Reduction of 2,2′-dinitrobiphenyl with hydrazine hydrate catalyzed by Pd/C: Cobalt(II), zinc(II) and mercury(II) complexes with benzo[c]cinnoline and N2,N2′-bis(3-phenylallylidene)biphenyl-2,2′- diamine

Article abstract of DOI:10.1016/j.poly.2011.12.041

The catalytic reduction of 2,2′-dinitrobiphenyl with different molar ratios of hydrazine hydrate resulted in two different compounds; benzo[c]cinnoline (L¹) and 2,2′-diaminobiphenyl. N ²,N^2′-bis(3-phenylallylidene)biphenyl-2,2′- diamine (L²) has been synthesized by the condensation of 2,2′-diaminobiphenyl with cinnamaldehyde. Complexes of the type ML ¹₂X₂ and ML²X₂ (M = Co(II), Zn(II); X = Cl, Br or I and Hg(L²)Cl₂) have been synthesized and characterized by CHN analysis, IR, ¹H NMR and UV-Vis spectroscopy. The crystal structures of Co(L¹)₂Cl ₂, Zn(L¹)₂Br₂ and Hg(L ²)Cl₂ were determined using single crystal X-ray diffraction. In these three complexes, the coordination polyhedron about the central metal ion is best described as a distorted tetrahedron. The Co(L ¹)₂Cl₂, and Zn(L¹) ₂Br₂ complexes exhibit supramolecular structures resulting from π-π stacking of the benzo[c]cinnoline ligands. The diimine ligand, L², in the Hg(L²)Cl₂ complex coordinates to Hg(II) through the two nitrogens of the two phenyl rings to form a seven-membered metallocycle. Furthermore, the ligand prefers a trans-trans arrangement in the Hg(L²)Cl₂ complex.

Full text of DOI:10.1016/j.poly.2011.12.041

Polyhedron 35 (2012) 69–76
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Reduction of 2,20-dinitrobiphenyl with hydrazine hydrate catalyzed by Pd/C:
Cobalt(II), zinc(II) and mercury(II) complexes with benzo[c]cinnoline and
20
N2,N -bis(3-phenylallylidene)biphenyl-2,20-diamine
a
b
Saeed Dehghanpour a, , Farzaneh Afshariazar , Jalil Assoud
⇑
a Department of Chemistry, Alzahra University, P.O. Box 1993891176, Tehran, Iran
b Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
a r t i c l e i n f o
a b s t r a c t
The catalytic reduction of 2,20-dinitrobiphenyl with different molar ratios of hydrazine hydrate resulted in
Article history:
20
two different compounds; benzo[c]cinnoline (L1) and 2,20-diaminobiphenyl. N2,N -bis(3-phenylallylid-
Received 29 November 2011
Accepted 29 December 2011
Available online 17 January 2012
ene)biphenyl-2,20-diamine (L2) has been synthesized by the condensation of 2,20-diaminobiphenyl with
cinnamaldehyde. Complexes of the type ML12X2 and ML2X2 (M = Co(II), Zn(II); X = Cl, Br or I and Hg(L2)Cl2)
have been synthesized and characterized by CHN analysis, IR, 1H NMR and UV–Vis spectroscopy. The
crystal structures of Co(L1)2Cl2, Zn(L1)2Br2 and Hg(L2)Cl2 were determined using single crystal X-ray
diffraction. In these three complexes, the coordination polyhedron about the central metal ion is best
described as a distorted tetrahedron. The Co(L1)2Cl2, and Zn(L1)2Br2 complexes exhibit supramolecular
Keywords:
Catalytic reduction
2,20-Dinitrobiphenyl
Benzo[c]cinnoline
2,20-Diaminobiphenyl
Diimine
structures resulting from
p–p
stacking of the benzo[c]cinnoline ligands. The diimine ligand, L2, in the
Hg(L2)Cl2 complex coordinates to Hg(II) through the two nitrogens of the two phenyl rings to form a
seven-membered metallocycle. Furthermore, the ligand prefers a trans–trans arrangement in the Hg(L2)Cl2
complex.
Complex
Structure
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
benzo[c]cinnoline (L1) and 2,20-diaminobiphenyl (Scheme 1).
20
N2,N -bis(3-phenylallylidene)biphenyl-2,20-diamine has been syn-
Transition metal complexes containing nitrogen donor ligands
are major group of coordination compounds, which play
thesized by the condensation of 2,20-diaminobiphenyl with cinna-
maldehyde (Scheme 1). Also, we wish to report the synthesis and
spectral characterization of some new transition metal complexes
of Co, Zn and Hg with the synthetic ligands. Structural analysis by
X-ray diffraction led to the structural confirmation of these new
complexes.
a
an important role in the development of coordination chemistry.
Recent years have witnessed a great deal of interest in the synthe-
sis of new chelating functions, such as the mono, bi, tri and tetra-
dentate type nitrogen donor ligands, and their corresponding
complexes due to their interesting applications in magnetism,
molecular architectures, enzymatic reactions and especially in
developing new catalytic systems [1–5]. Moreover, nitrogen based
ligands with the metal centers such as zinc and mercury result in
supramolecular architectures, designing of biological models and
fluorescent compounds [6,7]. Altering and modifying the physical
and chemical properties of these systems is easily carried out by
varying the number, size and the nature of the substituents on
the ligands. This paper deals with the synthesis and spectroscopic
characterization of two N-donor ligands, benzo[c]cinnoline (L1)
2. Experimental
2.1. General
All reagents were purchased from commercial sources (Aldrich/
Merck) and were used as received without further purification.
Solvents used for the reactions were purified and dried by conven-
tional methods [8]. Infrared spectra were recorded as KBr pellets
on a Bruker Tensor 27 instrument. NMR spectra were obtained
on Bruker AC-250 MHz and AC-500 MHz spectrometers. Proton
chemical shifts are reported in part per million (ppm) relative to
tetramethylsilane as an internal standard. Electronic absorption
spectra were recorded on a JASCO V-570 spectrophotometer, and
20
and N2,N -bis(3-phenylallylidene)biphenyl-2,20-diamine (L2). The
catalytic reduction of 2,20-dinitrobiphenyl by changing the molar
ratio of the reductant (hydrazine) results in the two products
⇑
the results are given as kmax (log
formed using a Heraeus CHN-O-RAPID elemental analyzer.
e). Elemental analyses were per-
Corresponding author. Tel./fax: +98 21 88041344.
E-mail address: dehganpour_farasha@yahoo.com (S. Dehghanpour).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.12.041

70
S. Dehghanpour et al. / Polyhedron 35 (2012) 69–76
Hc
Hd
Hb
4N2H4
Ha
N
N
NO2
NH2
N
O2N
10
N2H4
trans-cinnamaldehyde
H2N
N
Scheme 1. Catalytic reduction of 2,20-dinitrobiphenyl with different molar ratios of hydrazine hydrate.
2.2. Syntheses
m(C@N). 1H NMR (500 MHz, CDCl3) d: 6.89–6.99 (m, 6H, 2-C@CH–C–,
4-ortho H of ArH), 7.31–7.45 (m, 16H, 2PhCH@C–, ArH), 8.09 (d, 2H,
3JHH = 5 Hz, 2-CH@N–). UV–Vis (CHCl3, nm): 340(4.41), 295(4.75).
Anal. Calc. for C30H24N2: C, 87.35; H, 5.86; N, 6.79. Found: C,
87.40; H, 5.80; N, 6.83%.
2.2.1. Benzo[c]cinnoline (L1)
To a solution of 2,20-dinitrobiphenyl (1 g, 4 mmol) in hot ethanol
(15 ml) was added 100 mg 10% Pd/C as a catalyst. About 1.0 ml of
80% hydrazine hydrate (16 mmol) was added dropwise (every
15 min) and the reaction mixture was refluxed for 4 h. After 4 h,
the heating was stopped and the catalyst was immediately filtered
off. By cooling the yellow filtrate to room temperature, yellow crys-
tals appeared in the solution, which were recrystallized in cold eth-
2.2.4. Co(L1)2Cl2 (1a)
To a solution of anhydrous CoCl2 (50 mg, 0.385 mmol) in 5 ml
acetonitrile was added a solution of L1 (139 mg, 0.77 mmol) in
5 ml acetonitrile, and the mixture was stirred at room temperature
for 3 h. On slow evaporation of the solution, blue crystals were
obtained, which were collected by filtration, washed with a mixture
of diethylether–acetonitrile (9:1, v/v) and dried under vacuum.
anol. Mp 154–156 °C. Yield: 85%. IR (KBr, cmꢀ1): 1463
m(N@N). 1H
NMR (250 MHz, CDCl3) d: 7.67–8.03 (m, 4H, Hb, Hc), 8.36–8.87 (m,
4H, Ha, Hd). UV–Vis (CHCl3, nm): 384(3.75), 365(3.85), 333(3.97),
313(3.91), 296(4.05), 263(4.44), 254(4.70). Anal. Calc. for C12H8N2:
C, 79.98; H, 4.47; N, 15.54. Found: C, 80.05; H, 4.41; N, 15.49%.
Yield: 85%. IR (KBr, cmꢀ1): 1455
m(N@N). UV–Vis (CHCl3, nm):
678(2.05), 635(1.88), 615(1.86), 367(3.44), 353(3.54), 312(4.27),
303(4.26), 256(5.27). Anal. Calc. for C24H16Cl2CoN4: C, 58.80; H,
3.29; N, 11.43. Found: C, 58.86; H, 3.34; N, 11.49%.
2.2.2. 2,20-Diaminobiphenyl
To a solution of 2,20-dinitrobiphenyl (1 g, 4 mmol) in hot ethanol
(15 ml) was added 100 mg 10% Pd/C as a catalyst. About 2.5 ml of
80% hydrazine hydrate (40 mmol) was added dropwise sequen-
tially (every 15 min). The reaction mixture was then refluxed for
6 h to complete the reduction (reduction was complete when the
solution had become completely colorless). After 6 h, the heating
was stopped and the catalyst was immediately filtered off. The
volume of the solution was reduced to half of its original volume
by heating and then water was added to the filtrate. On adding
water, the solution became cloudy and colorless crystals appear
in the solution after 30 min. Mp 78–79 °C. Yield: 90%. IR (KBr
2.2.5. Co(L1)2Br2 (2a)
This complex was synthesized by a procedure similar to that for
1a using anhydrous CoBr2 (50 mg, 0.23 mmol). Yield: 65%. IR (KBr,
cmꢀ1): 1453
m(N@N). UV–Vis (CHCl3, nm): 682(2.10), 639(1.90),
619(1.81), 369(3.42), 350(3.56), 315(4.25), 306(4.21), 259(5.30).
Anal. Calc. for C24H16Br2CoN4: C, 49.77; H, 2.78; N, 9.67. Found:
C, 49.83; H, 2.81; N, 9.60%.
2.2.6. Co(L1)2I2 (3a)
This complex was synthesized by a procedure similar to that for
1a using anhydrous CoI2 (50 mg, 0.16 mmol). Yield: 69%. IR (KBr,
cmꢀ1): 3384, 3401
m(N–H). 1H NMR (250 MHz, CDCl3) d: 3.69 (s,
cmꢀ1): 1450
m(N@N). UV–Vis (CHCl3, nm): 685(2.09), 638(1.85),
4H, 2-NH2), 6.75–6.85 (m, 4H, Hb, Hc), 7.09–7.24 (m, 4H, Ha, Hd).
UV–Vis (CHCl3, nm): 359(1.79), 299(3.49), 256(3.71). Anal. Calc.
for C12H12N2: C, 78.23; H, 6.57; N, 15.20. Found: C, 78.30; H, 6.62;
N, 15.25%.
622(1.78), 368(3.40), 345(3.55), 316(4.23), 310(4.25), 260(5.31).
Anal. Calc. for C24H16CoI2N4: C, 42.82; H, 2.40; N, 8.32. Found: C,
42.87; H, 2.35; N, 8.39%.
20
2.2.3. N2,N -bis(3-phenylallylidene)biphenyl-2,20-diamine (L2)
2.2.7. Zn(L1)2Cl2 (4a)
To a solution of 2,20-diaminobiphenyl (1 g, 5 mmol) in ethanol
(15 ml) was added a solution of trans-cinnamaldehyde (1.634 g,
10 mmol) in ethanol (2 ml) and the resulting mixture was stirred
at room temperature for 1 h. The ligand (L2) was obtained as a
yellow microcrystalline precipitate. It was then filtered off, washed
with cold diethylether and dried in air. Yield: 90%. IR (KBr): 1624 cmꢀ1
To a solution of ZnCl2 (50 mg, 0.367 mmol) in acetonitrile (5 ml)
was added a solution of L1 (132 mg, 0.733 mmol) in acetonitrile
(5 ml), and the mixture was stirred for 1 h. On slow evaporation
of the solution, yellow crystals were obtained, collected by filtra-
tion, washed with a mixture of diethylether–acetonitrile (9:1, v/
v) and dried under vaccum. Yield: 90%. IR (KBr, cmꢀ1): 1454
m

S. Dehghanpour et al. / Polyhedron 35 (2012) 69–76
71
3
(N@N). 1H NMR (500 MHz, DMSO-d6) d: 7.09–8.07 (m, 4H, Hb, Hc),
8.67–8.69 (m, 2H, Hd), 8.87–8.90 (m, 2H, Ha). UV–Vis (CHCl3, nm):
394(2.83), 368(3.35), 353(3.45), 340(3.36), 312(4.19), 303(4.18),
259(4.65). Anal. Calc. for C24H16Cl2N4Zn: C, 58.03; H, 3.25; N,
11.28. Found: C, 58.10; H, 3.30; N, 11.24%.
22H, 2PhCH@C–, 2-C@CH–C–, ArH), 8.14 (d, 2H, JHH = 8.50 Hz, 2-
CH@N–). UV–Vis (DMSO, nm): 371(3.86), 342(4.14), 298(4.69).
Anal. Calc. for C30H24Br2N2Zn: C, 56.50; H, 3.79; N, 4.39. Found:
C, 56.58; H, 3.84; N, 4.43%.
2.2.15. Zn(L2)I2 (6b)
2.2.8. Zn(L1)2Br2 (5a)
This complex was synthesized by a procedure similar to that for
4b using ZnI2 (0.05 g, 0.157 mmol). Yield: 95%. IR (KBr, cmꢀ1): 1576
This complex was synthesized by a procedure similar to that for
4a using ZnBr2 (50 mg, 0.222 mmol). Yield: 95%. IR (KBr, cmꢀ1):
m
(C@N). 1H NMR (250 MHz, DMSO-d6) d: 6.84–7.44 (m, 22H,
3
1454 m(N@N). 1H NMR (500 MHz, DMSO-d6) d: 8.03–8.09 (m, 4H,
2PhCH@C–, 2-C@CH–C–, ArH), 8.11 (d, 2H, JHH = 8.75 Hz, 2-
CH@N–). UV–Vis (DMSO, nm): 370(3.89), 344(4.26), 294(4.78).
Anal. Calc. for C30H24I2N2Zn: C, 49.24; H, 3.31; N, 3.83. Found: C,
49.29; H, 3.32; N, 3.78%.
Hb, Hc), 8.71–8.73 (m, 2H, Hd), 8.93–8.94 (m, 2H, Ha). UV–Vis
(CHCl3, nm): 392(2.49), 369(2.98), 354(3.07), 343(2.98),
313(3.98), 303(3.97), 259(4.76). Anal. Calc. for C24H16Br2N4Zn: C,
49.22; H, 2.75; N, 9.57. Found: C, 49.28; H, 2.79; N, 9.51%.
2.2.16. Hg(L2)Cl2 (7b)
2.2.9. Zn(L1)2I2 (6a)
This complex was synthesized by a procedure similar to that for
4b using HgCl2 (50 mg, 0.184 mmol) in methanol. Yield: 90%. IR
This complex was synthesized by a procedure similar to that for
4a using ZnI2 (50 mg, 0.157 mmol). Yield: 85%. IR (KBr, cmꢀ1): 1453
(KBr, cmꢀ1): 1583
2H, JHH = 15.75 Hz, JHH = 9.50 Hz, 2-C@CH–C–), 6.99–7.77 (m,
m
(C@N). 1H NMR (250 MHz, CDCl3) d: 6.39 (dd,
m
(N@N). 1H NMR (500 MHz, DMSO-d6) d: 8.03–8.10 (m, 4H, Hb, Hc),
3
3
8.71–8.73 (m, 2H, Hd), 8.93-–8.95 (m, 2H, Ha). UV–Vis (CHCl3, nm):
391(2.92), 368(3.42), 353(3.53), 340(3.44), 312(3.96), 303(3.95),
259(4.49). Anal. Calc. for C24H16I2N4Zn: C, 42.42; H, 2.37; N, 8.24.
Found: C, 42.49; H, 2.31; N, 8.30%.
3
20H, 2PhCH@C–, ArH), 8.14 (d, 2H, JHH = 9.50 Hz, 2-CH@N–).
UV–Vis (CHCl3, nm): 365(2.76), 290(4.19), 241(3.91). Anal. Calc.
for C30H24Cl2HgN2: C, 52.68; H, 3.54; N, 4.10. Found: C, 52.76; H,
3.61; N, 4.14%.
2.2.10. Co(L2)Cl2 (1b)
2.3. X-ray analyses
To a solution of anhydrous CoCl2 (50 mg, 0.385 mmol) in aceto-
nitrile (10 ml) was added a solution of L2 (159 mg, 0.385 mmol) in
acetonitrile (10 ml), and the reaction mixture was stirred for 1 h.
On slow evaporation of the solution, blue crystals formed, which
were collected by filtration, washed with a mixture of diethyl-
ether–acetonitrile (9:1, v/v) and dried under vacuum. Yield:
Crystals of 1a, 5a and 7b which were suitable for X-ray crystal-
lography were obtained as described above. A summary of the key
crystallographic information is given in Table 1. Diffraction data for
1a were collected on a Bruker SMART 1000 CCD diffractometer
using graphite-monochromated MoK
a radiation (k = 0.71073 Å).
85%. IR (KBr, cmꢀ1): 1575
644(2.64), 621(2.79), 584(2.84), 391(3.67), 330(4.58). Anal. Calc.
for C30H24Cl2CoN2: C, 66.44; H, 4.46; N, 5.17. Found: C, 66.49; H,
4.40; N, 5.23%.
m(C@N). UV–Vis (CHCl3): 677(2.39),
The raw frame data were processed using SAINT [9]. An empirical
absorption correction was applied using SADABS [10] and the struc-
ture was solved using direct methods and refined by the full-
matrix least-squares method on F2 data using SHELXTL [11]. All H
atoms were positioned geometrically and refined using a riding
model with d(C–H) = 0.93 Å, Uiso = 1.2Ueq (C). Diffraction data for
5a were collected on a Bruker SMART APEX2 CCD area detector
2.2.11. Co(L2)Br2 (2b)
This complex was synthesized by a procedure similar to that for
1b using anhydrous CoBr2 (50 mg, 0.23 mmol). Yield: 69%. IR (KBr,
using graphite monochromated MoK
a radiation (k = 0.71073 Å).
cmꢀ1): 1572
m(C@N). UV–Vis (CHCl3, nm): 682(3.20), 654(3.05),
Preliminary orientation matrices were obtained from the first
frames using APEX2 [12]. An empirical absorption correction was
applied using SADABS [10]. The structure was solved using direct
methods and refined by the full-matrix least-squares method on
F2 data using SHELXTL [11]. All H atoms were positioned geometri-
cally and refined using a riding model with d(C–H) = 0.93 Å,
Uiso = 1.2Ueq (C). Diffraction measurements for 7b in oil were
631(2.79), 409(3.76), 323(4.41). Anal. Calc. for C30H24Br2CoN2: C,
57.08; H, 3.83; N, 4.44. Found: C, 57.12; H, 3.89; N, 4.46%.
2.2.12. Co(L2)I2 (3b)
This complex was synthesized by a procedure similar to that for
1b using anhydrous CoI2 (50 mg, 0.16 mmol). Yield: 76%. IR (KBr,
cmꢀ1): 1576
m(C@N). UV–Vis (CHCl3, nm): 698(3.14), 677(3.01),
recorded on a Bruker Apex CCD diffractometer fitted with MoK
a
636(2.82), 409(3.80), 327(4.70). Anal. Calc. for C30H24CoI2N2: C,
49.68; H, 3.34; N, 3.86. Found: C, 49.72; H, 3.39; N, 3.92%.
radiation. The raw frame data were processed using SAINT [13]
and SADABS [14] to yield the reflection data file. The structure was
solved with direct methods and refined with full-matrix least-
squares procedures (SHELXTL) [11] with anisotropic thermal param-
eters for all non-hydrogen atoms.
2.2.13. Zn(L2)Cl2 (4b)
To a solution of ZnCl2 (50 mg, 0.367 mmol) in acetonitrile
(10 ml) was added a solution of L2 (151 mg, 0.367 mmol) in aceto-
nitrile (10 ml). On slow evaporation of the solvent, yellow crystals
appeared, which were collected by filtration, washed with a
mixture of diethylether–acetonitrile (9:1 v/v) and dried under
3. Results and discussions
vacuum. Yield: 92%. IR (KBr, cmꢀ1): 1579
m(C@N). 1H NMR
3.1. Synthesis and spectral properties
(250 MHz, DMSO-d6) d: 6.87–7.44 (m, 22H, 2PhCH@C–, 2-C@CH–
3
C–, ArH), 8.14 (d, 2H, JHH = 8.50 Hz, 2-CH@N–). UV–Vis (DMSO,
According to methods reported in the literature, electrochemi-
cal, chemical (with sodium amalgam and methanol, lithium
aluminum hydride, ferrous oxide or iron) and catalytic (by hydroge-
nation with platinum oxide or Raney nickel) reduction of 2,20-dini-
trobiphenyl indicates that almost every possible intermediate, such
as unreacted dinitrobiphenyl, tar, benzo[c]cinnoline-5-oxide,
benzo[c]cinnoline-5,6-dioxide or various mixtures, may be
obtained. For the synthesis of 2,20-diaminobiphenyl by catalytic
nm): 374(3.92), 341(4.38), 297(4.79). Anal. Calc. for C30H24Cl2N2Zn:
C, 65.65; H, 4.41; N, 5.10. Found: C, 65.72; H, 4.43; N, 5.14%.
2.2.14. Zn(L2)Br2 (5b)
This complex was synthesized by a procedure similar to that for
4b using ZnBr2 (50 mg, 0.222 mmol). Yield: 94%. IR (KBr, cmꢀ1):
1578
m(C@N). 1H NMR (250 MHz, DMSO-d6) d: 6.87–7.47 (m,

72
S. Dehghanpour et al. / Polyhedron 35 (2012) 69–76
Table 1
Crystal data and structure refinement of Co(L1)2Cl2 (1a), Zn(L1)2Br2 (5a) and Hg(L2)Cl2 (7b).
Complex
1a
5a
7b
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C
24H16Cl2CoN4
C24H16Br2N4Zn
585.60
100(2)
C30H24N2Cl2Hg
684.00
200(2)
490.24
120(2)
0.71073
triclinic
0.71073
triclinic
0.71073
triclinic
ꢀ
ꢀ
ꢀ
P1
P1
P1
8.0030(15)
8.8583(16)
15.008(3)
7.9911(15)
8.9325(17)
15.204(3)
9.0800(18)
10.2324(19)
16.779(3)
b (Å)
c (Å)
a
b (°)
(°)
87.038(4)
75.641(3)
87.097(4)
76.363(4)
106.347(3)
91.409(3)
c
(°)
76.732(3)
1003.2(3)
77.021(4)
1027.7(3)
109.919(2)
1393.8(5)
V (Å3)
Z
2
2
2
Dcalc (g cmꢀ3
)
1.623
1.142
1.892
5.103
1.630
5.733
l
(mmꢀ1
)
F(000)
Crystal size
Theta range for data collection
Index ranges
498
576
664
0.6 ꢂ 0.4 ꢂ 0.3
1.40–26.00°
ꢀ9 6 h 6 9
ꢀ10 6 k 6 10
ꢀ18 6 l 6 18
0.708 and 0.580
Full-matrix least-squares on F2
3891/0/280
0.966
0.16 ꢂ 0.11 ꢂ 0.07
1.38–29.99°
ꢀ10 6 h 6 11
ꢀ12 6 k 6 12
0 6 l 6 21
0.716 and 0.437
Full-matrix least-squares on F2
6009/0/281
0.877
0.24ꢂ0.20ꢂ0.12
2.82–28.00°
ꢀ11 6 h 6 11
ꢀ13 6 k 6 13
ꢀ22 6 l 6 21
0.5462 and 0.3399
Full-matrix least-squares on F2
6691/0/316
1.198
Maximum and minimum transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0611
wR2 = 0.1401
R1 = 0.0776
wR2 = 0.1480
0.974 and ꢀ0.638
R1 = 0.0408
wR2 = 0.0707
R1 = 0.0899
wR2 = 0.0786
1.150 and ꢀ1.018
R1 = 0.0373
wR2 = 0.0907
R1 = 0.0403
wR2 = 0.0917
2.670 and ꢀ2.059
Largest difference in peak and hole (e Åꢀ3
)
methods in the presence of hydrazine hydrate, the nature of the cat-
alyst is important. When a Raney nickel catalyst low in aluminum is
used, 2,20-diaminobiphenyl is obtained (in 74–85% yield) if starting
quantities of the dinitro compound of less than 1 g are used. If larger
batches of starting material are used, benzo[c]cinnoline is also ob-
tained. Benzo[c]cinnoline-6-oxide is the product when the dinitro
compound is reduced with hydrogen gas using Pd as a catalyst.
Benzo[c]cinnoline in 80% yield is also the end product when 2,20-
dinitrobiphenyl is reduced in 5% alcoholic potassium hydroxide
using Ru as a catalyst. Reduction of 2,20-dinitrobiphenyl by hydra-
zine hydrate in ethanol using palladized charcoal as a catalyst gave
erratic results [15–20].
The IR spectrum of L1 shows the characteristic vibration band of
the N@N group at 1463 cmꢀ1 [21,22]. The IR spectrum of the free
diimine ligand L2 shows the characteristic band of the diimine
group at 1624 cmꢀ1 [23,24]. The complexes of the type M(L1)2X2
(M = Co(II), Zn(II); X = Cl, Br or I) (1a–6a) show similar IR spectral
features, while the band which is assigned to the N@N stretching
vibration is shifted to lower frequencies relative to the free ligand
upon coordination of the ligand to the metal center. The complexes
of type ML2X2 (M = Co(II), Zn(II); X = Cl, Br or I (1b–6b)) and
Hg(L2)Cl2, (7b) also show similar IR spectral features, exhibiting a
strong band between 1572 and 1583 cmꢀ1, assigned to stretching
vibration of the C@N bond, which is shifted to lower frequencies
in the IR spectra of the complexes relative to the free ligand, due
to coordination of the imine nitrogen to the metal center and
Here, we present the reduction of 2,20-dinitrobiphenyl with
hydrazine hydrate catalyzed by 10% Pd/C. The concentration of
hydrazine appears to be the main factor controlling the nature
and yields of the reduction products [21]. Treating an ethanolic
solution of 2,20-dinitrobiphenyl with hydrazine hydrate using a
molar ratio of 1:4 yields benzo[c]cinnoline (L1) because of the
partial reduction of 2,20-dinitrobiphenyl, while 2,20-diaminobi-
phenyl is formed using a molar ratio of 1:10. The diimine ligand
(L2) was prepared by the reaction of an ethanolic solution of 2,20-
diaminobiphenyl with trans-cinnamaldehyde (molar ratio of 1:2)
(Scheme 1).
p
-back bonding from d(M) to
The absorption spectra of aromatic nitrogen containing com-
pounds absorb in three main regions in UV–Vis spectra. Absorption
bands which are attributed to n ?
ꢁ transitions shift to longer
p
ꢁ(ligand) [23–25].
p
wavelengths by increasing the number of nitrogen atoms in the
molecule. This effect is more intense when the nitrogen atoms
are adjacent [26–28]. The electronic absorption spectrum of
benzo[c]cinnoline agreed with that reported in the literature
[26–28]. The absorption begins at about 384 nm, which is indica-
tive of having two adjacent nitrogen atoms. The absorption spectra
of the complexes Zn(L1)2X2 (X = Cl, Br or I (4a–6a)) show a similar
pattern to the ligand, with different intensities of the bands; this
high molar absorbtivity results from overlapping of the MLCT tran-
sitions with intraligand electronic transitions. A similar absorption
pattern is observed in the cobalt complexes. Furthermore, the
cobalt complexes show additional absorption bands in the visible
region, which is characteristic for d–d transitions in cobalt com-
plexes in a tetrahedral or pseudo-tetrahedral geometry [29,30].
In Co(L1)2X2, the 4A2 ? 4T1(P) transition is observed in the
Complexes of the type ML12X2 (M = Co(II), Zn(II); X = Cl, Br or I)
(1a–6a) were prepared by reacting anhydrous metal halide salts
and benzo[c]cinnoline (L1) using a molar ratio of 1:2 in acetonitrile
under stirring at room temperature. Complexes of the type ML2X2
(M = Co(II), Zn(II); X = Cl, Br or I (1b–6b)) and Hg(L2)Cl2, (7b) were
prepared by reacting equimolar quantities of anhydrous metal
halides salts and the diimine ligand L2 in organic solvents (metha-
nol for the mercury complex and acetonitrile for the other
complexes). All of these complexes were stable solids in air under
ambient conditions.

S. Dehghanpour et al. / Polyhedron 35 (2012) 69–76
73
615–685 nm range and the splitting of the absorption band into
three closely spaced transitions arises from the distortion of the
tetrahedral geometry around the metal center as well as the reduc-
tion of the orbital degeneracy due to the difference in the ligand
field strength of the imine and halide donor atoms [29,30]. This
effect is similar to that reported for [Co(morpholine)2(NCS)2] [29].
The absorption spectra of the ZnL2X2 (X = Cl, Br or I (4b–6b))
and Hg(L2)Cl2, (7b) complexes show intense absorptions in the
UV region (See Section 2). This broad band is attributed to intrali-
gand (
p
?
p
ꢁ) and/or charge transfer transitions. The 4A2 ? 4T1(P)
transition in the cobalt complexes (1b–3b), also split into three clo-
sely spaced transitions, appears as a low intensity band at about
660 nm, similar to that reported for [Co(Phca2en)Br2] [23,24]. A
strong band at about 330 nm is assigned to a ligand-centered
p
?
p
ꢁ transition or/and charge transfer transitions.
The 1H NMR spectra and peak assignments are presented in
Fig. 2. Crystal structure of Zn(L1)2Br2, 5a with the atom-labeling scheme.
Section 2. The peaks are assigned based on the splitting of the
resonance signals, spin coupling constants and the literature. The
1H NMR spectra of the complexes Zn(L1)2X2 (X = Cl, Br or I (4a–
6a)) show three sets of signals in the ratio 1:1:2. The proton signal
shifts observed in the spectra of the complexes relative to the free
ligand, in particular for the hydrogens adjacent to the metal center,
indicate that they are affected by coordination to the metal center.
The 1H NMR spectrum of L2 shows a doublet at 8.09 ppm due to
the CH@N protons. However, the ethylenic H atoms overlap with
the aromatic H atoms of the ligands and appear in the 6.89–
7.45 ppm region. The 1H NMR spectra of the zinc and mercury
complexes ZnL2X2 (X = Cl, Br or I (1b–6b)) and HgL2Cl2 (7b) show
a similar spectroscopic pattern to the ligand L2. However, compar-
ing the proton spectra of the complexes relative to the free diimine
ligand reveal that the more significant shifts involve the iminic
protons. In fact, a downfield shift appears upon coordination.
Furthermore, the coupling constants reported for the adjacent
hydrogens in these complexes (J ꢃ 9, 15 Hz) affirm that they are
placed in trans-positions relative to each other.
Whilst a tetrahedral geometry might be expected for four coor-
dinated Co(II) and Zn(II) centers, the geometries about the M(II)
center in Co(L1)2Cl2 and Zn(L1)2Br2 are distorted. For Co(L1)2Cl2,
the N1–Co1–N1 angle is 108.73(14)°, but the Cl1–Co1–N1 angle,
118.54(11)°, is larger than the tetrahedral value. The average
Co–Cl bond length of 2.25 Å agrees well with the Co–Cl bond
lengths in other tetrahedral cobalt complexes, for example, Co(p-
toluidine)2Cl2, 2.26 Å and Co(bdmpab)Cl2, 2.23 Å [19]. The Co–Nav
bond length of 2.05 Å is normal [31–33].
The angle values around the zinc center (N1–Zn1–N3,
108.10(13)° and Br1–Zn1–Br2, 116.51(3)°) show a distorted tetra-
hedral geometry. The average value of the angles agrees with coor-
dination compounds with similar geometries around the metal
center [34–37]. The average Zn–N and Zn–Br bond distances of
2.09 and 2.37 Å, respectively, agree well with those reported for
other tetrahedral zinc complexes [38,39,40].
The dihedral angles between the planes of the aromatic rings of
each benzo[c]cinnoline unit show the coplanarity of these planes,
(the maximum dihedral angle is 3.35°) leading to considerable pla-
narity of these moieties. However, the two benzo[c]cinnoline units
coordinated to the metal centers are not placed in a plane, and the
dihedral angles between them in the zinc and cobalt complexes are
62.48(5) and63.55(4)°, respectively.
3.2. Crystal structures of Co(L1)2Cl2 (1a) and Zn(L1)2Br2 (5a)
On slow evaporation, single crystals of Co(L1)2Cl2 and
Zn(L1)2Br2, suitable for X-ray diffraction analysis, were grown from
their acetonitrile solutions in air. The crystal structures of the
cobalt and zinc complexes along with the labeling scheme are
shown in Figs. 1 and 2, respectively, and metric parameters are
listed in Tables 1 and 2. These two complexes are isomorphic
Co(L1)2Cl2, 1a, exhibits a supramolecular structure as a result of
p–p stacking of the benzo[c]cinnoline ligands. Each benzo[c]cinn-
oline ligand has two benzo[c]cinnoline neighbors within the
stacks. The mean inter-ring distances between corresponding
atoms of the benzo[c]cinnoline ligand and the two neighboring li-
gands are not equal and fall in the range 3.33–3.45 Å. A related
stacking of the benzo[c]cinnoline ligands was observed for
Zn(L1)2Br2, 5a, with separations of 3.34–3.45 Å (Fig. 3).
ꢀ
and isostructural and crystallize in the triclinic, space group P1
with cell constants deviating by less than 0.2 Å and less than 0.8°.
The N@Nav bond distance is 1.306(5) and 1.297(5) Å in the Co
and Zn complexes, respectively. A weak interaction between the
Co(II) and the nitrogen atom, which is not coordinated to the metal
center, is also observed (Co1–N1, 2.054(4), Co1–N2, 2.835(4) Å).
However some reports on complexes in which benzo[c]cinnoline
acts as
g
2-cis N–N chelating function, giving cis-azo compounds,
do exist [41–43]. A weak interaction of this kind is also observed
in the zinc complex (Zn1–N1, 2.087(4), Zn1–N2, 2.832(4) Å).
3.3. Crystal structure of Hg(L2)Cl2 (7b)
Single crystals of Hg(L2)Cl2 suitable for X-ray diffraction struc-
tural analysis were grown by slow evaporation of a methanolic
solution of the complex in air. The crystal structure of the Hg(L2)Cl2
complex, along with the labeling scheme, is shown in Fig. 4. The
relevant details of the crystals, data collection and structure
Fig. 1. Crystal structure of Co(L1)2Cl2, 1a with the atom-labeling scheme.

74
S. Dehghanpour et al. / Polyhedron 35 (2012) 69–76
Table 2
Selected bond distances (Å) and angles (°) for Co(L1)2Cl2 (1a), Zn(L1)2Br2 (5a) and Hg(L2)Cl2 (7b).
1a
5a
7b
Co(1)–N(10)
Co(1)–N(1)
Co(1)–Cl(2)
Co(1)–Cl(1)
2.054(4)
2.057(4)
2.2479(13)
2.2494(13)
Zn(1)–N(1)
Zn(1)–N(3)
Zn(1)–Br(1)
Zn(1)–Br(2)
2.087(4)
2.092(4)
2.3666(9)
2.3712(9)
Hg(1)–Cl(1)
Hg(1)–N(1)
Hg(1)–Cl(2)
Hg(1)–N(2)
2.3685(17)
2.371(4)
2.3774(17)
2.400(4)
N(1)–N(2)
1.306(5)
108.73(14)
117.01(11)
98.88(10)
100.14(10)
118.54(11)
114.38(5)
N(1)–N(2)
1.297(5)
108.10(13)
118.00(10)
99.47(10)
98.90(10)
116.52(10)
116.51(3)
N(1)–C(13)
1.280(7)
112.38(12)
95.80(11)
96.98(11)
140.57(7)
86.21(14)
114.7(3)
N(10)–Co(1)–N(1)
N(10)–Co(1)–Cl(2)
N(1)–Co(1)–Cl(2)
N(10)–Co(1)–Cl(1)
N(1)–Co(1)–Cl(1)
Cl(2)–Co(1)–Cl(1)
N(1)–Zn(1)–N(3)
N(1)–Zn(1)–Br(1)
N(3)–Zn(1)–Br(1)
N(1)–Zn(1)–Br(2)
N(3)–Zn(1)–Br(2)
Br(1)–Zn(1)–Br(2)
Cl(1)–Hg(1)–N(1)
Cl(1)–Hg(1)–N(2)
N(1)–Hg(1)–Cl(2)
Cl(1)–Hg(1)–Cl(2)
N(1)–Hg(1)–N(2)
C(1)–N(1)–Hg(1)
Fig. 3. A packing view of Zn(L1)2Br2, 5a along the a axis.
refinement are found in Table 1 and the selected bond distances and
angles are presented in Table 2. The compound crystallizes in the
triclinic system and the space group was determined as P1.
Despite the fact that mercury(II) halide complexes also form
dimeric or polymeric structures [49–52], here we deal with a
monomeric structure of the mercury complex, as shown in Fig. 4,
probably due to the large steric crowding provided by the diimine
ligand. The average Hg–N and Hg–Cl bond distances (2.38 and
2.37 Å, respectively) are similar to those found for monomeric
tetrahedral mercury(II) complexes [53–56].
Different conformational isomers can be considered for the dii-
mine ligand (L2), since the two biphenyl rings can adopt different
orientations relative to each other as well as different geometrical
isomers with respect to the C@N or C@C bonds. Fig. 6 illustrates
the possible geometrical isomers with respect to the C@N bond
(cis–cis, trans–cis and trans–trans). As shown in Fig. 4, the ligand
is likely to prefer a trans–trans arrangement in this complex. Con-
sidering the average value of the torsion angle of the N@C–C@C
moiety and the dihedral angle between the phenyl ring and the
chain connecting the ring to the coordinated N-atom (3.51°), this
reveals that they are coplanar. This degree of coplanarity, which
ꢀ
While a tetrahedral geometry might be expected for a four coor-
dinated Hg(II) center, the coordination sphere around the metal ion
is highly distorted, probably due to the presence of the seven-
membered chelate ring. The chelate bite angle in the seven-
membered ring, N1–Hg–N2 (86.21(14)°) and the Cl1–Hg–Cl2 angle
(140.57(7)°) are both significantly distorted from 109.5°. The aver-
age values of the other angles (N–Hg–Cl) are 104.96°.
The two biphenyl rings in the diimine ligand are not placed in a
plane and the dihedral angle between them is 68.73°. Generally,
the non-planar nature of biphenyl rings and the ability of the
ligand to twist out of planarity is a characteristic property of biphe-
nyl-based ligands. The biphenyl-bridged ligand backbone has pre-
viously been used to enforce cis-a geometries in transition metal
complexes [44,45].
Coordination of the diimine ligand to the metal center results in
a seven-membered chelate ring, which adopts a pronounced boat
conformation (Fig. 5). The N1 atom and one of the phenyl rings
are on the same side of the mean plane of Hg1, N2, C1 and C6,
which forms dihedral angles of 61.99° and 48.02° with the C5–
C6–C7–C8 and N1–Hg1–N2 planes, respectively. The endocyclic
torsion angles Hg1–N1–C1–C6, N1–C1–C6–C7 and C1–C6–C7–
C12 are 76.95, 3.29 and 73.25, respectively [46–48].
allows for increased
p-conjugation in the ligand, is consistent
with the observed C–C bond distances in the coordinated ligand
(C(13)–C(14), 1.433(8) Å and C(15)–C(16), 1.431(8) Å), which
are shorter than a typical single bond distance. The aryl–aryl
bond distance in the biphenyl unit is in the range of a single bond
(1.494(7) Å) as a result of non-planar nature of the biphenyl rings
[57].

S. Dehghanpour et al. / Polyhedron 35 (2012) 69–76
75
Fig. 4. Representation of molecular structure of Hg(L2)Cl2 7b with the atom-labeling scheme.
benzo[c]cinnoline, while 2,20-diaminobiphenyl was obtained using
0
a molar ratio of 1:10. The N2,N2 -bis(3-phenylallylidene)biphenyl-
2,20-diamine was prepared by the reaction of an ethanolic solution
of 2,20-diaminobiphenyl with trans-cinnamaldehyde.
A series of ML12X2 and ML2X2 complexes (M = Co(II), Zn(II);
X = Cl, Br or I and Hg(L2)Cl2) have been synthesized. The crystal
structures of Co(L1)2Cl2, Zn(L1)2Br2 and Hg(L2)Cl2 were determined
using single crystal X-ray diffraction. In these three complexes, the
coordination polyhedron about the central metal ion is best
described as a distorted tetrahedron. The Co(L1)2Cl2, and Zn(L1)2Br2
complexes exhibit supramolecular structures resulting from
p–p
stacking of the benzo[c]cinnoline ligands.
Fig. 5. Boat conformation of the seven-membered chelate ring.
Acknowledgment
Financial support by the Alzahra University is gratefully
acknowledged.
Appendix A. Supplementary data
CCDC 854700, 854701 and 854702 contain the supplementary
crystallographic data for 7a, 5a and 1a, respectively. 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, Cambridge CB2 1EZ, UK; fax: (+44)
1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
N
N
N
N
N
N
References
trans-trans cis-trans
cis-cis
[1] F. Fache, E. Schulz, M.L. Tammasino, M. Lemaire, Chem. Rev. 100 (2000) 2159.
[2] G. Chelucci, R.P. Thummel, Chem. Rev. 102 (2002) 3129.
[3] H.A. McManus, P.J. Guiry, Chem. Rev. 104 (2004) 4151.
Fig. 6. Possible geometrical isomers with respect to the C@N bond.
[4] K.C. Gupta, A.K. Sutar, Coord. Chem. Rev. 252 (2008) 1420.
[5] B.L. Small, M. Brookhart, A.M.A. Bennett, J. Am. Chem. Soc. 120 (1998) 4049.
[6] J.J. Cid, J.J. Yum, S. Jang, M.K. Nazeeruddin, E. Martinez-Ferrero, E. Palomares, J.
Ko, M. Gratzel, T. Torres, Angew. Chem., Int. Ed. Engl. 46 (2007) 8358.
[7] A. Togni, L.M. Venanzi, Angew. Chem., Int. Ed. Engl. 33 (1994) 497.
[8] D.D. Perrin, W.L. Armarego, D.R. Perrin, Purification of Laboratory Chemicals,
Pergamon, New York, 1996.
4. Conclusions
Reduction of 2,20-dinitrobiphenyl with hydrazine hydrate
catalyzed by 10% Pd/C has been investigated. Reduction using a
molar ratio of 1:4 (2,20-dinitrobiphenyl:hydrazine hydrate) yields
[9] BrukerSAINTPlus, Data Reduction and Correction Program version 6.01, Bruker
AXS, Madison, Wisconsin, USA, 1998.

76
S. Dehghanpour et al. / Polyhedron 35 (2012) 69–76
[10] G.M. Sheldrick, SADABS version 2.01, Bruker/Siemens Area Detector
Absorption Correction Program, Bruker AXS, Madison, Wisconsin, USA, 1998.
[11] G.M. Sheldrick, SHELXTL version 5.10, Structure Determination Software Suite,
Bruker AXS, Madison, Wisconsin, USA, 1998.
[12] Bruker APEX2 softwarwe package, Bruker AXS Inc., 5465, East Cheryl Parkway,
Madison, WI 5317, 2005.
[13] SAINT PLUS, version 6.02, Bruker AXS, Inc., Madison, WI, 1999.
[14] G.M. Sheldrick, SADABS ‘Siemens Area Detector Absorption Correction’,
University of Gottingen, Gottingen, Germany, 1996.
[35] S.G. Roh, Y.C. Park, D.K. Park, T.J. Kim, J.H. Jeong, Polyhedron 20 (2001) 1961.
[36] H.R. Khavasi, A. Abedi, V. Amani, B. Notash, N. Safari, Polyhedron 27 (2008)
1848–1854.
[37] Y. Qu, S.M. Zhang, X.Z. Wu, H. Zhang, Z.D. Lin, Acta Crystallogr., Sect. E 64
(2008) m732.
[38] G. Bhosekar, I. Jeb, N. Lehnert, C. Nather, Eur. J. Inorg. Chem. (2008) 605–611.
[39] M. Wriedt, I. Jeb, C. Nather, Eur. J. Inorg. Chem. (2009) 363–372.
[40] J.J. Wang, L.F. Yan, Z.X. Li, Z. Chang, T.L. Hu, X.H. Bu, Inorg. Chim. Acta 362
(2009) 3147.
[15] H. Bjorsvik, R.R. Gonzalez, L. Liguori, J. Org. Chem. 69 (2004) 7720.
[16] A.E. Blood, C.R. Noller, J. Org. Chem. 22 (1957) 711.
[17] J. Adell, L. Spialter, J. Hollander, J. Org. Chem. 21 (1956) 1051.
[18] R.E. Moore, A. Furst, J. Org. Chem. 23 (1958) 1504.
[41] R.P. Bennett, Inorg. Chem. 9 (1970) 2184.
[42] Y. Yu, A.R. Sadique, J.M. Smith, T.R. Dugan, R.E. Cowley, W.W. Brennessel, C.J.
Flaschenriem, E. Bill, T.R. Cundari, P.L. Holland, J. Am. Chem. Soc. 130 (2008)
6624.
[19] A. Furst, R.C. Berlo, S. Hooton, Chem. Rev. 64 (1964) 51.
[20] V. Benin, P. Kaszynski, M. Pink, V.G. Young Jr., J. Org. Chem. 65 (2000) 6388.
[21] J.W. Barton, Adv. Heterocycl. Chem. 24 (1979) 151.
[22] P. Patnaik, Dean’s Analytical Chemistry Handbook, McGraw-Hill, 2004.
[23] J.W. Robinson, Practical Handbook of Spectroscopy, CRC, 1991.
[24] J.R. Dyer, Applications of Absorption Spectroscopy of Organic Compounds,
Prentice-Hall, New Jersey, 1965.
[25] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Complexes, fourth ed., John Wiley & Sons, USA, 1992.
[26] G.M. Badger, R.S. Pearce, R. Pettit, J. Chem. Soc. (1951) 3199–3203.
[27] J.F. Corbett, Spectr. Chim. Acta 20 (1964) 1665.
[43] J.E. Hill, P.E. Fanwick, I.P. Rothwell, Inorg. Chem. 30 (1991) 1143.
[44] M. Amirnasr, G. Kickelbick, S. Dehghanpour, Helv. Chim. Acta 89 (2006) 274.
[45] P.D. Knight, P. Scott, Coord. Chem. Rev. 242 (2003) 125.
[46] V. Broughton, G. Bernardinelli, A.F. Williams, Inorg. Chim. Acta 275 (1998) 279.
[47] A. Knodler, M. Wanner, J. Fiedler, W. Kaim, J. Chem. Soc., Dalton Trans. (2002)
3079–3084.
[48] N. Liu, A.L. Cheng, H.Q. Peng, E.Q. Gao, M.Y. He, Struct. Chem. 18 (2007) 43.
[49] T.S.B. Baul, A. Lycka, R. Butcher, F.E. Smith, Polyhedron 23 (2004) 2323.
[50] B. Chand, U. Ray, P.K. Santra, G. Lu, T.H. Mostafa, C. Sinha, Polyhedron 22
(2003) 1205.
[51] L.Y. Wang, C.X. Zhang, D.Z. Liao, Z.H. Jiang, S.P. Yan, J. Coord. Chem. 58 (2005)
969.
[28] D.L. Vivian, Nature 188 (1960) 746.
[29] A.B.P. Lever, Inorganic Electronic Spectroscopy, second ed., Elsevier, The
Netherland, 1984. p. 496.
[30] M. Amirnasr, A.H. Mahmoudkhani, A. Gorji, S. Dehghanpour, H.R. Bijanzadeh,
Polyhedron 21 (2002) 2733.
[31] W.R. Scheidt, J.C. Hanson, P.G. Rasmussen, Inorg. Chem. 8 (1969) 2398.
[32] P. Yang, Y. Yang, C. Zhang, X. Yang, H. Hub, Y. Gao, B. Wua, Inorg. Chim. Acta
362 (2009) 89.
[52] G. Meyer, P. Nockemann, Z. Anorg. Allg. Chem. 629 (2003) 1447.
[53] L.C. Ferreira, C.A.L. Filgueiras, L.C. Visentin, J. Bordinhao, M. Hornerb, Z. Anorg.
Allg. Chem. 634 (2008) 1896.
[54] M. Yousefi, N. Tadayon Pour, V. Amani, H.R. Khavasi, Acta Crystallogr., Sect. E
64 (2008) m1259.
[55] R. Ahmadi, A. Ebadi, K. Kalateh, A. Norouzi, V. Amani, Acta Crystallogr., Sect. E
64 (2008) m1407.
[33] A. Hoffmann, J. Boorner, U. Floorke, S. Herres-Pawlis, Inorg. Chim. Acta 362
(2009) 1185.
[56] M. Yousefi, M.R. Allahgholi Ghasri, A. Heidari, V. Amani, Acta Crystallogr., Sect.
E 65 (2009) m9.
[34] F.J. Barros-Garcia, A. Bernalte-Garcia, A.M. Lozano, F. Luna-Giles, E. Vinuelas-
Zahinos, Polyhedron 24 (2005) 129.
[57] G.J.P. Britovsek, J. England, A.J.P. White, Dalton Trans. (2006) 1399–1408.