Utrecht University, Utrecht, Netherlands, 2005.
[16] Mercury 1.4.1, Copyright Cambridge Crystallographic Data Cen-
tre, 12 Union Road,
[17] R. Bala, R. P. Sarma, R. Sharma, B. M. Kariuki, Inorg. Chem.
Commun. 2006, 9, 852.
[18] X.-P. Li, J.-Y. Zhang, Y. Liu, M. Pan, S.-R. Zheng, B.-S. Kang,
C.-Y. Su, Inorg. Chim. Acta 2007, 360, 2990.
[19] M. K. Rofouei, E. Fereyduni, N. Sohrabi, M. Shamsipur, J. At-
tar Gharamaleki, N. Sundaraganesan, Spectrochim. Acta Part A
2011, 78, 88.
Figure 6. (a) Electronic absorption spectra of ligand [HL] in MeOH
(5.0ϫ10–5 M) in the presence of increasing concentration of mer-
cury(II) acetate at room temperature. (b) Correspondingmole ratio plot
at 397 nm.
Received: July 31, 2011
Published Online: December 5, 2011
Z. Anorg. Allg. Chem. 2012, 220–223
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
223