Metal derivatives of N-substituted imidazolidine-2-thiones with d10 metal ions (Zn-Hg): Synthesis, spectroscopy, ESI-mass and structures

Article abstract of DOI:10.1016/j.poly.2014.10.016

N-substituted 1,3-imidazolidine-2-thiones (L^I-NMe; L^II-NEt; L^III-NPrⁿ) on reacting with Zn(II), Cd(II) and Hg(II) halides in methanol have yielded the mononuclear complexes [ZnCl₂(L^II-NEt-S)₂] 1, [ZnI₂(L^I-NMe-S)₂] 2, [CdBr₂(L^I-NMe-S)₂] 3, [CdBr₂(L^II-NEt-S)₂] 4, [CdI₂(L^I-NMe-S)₂] 5, [HgCl₂(L^I-NMe-S)₂] 6, [HgCl₂(L^III-NPrⁿ-S)₂] 7 and [HgI₂(L^I-NMe-S)₂] 8. All these complexes have been characterized by elemental analysis, spectroscopy (IR, ¹H NMR), ESI-mass and X-ray crystallography. Complexes 1-6 and 8 crystallized in the monoclinic system, with each having the space group P2₁/c except for complex 4 which has the space group C2/c, and complex 7 crystallized in the trigonal system with the space group R-3c. Interestingly, the complex molecules adopt four types of conformations which give rise to different patterns of intermolecular interactions and hence 2D (1-6, 8) or 1D (7) polymeric networks are obtained. ESI mass data support the formation of [M-X]⁺ ions (X = halogen) in complexes 1-7.

Full text of DOI:10.1016/j.poly.2014.10.016

Polyhedron 87 (2015) 17–27
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Metal derivatives of N-substituted imidazolidine-2-thiones with d10
metal ions (Zn–Hg): Synthesis, spectroscopy, ESI-mass and structures
a
a
a
a
Tarlok S. Lobana a, , Amanpreet K. Sandhu , Amanpreet K. Jassal , Geeta Hundal , R.K. Mahajan ,
⇑
Jerry P. Jasinski b, Ray J. Butcher c
a Department of Chemistry, Guru Nanak Dev University, Amritsar 143 005, India
b Department of Chemistry, Keene State College, Keene, NH 03435-2001, USA
c Department of Chemistry, Howard University, Washington, DC 20059, USA
a r t i c l e i n f o
a b s t r a c t
N-substituted 1,3-imidazolidine-2-thiones (LI-NMe; LII-NEt; LIII-NPrn) on reacting with Zn(II), Cd(II) and
Hg(II) halides in methanol have yielded the mononuclear complexes [ZnCl2(LII-NEt-S)2] 1, [ZnI2
(LI-NMe-S)2] 2, [CdBr2(LI-NMe-S)2] 3, [CdBr2(LII-NEt-S)2] 4, [CdI2(LI-NMe-S)2] 5, [HgCl2(LI-NMe-S)2] 6,
[HgCl2(LIII-NPrn-S)2] 7 and [HgI2(LI-NMe-S)2] 8. All these complexes have been characterized by elemental
analysis, spectroscopy (IR, 1H NMR), ESI-mass and X-ray crystallography. Complexes 1–6 and 8 crystal-
lized in the monoclinic system, with each having the space group P21/c except for complex 4 which
has the space group C2/c, and complex 7 crystallized in the trigonal system with the space group R-3c.
Interestingly, the complex molecules adopt four types of conformations which give rise to different
patterns of intermolecular interactions and hence 2D (1–6, 8) or 1D (7) polymeric networks are obtained.
ESI mass data support the formation of [MÀX]+ ions (X = halogen) in complexes 1–7.
Article history:
Received 7 July 2014
Accepted 7 October 2014
Available online 25 October 2014
Keywords:
N-methyl-imidazolidine-2-thione
N-ethyl-imidazolidine-2-thione
N-n-propyl-imidazolidine-2-thione
Zinc
Cadmium
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
relatively less as compared to 1,3-imidazolidine-2-thione com-
plexes [34,35,38,18,39,41–43]. It may be noted that there are a
The coordination chemistry of heterocyclic thiones has invited
the attention of many research workers over the past four decades,
as revealed by several reviews in this area [1–5]. These thio ligands
have the propensity to coordinate to a metal as a neutral ligand or as
an anionic ligand. Due to the presence of the soft sulfur donor atom
in the vicinity of the nitrogen atom in the heterocyclic ring, these
thio ligands exhibit several types of coordination modes [1–16].
Among these heterocyclic thiones, 1,3-imidazolidine-2-thione and
its N-substituted derivatives (Chart 1) have formed mononuclear,
dinuclear and polynuclear complexes with coinage metals (Cu–Au)
[17–33], and post transition metals (Zn–Hg) [34–38,18,39–43]. In
addition, these ligands with copper salts have displayed interesting
chemical reactivity, such as C–S rupture with the in situ formation
of sulfate and a new type of reaction products [15,16].
few reports on the biological properties of 1,3-imidazolidine-2-thi-
one (LIV-NH) complexes with ZnII and CdII, but none with HgII
[36,37]. It is noted that a complex of 1,3-imidazolidine-2-thione
with ZnII has shown higher biological activity against Pseudomonas
aeruginosa and Escherichia coli than its CdII analog [36]. In this
paper, the coordination compounds of ZnII, CdII and HgII with
N-substituted 1,3-imidazolidine-2-thiones (LI-NMe; LII-NEt;
LIII-NPrn) (Chart 1) are reported so as to provide a status report
on the coordination chemistry of Zn–Hg metals with the thio
ligands under study.
2. Experimental
2.1. Materials and techniques
Recently, coordination compounds of post transition metals (Zn,
Cd, Hg) with 1,3-imidazolidine-2-thione (LIV-NH, R = H, Chart 1)
have been reported from this laboratory [43]. In the literature,
the number of compounds of post transition metals (Zn, Cd, Hg)
reported with substituted imidazolidine-2-thiones [36,37,40] are
The thio ligand 1-methyl-imidazolidine-2-thione (LI-NMe) was
prepared by the addition of carbon disulfide dropwise to a cooled
solution of 1-methyl-ethylenediamine in ethanol and water. The
reaction mixture was heated under reflux (110 °C) for 1 h and conc.
HCl was added. The mixture was heated under reflux for a further
period of 10 h. The reaction mixture was cooled and stored in a
freezer. The resulting precipitate were filtered and washed with
⇑
Corresponding author. Tel.: +91 183 2258802x3195; fax: +91 183 2258820.
E-mail address: tarlokslobana@yahoo.co.in (T.S. Lobana).
http://dx.doi.org/10.1016/j.poly.2014.10.016
0277-5387/Ó 2014 Elsevier Ltd. All rights reserved.

18
T.S. Lobana et al. / Polyhedron 87 (2015) 17–27
cold acetone to give the desired ligand. In a similar manner, 1-
ethyl-imidazolidine-2-thione (LII-NEt) and n-propyl-imidazoli-
dine-2-thione (LIII-NPrn) were prepared [44]. The metal salts
{ZnX2 (X = Cl, I), CdX2 (X = Br, I) and HgX2 (X = Cl, I)} were procured
from Spectrochem Pvt. Ltd. The melting points were determined
with a Gallenkamp electrically heated apparatus. The IR spectra
were recorded using KBr pellets on Varian 660 FT IR and Perkin
Elmer FT IR spectrometers in the 4000–200 cmÀ1 range. The 1H
NMR spectra were recorded in CDCl3 using a Bruker Avance II
400 NMR spectrometer at 400 MHz and a JEOL AL300 FT 1H NMR
spectrometer at 300 MHz using TMS as an internal reference. The
ESI-MS mass spectrometer used was a microTOF-QII 10356 in the
positive mode.
added dichloromethane (5 mL) and methanol (5 mL). The slow
evaporation at room temperature formed colorless crystals of 3
(76%, m.p. 148–150 °C). Anal. Calc. for C8H16Br2CdN4S2: C, 19.03;
H, 3.02; N, 11.10. Found: C, 8.87; H, 3.06; N, 11.21%. IR bands
(KBr, cmÀ1):
m(N–H) 3294 s;
m(C–H) 2921 w, 2892 w; m(C–C) +
m(C–N) + d(C–H) 1543 s, 1510 s, 1470 m, 1403 w; 1329 m, 1219
s, 1198 m; m(C–S) 1113 s; 1026 w, 959 w, 635 m, 541 m, 504 m.
1H NMR data (CDCl3 + [D6]DMSO, d ppm): 7.75 (s, 2H, NH), 3.67
(m, 8H, C4,5H), 3.07 (m, 6H, CH3). ESI mass data, calc. for
[MÀ79]+, {C8H16BrCdN4S2} m/z: 424.9; observed m/z: 423.2.
2.2.4. Synthesis of [CdBr2(LII-NEt-S)2] (4)
To
a solution of 1-ethyl-imidazolidine-2-thione (0.0235 g,
0.181 mmol) in methanol (5 mL) was added a solution of cad-
mium(II) bromide (0.025 g, 0.092 mmol) in methanol (5 mL). The
reaction mixture was stirred for 2 h at room temperature and slow
evaporation at room temperature formed colorless crystals of 4
(71%, m.p. 118–120 °C). Anal. Calc. for C10H20Br2CdN4S2: C, 22.55;
H, 3.78; N, 10.52. Found: C, 22.20; H, 3.75; N, 10.58%. IR bands
2.2. Synthesis of the complexes
2.2.1. Synthesis of [ZnCl2(LII-NEt-S)2] (1)
To
a solution of 1-ethyl-imidazolidine-2-thione (0.047 g,
0.362 mmol) in methanol (5 mL) was added a solution of zinc(II)
chloride (0.025 g, 0.183 mmol) in methanol (5 mL). The reaction
mixture was stirred for 2 h at room temperature. To this mixture
was added dichloromethane (5 mL) and then slow evaporation at
room temperature formed colorless crystals of 1 (70%, m.p.
155–157 °C). Anal. Calc. for C10H20Cl2N4S2Zn: C, 30.28; H, 5.08; N,
14.12. Found: C, 30.22; H, 5.01; N, 14.02%. IR bands (KBr, cmÀ1) :
(KBr, cmÀ1):
(C–C) + (C–N) + d(C–H) 1515 s, 1453 m; 1380 w, 1321 m, 1266
s;
m(N–H) 3250 s; m(C–H) 2971 m, 2927 m, 2881 m;
m
m
m
(C–S) 1123 s; 1077 w, 1031 w, 949 w, 791 w, 619 m, 550 m,
502 m. 1H NMR data (CDCl3 , d ppm): 7.95 (s, 2H, NH), 3.76 (m,
8H, C4,5H), 3.61 (q, 4H, N-CH2), 1.22 (t, 6H, J, 5.43, Hz, CH3). ESI
mass data, calc. for [MÀ79]+, {C10H20BrCdN4S2} m/z: 452.9;
observed m/z: 452.9.
m
(N–H) 3244 s;
C) + (C–N) + d(C–H) 1516 s, 1479 m, 1460 m; 1381 m, 1358 w,
1341 w, 1324 m, 1209 s, 1269 s, 1203 w;
m(C–H) 3025 w, 2977 m, 2934 m, 2888 m; m(C–
m
2.2.5. Synthesis of [CdI2(LI-NMe-S)2](5)
m
(C–S) 1127 s; 1079 m,
976 w, 951 m, 794 m, 649 w, 620 m, 586 s, 506 s. 1H NMR data (CDCl3,
d ppm): 8.42 (s, 2H, NH), 3.72 (m, 8H, C4,5H), 3.57 (m, 4H, N-CH2),
1.20 (t, 6H, J, 7.2 Hz, CH3). ESI-mass data, calc. for [MÀ35]+, formula
{C10H20ClN4S2Zn}, m/z: 359.0; observed m/z: 359.0.
To
a
solution of 1-methyl-imidazolidine-2-thione (0.015 g,
solution of
0.135 mmol) in methanol (5 mL) was added
a
cadmium(II) iodide (0.025 g, 0.068 mmol) in methanol (5 mL).
The reaction mixture was stirred for 2 h at room temperature
and slow evaporation at room temperature formed pale yellow
crystals of 5 (70%, m.p 124–126 °C). Anal. Calc. for C8H16CdI2N4S2:
C, 16.05; H, 2.69; N, 9.36. Found: C, 16.08; H, 2.65; N, 9.25%. IR
2.2.2. Synthesis of [ZnI2(LI-NMe-S)2] (2)
To
a solution of 1-methyl-imidazolidine-2-thione (0.018 g,
bands (KBr, cmÀ1):
w; (C–C) +
1328 s, 1300 s, 1288 s, 1275 s, 1195 s;
m
(N–H) 3314 s;
m(C–H) 2917 m, 2890 m, 2793
0.155 mmol) in methanol (5 mL) was added a solution of zinc(II)
iodide (0.025 g, 0.078 mmol) in methanol (5 mL). The reaction mix-
ture was stirred for a period of 2 h at room temperature and a
white precipitate was formed. To the precipitate was added dichlo-
romethane (5 mL) and methanol (5 mL). Slow evaporation at room
temperature formed colorless crystals of 2 (70%, m.p. 158–160 °C).
Anal. Calc. for C8H16I2N4S2Zn: C, 17.45; H, 2.75; N, 10.18. Found: C,
m
m(C–N) + d(C–H) 1541 s, 1504 s, 1469 s, 1401 m;
m(C–S) 1113 s; 1022 m,
956 m, 634 s, 504 s. 1H NMR data (CDCl3 + [D6]DMSO, d ppm):
7.45 (s, 2H, NH), 3.69 (m, 8H, C4,5H), 3.09 (m, 6H, CH3). ESI mass
data, calc. for [MÀ127]+, {C8H16CdIN4S2} m/z: 472.9; observed
m/z: 472.9.
17.58; H, 2.68; N, 10.15%. IR bands (KBr, cmÀ1):
(C–H) 2919 w, 2890 w; (C–C) + (C–N) + d(C–H) 1541 s, 1508 s,
1469 m, 1401 m; 1325 s, 1300 s, 1288 s, 1194 m; (C–S) 1111s;
m(N–H) 3307 s;
2.2.6. Synthesis of [HgCl2(LI-NMe-S)2] (6)
m
m
m
To a solution of 1-methyl-imidazolidine-2-thione (0.0215 g,
0.185 mmol) in methanol (5 mL) was added a solution of mer-
cury(II) chloride (0.025 g, 0.092 mmol) in methanol (5 mL). The
reaction mixture was stirred for 2 h at room temperature and a
white precipitate was formed. To the precipitate was added dichlo-
romethane (5 mL) and methanol (5 mL). Slow evaporation at room
temperature formed colorless crystals of 6 (70%, m.p 140–142 °C).
Anal. Calc. for C8H16Cl2HgN4S: C, 19.07; H, 3.20; N, 11.12. Found: C,
m
1022 m, 955 w, 633 m, 504 s. 1H NMR data (CDCl3 + [D6]DMSO,
d ppm): 7.04 (s, 2H, NH), 3.73 (m, 8H, C4,5H), 3.14 (m, 6H, CH3).
ESI-mass data, calc. for [MÀ127]+, formula {C8H15IN4S2Zn}, m/z:
421.9; observed m/z: 422.9.
2.2.3. Synthesis of [CdBr2(LI-NMe-S)2] (3)
19.10; H, 2.96; N, 11.20%. IR bands (KBr, cmÀ1):
(C–H) 2928 w, 2888 w; (C–C) + (C–N) + d(C–H) 1556 s, 1515 s,
1472 m, 1421 w, 1407 m; 1334 w, 1310 s, 1288 s, 1195 w;
m
(N–H) 3219 s;
To
a solution of 1-methyl-imidazolidine-2-thione (0.021 g,
0.181 mmol) in methanol (5 mL) was added a solution of cad-
mium(II) bromide (0.025 g, 0.092 mmol) in methanol (5 mL). The
reaction mixture was stirred for a period of 2 h at room tempera-
ture and a white precipitate was formed. To the precipitate was
m
m
m
m
(C–S) 1113 s; 960 m, 634 m, 583 m, 500 s. 1H NMR data
([D6]DMSO, d ppm): 8.87 (s, 2H, NH), 3.86 (m, 4H, C4H), 3.72
(m, 4H, C5H), 3.13 (m, 6H). ESI mass data, calc. for [MÀ35]+, [C8H16
ClHgN4S] m/z: 469.0; observed m/z: 469.0. Other peaks, calc. for
[HgCl(LI-NMe-S)]+, m/z: 353.0, observed m/z: 353.0; calc. for
[Hg(LI-NMe-S)2-H]+ m/z: 433.0; observed m/z: 433.0.
R = Me;
R = Et;
R = Prn;
R =H ,
LI - NMe
LII -NEt
LIII -NPrn
LIV-NH
NR
HN
2.2.7. Synthesis of [HgCl2(LIII-NPrn-S)2] (7)
To
a solution of 1-propyl-imidazolidine-2-thione (0.027 g,
S
0.184 mmol) in methanol (5 mL) was added a solution of mer-
cury(II) chloride (0.025 g, 0.092 mmol) in methanol (5 mL). The
Chart 1. Heterocyclic thione ligands.

T.S. Lobana et al. / Polyhedron 87 (2015) 17–27
19
Table 1
Crystallographic data for complexes 1–8.
1
2
3
4
Empirical formula
M
C
10H20Cl2N4S2Zn
C8H16I2N4S2Zn
550.57
C8H16Br2CdN4S2
504.60
C10H20Br2CdN4S2
532.64
396.99
T (K)
173(2)
296(2)
296(2)
173(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c
12.3192(4)
10.4013(4)
13.0932(4)
90.00
monoclinic
P21/c
7.2991(6)
14.8870(12)
15.2939(12)
90.00
monoclinic
P21/c
7.1442(3)
14.4504(5)
15.3547(5)
90.00
monoclinic
C1 2/c
13.0221(10)
10.5580(8)
13.3815(8)
90.00
a
(°)
b (°)
96.209(3)
90.00
1667.86(10)
4
1.580
7.270
93.496(3)
90.00
1658.8(2)
4
2.205
5.441
93.0550(10)
90.00
1582.91(10)
4
2.117
6.677
100.678(7)
90.00
1807.9(2)
4
1.957
5.852
c
(°)
V (Å3)
Z
Dcalc (g cmÀ3
)
l
(mmÀ1
)
F(000)
816
1036
968
1032
Reflections collected
Unique reflections
Data/restraints/parameters
11209
17341
18684
7719
3160 (Rint, 0.0464)
3160/0/175
2885
4413 (Rint, 0.0258)
4413/2/162
3813
4733 (Rint, 0.0421)
4733/2/162
3460
2235 (Rint, 0.0307)
2235/5/97
1733
Reflections with [I > 2r(I)]
R indices [I > 2r(I)]
R1
WR2
0.0402
0.1084
0.0244
0.0586
0.0413
0.0892
0.0327
0.0697
R indices (all data)
R1
0.0435
0.0304
0.0646
0.0510
WR2
0.1120
0.799 and À0.634
0.0613
0.491 and À1.211
0.0973
1.389 and À0.896
0.0772
0.487 and À0.664
Largest difference in peak and hole (e ÅÀ3
)
5
6
7
8
Empirical formula
M
C8H16CdI2N4S2
598.57
C8H16Cl2HgN4S2
503.86
C12H24Cl2Hg N4S2
559.96
C8H16HgI2N4S2
686.76
T (K)
295(2)
173(2)
173(2)
173(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c
7.4457(8)
15.0494(13)
15.4591(16)
90.00
monoclinic
P21/c
13.0806(3)
7.99662(16)
14.3383(3)
90.0
trigonal
R-3c
20.9760(8)
20.9760(8)
22.6458(10)
90.00
monoclinic
P21/c
7.3280(2)
14.9890(5)
15.2160(6)
90.0
a
(°)
b (°)
93.362(11)
90.00
1729.3(3)
4
2.299
5.062
100.243(2)
90.0
1475.90(5)
4
2.267
11.057
90.00
120.00
8629.1(8)
18
1.940
93.169(3)
90.0
1668.76(10)
4
2.734
13.161
c
(°)
V (Å3)
Z
Dcalc (g cmÀ3
)
l
(mmÀ1
)
8.521
F(000)
1112
952
4860
1240
Reflections collected
Unique reflections
Data/restraints/parameters
16170
13277
9482
18457
6547 (Rint, 0.0419)
6547/0/157
4822
4130 (Rint, 0.0300)
4130/0/165
3560
3238 (Rint, 0.0337)
3238/0/97
2608
5515 (Rint, 0.0586)
5515/2/163
4529
Reflections with [I > 2r(I)]
R indices [I > 2r(I)]
R1
WR2
0.0604
0.1211
0.0244
0.0555
0.0304
0.0596
0.0402
0.0928
R indices (all data)
R1
0.0865
0.0314
0.0459
0.0530
WR2
0.1339
2.634 and À1.966
0.0577
1.766 and À0.940
0.0644
1.540 and À1.548
0.0995
3.025 and À2.776
Largest difference in peak and hole (e ÅÀ3
)
dichloromethane (5 mL) and methanol (5 mL). Slow evaporation
at room temperature formed colorless crystals of 7 (75%, m.p
123–125 °C). Anal. Calc. for C12H24Cl2HgN4S2: C, 25.74; H, 4.32; N,
10.01. Found: C, 25.78; H, 4.40; N, 10.10%. IR bands (KBr, cmÀ1):
S
NH
S
=
NR
HN
S
NH
M
NH
m
m
(N–H) 3234 s;
(C–C) + (C–N) + d(C–H) 1542 s, 1514 s, 1479 s, 1462 m, 1443 w,
(C–S)
m(C–H) 3018 w, 2962 s, 2928 s, 2896 m, 2871 m;
X
X
S
m
R = Me (2, 3, 5, 6, 8); Et (1, 4); Prn(7)
X = Cl(1, 6,7); Br(3, 4); I(2, 5, 8)
M = Zn(1, 2); Cd(3, 4, 5): Hg(6, 7, 8)
1383 w, 1360 w, 1345 m, 1317 s, 1288 s, 1252 s, 1200 m;
m
1-8
1127 s; 1082 w, 1033 w, 981 w, 896 w, 881 m, 797 w, 650 w,
620 s, 559 s, 502 s. 1H NMR data (CDCl3 , d ppm): 9.07 (s, 2H,
NH), 3.78 (m, 8H, C4,5H), 3.48 (m, 4H, N–CH2), 1.65 (m, 4H, CH2),
0.92 (m, 6H, CH3). ESI mass data: calc. for [MÀ35]+, {C12H24ClHgN4-
S2} m/z: 525.1; observed m/z: 525.1. Other peaks, calc. for
[HgCl(LIII-NPrn-S)]+, m/z: 381.0, observed m/z: 381.0; calc. for
[Hg(LIII-NPrn-S)2-H], m/z: 489.1, observed m/z: 489.1.
Scheme 1. Synthesis of complexes.
reaction mixture was stirred for 2 h at room temperature and
a white precipitate was formed. To the precipitate was added

20
T.S. Lobana et al. / Polyhedron 87 (2015) 17–27
Table 2
1H NMR spectral data (d in ppm) of complexes 1–8.
–NH
Ring protons
–N-R
LI-NMe
LII-Net
LIII-NPrn
1a
5.7 sb
3.72 m (C4H), 3.57 (C5H)
3.65 m (C4,5H)
3.15 s (CH3)
6.02 sb
5.90 sb
8.42 sb
7.04 sb
7.75 sb
7.95 sb
7.45 sb
8.87 sb
9.07 sb
7.14 sb
3.65 m (N-CH2), 1.21 m (CH3)
3.65 m (N-CH2), 1.65 (CH2), 0.97 m (CH3)
3.57 m (N-CH2), 1.20 m (CH3)
3.14 m (CH3)
3.07 m (CH3)
3.61 q (N-CH2), 1.22 t (CH3)
3.09 m (CH3)
3.13 m (CH3)
3.48 m (N-CH2), 1.65 (CH2), 0.92 (CH3)
3.14 s (CH3)
3.65 m (C4H), 3.49 t (C5H)
3.72 m (C4,5H)
2b
3.73 m (C4,5H)
3b
3.67 m (C4,5H)
4a
3.76 m (C4,5H)
5b
3.69 m (C4,5H)
6c
3.86 m (C4H), 3.72 m (C5H)
3.78 m (C4,5H)
7a,d
8a
3.80 m (C4,5H)
a
b
c
CDCl3.
(CDCl3 + D6[DMSO]).
D6[DMSO].
d
N-Prn = N-CH2CH2CH3.
Fig. 1. ORTEP showing the molecular structure of [ZnCl2(LII-NEt)2] (1) and the intra
molecular H-bonding, SÁ Á ÁS distance (3.563 Å) (with 30% probability).
2.2.8. Synthesis of [HgI2(LI-NMe-S)2] (8)
Fig. 2. ORTEP showing the molecular structure of [ZnI2(LI-NMe)2] (2) and intra
molecular H bonding, SÁ Á ÁS distance (3.924 Å) (with 30% probability).
To
a
solution of 1-methyl-imidazolidine-2-thione (0.013 g,
solution of
0.112 mmol) in methanol (5 mL) was added
a
mercury(II) iodide (0.025 g, 0.055 mmol) in methanol (5 mL). The
reaction mixture was stirred for 2 h at room temperature. To this
mixture was added dichloromethane (5 mL) and slow evaporation
at room temperature formed pale yellow crystals of 8 (71%, m.p
103–105 °C). Anal. Calc. for C8H14HgI2N4S2: C, 14.03; H, 2.06; N,
8.18. Found: C, 13.85; H, 2.20; N, 8.10%. IR bands (KBr, cmÀ1):
and 3) diffractometers, equipped with a graphite monochromator
and Mo
K
a
(k = 0.71073 Å; 2–8,) and Cu
Ka radiation
(k = 1.54184 Å; 1). The unit cell dimensions and intensity data
were measured at 173(2) K for 1, 4, 6, 7 and 8, 295(2) K for 5 and
at 296(2) K for 2 and 3. The data were processed with CRYSALISPRO
(data collection, cell refinement) (1, 4–8), CRYSALISRED (data reduc-
tion) (1, 4, 6 and 8), CRYSALISPRO (data reduction) (5 and 7) [45], Bru-
ker APEX2 (data collection) and Bruker SAINT (cell refinement, data
reduction) (2 and 3) [46]. The structures were solved by direct
methods using the programs SHELXS97 [47] (1, 4–8) and SIR-92 (2
and 3) [48], and refined by full-matrix least-squares techniques
against F2 using SHELXL-97 [49]. The crystallographic data are given
in Table 1, while detailed bond lengths/angles are available in the
Supplementary material. The asymmetric unit of compound 4
contains one half-molecule situated on a twofold rotational axis
centered on the cadmium atom. Disorder is modeled for both
m(N–H) 3313 s;
m(C–H) 2917 m, 2887 m, 2792 w; m(C–C) +
m
(C–N) + d(C–H) 1540 s, 1504 s, 1468 s, 1401 m; 1328 s, 1298 s,
1286 s, 1194 s;
m
(C–S) 1111 s; 1022 m, 954 m, 633 s, 504 s. 1H
NMR data (CDCl3 , d ppm): 7.14 (s, 2H, NH), 3.80 (m, 8H, C4,5H),
3.14 (s, 6H, CH3).
2.3. X-ray crystallography
The single crystals of the compounds were mounted on glass
fibers and data were collected using Xcalibur, Eos, Gemini (1, 4,
6, 7 and 8), Xcalibur, Ruby, Gemini (5) and Bruker APEX-II CCD (2
Table 3
Important bond lengths (Å) and angles (°) of complexes 1–8.
M
X
N–R
M–X
M–S
C–S
S–M–S (X–M–X)
M–S–C
Zn (1)
Zn (2)
Cd (3)
Cd (4)
Cd (5)
Hg (6)
Hg (7)
Hg (8)
Cl
I
Br
Br
I
Cl
Cl
I
Et
2.2517(7), 2.2531(7)
2.5962(4), 2.5964(4)
2.5695(5), 2.5780(5)
2.5499(5)
2.7494(6), 2.7511(6)
2.5372(8), 2.5161(7)
2.5105(8), 2.5104(8)
2.7466(4), 2.7634(3)
2.3703(7), 2.3657(7)
2.3495(8), 2.3653(8)
2.5438(12), 2.5224(12)
2.5464(11)
2.5409(17), 2.5538(18)
2.4782(8), 2.4985(9)
2.5001(8), 2.5001(8)
2.5376(14), 2.5655(16)
1.715(3), 1.713(3)
1.699(3), 1.717(3)
1.716(4), 1.701(4)
1.694(3)
1.697(6), 1.714(7)
1.719(3), 1.718(3)
1.715(3)
97.58(3) [110.60(3)]
110.44(9), 109.84(9)
108.72(9), 96.65(9)
106.29(13), 94.18(13)
110.22(13)
107.40(19), 94.7(2)
105.96(12), 105.98(11)
106.21(11)
Me
Me
Et
Me
Me
Prn
Me
112.63(4) [113.432(13)]
114.23(5) [116.036(19)]
103.47(7) [111.74(3)]
111.61(7) [114.99(2)]
119.18(3) [102.43(3)]
112.32(4) [107.26(4)]
110.68(6) [114.306(13)]
1.701(5), 1.711(6)
105.89(18)

T.S. Lobana et al. / Polyhedron 87 (2015) 17–27
21
Fig. 6. ORTEP showing the molecular structure of [HgCl2(LI-NMe)2] (6) (with 50%
probability).
Fig. 3. ORTEP showing the molecular structure of [CdBr2(LI-NMe)2] (3) and intra
molecular H-bonding, SÁ Á ÁS distance (4.254 Å) (with 50% probability).
Fig. 7. ORTEP showing the molecular structure of [HgCl2(LIII-NPrn)2] (7) and intra
molecular H-bonding, (with 50% probability).
Fig. 4. ORTEP showing the molecular structure of [CdBr2(LII-NEt)2] (4), SÁ Á ÁS
distance (3.998 Å) (with 30% probability).
Fig. 5. ORTEP diagram showing the molecular structure of [CdI2(LI-NMe)2] (5) (with
30% probability).
carbon atoms of the ethyl group over two sites with an occupancy
ratio of 0.544(6):0.456(6). No classical hydrogen bonds are
observed. Complexes 2 and 3 are isostructural.
Fig. 8. ORTEP showing the molecular structure of [HgI2(LI-NMe)2] (8) (with 50%
probability).
3. Results and discussion
and LIII-NPrn , 1–8). On addition of a metal salt to a solution of
the thio ligand in methanol, followed by stirring, there was either
formation of a white precipitate (2, 3, 6 and 7) or no precipitation
(1, 4, 5 and 8). To the reaction mixture dichloromethane was added
and the clear solution obtained was allowed to crystallize at room
3.1. Comments on the synthesis
Scheme 1 shows the formation of complexes of ZnII, CdII and
HgII with the stoichiometry [MX2(L-NR)2] (L-NR = LI-NMe, LII-NEt

22
T.S. Lobana et al. / Polyhedron 87 (2015) 17–27
Table 4
3.2. Spectroscopy
N–HÁ Á ÁX distances (Å) and angles (°) for complexes 1–8.
The IR spectra of the complexes were different from those of the
Complex No.
d(HÁ Á ÁX)
2.394, 2.365
2.856
2.678
2.512
2.909
2.644, 2.585
2.389
d(NÁ Á ÁX)
3.196, 3.195
3.643
3.483
3.355
3.711
3.259, 3.254
3.262
\(N–HÁ Á ÁX)
155.38, 162.31
152.97
167.64
163.46
156.05
167.07, 169.69
170.66
ligands. For example, in complex 1, the m(N–H) band appeared at
1. Cl
2. I
3. Br
4. Br
5. I
6. Cl
7. Cl
8. I
3244 cmÀ1, which is in a higher energy region relative to the unco-
ordinated ligand (LII-NEt, 3188 cmÀ1). Other complexes showed
m
m
(N–H) bands in the region 3219–3313 cmÀ1. The characteristic
(C–S) band in complex 1 appears at 1127 cmÀ1, which is in a lower
energy region relative to the free thio ligand (1199 cmÀ1). Other
complexes showed m
(C–S) bands in the region 1111–1127 cmÀ1
2.875
3.676
152.00
(see Section 2). The proton NMR spectra of the complexes clearly
showed that the NH protons are most sensitive to coordination
(Table 2). For example, the free ligand LI-NMe shows the NH proton
signal at d = 5.70 ppm, and this is shifted to the low field region
7.04–8.87 ppm in its complexes 2, 3, 5, 6 and 8. Similarly, the NH
proton signals of LII-NEt and LIII-NPrn at 6.02 and 5.90 ppm respec-
tively are shifted to the low energy region 7.95–9.07 ppm in com-
plexes 1, 4 and 7. The N–R protons are not much affected and only
Note: aThe ortep diagrams of complexes 1, 2, 3, 5 and 7 depict N–HÁ Á ÁX distances
(Figs. 1–5), while ortep diagrams of 4, 6 and 8 do not show such distances and they
are calculated from their diagrams prepared using the mercury program (see
Supplementary data).
temperature. In this way, eight compounds were prepared which
formed crystals and their molecular structures were determined
using X-ray crystallography.
Fig. 9. Conformations of complexes 1–8.
Fig. 10. H-bonded 2D polymeric network of [ZnCl2(LII-NEt)2] (1).

T.S. Lobana et al. / Polyhedron 87 (2015) 17–27
23
Fig. 11. H-bonded 2D polymeric network of [ZnI2(LI-NMe)2] (2).
small changes occurred for the N–Me and N–CH2 protons. The ring
protons appeared as multiplets and are marginally affected in
complexes 1–8.
S, 110.71(2)°; Cl–Zn–Cl, 114.59(2)°} observed in the analogous
complex [ZnCl2(LI-NMe-S)2] [37]. The difference is attributed to
the effect of the substituents at one nitrogen atom of the thio ligand.
The bonding pattern of the complex [ZnI2(LI-NMe-S)2] (2) (Fig. 2) is
similar to that of complex 1. While the Zn–S distances are similar,
the S–Zn–S angle of 112.65(4)° is larger, as compared to that of
complex 1. The difference is attributed to the closer SÁ Á ÁS distance
(3.563 Å) in complex 1 vis-à-vis that in complex 2 (3.924 Å). The
Zn–S, Zn–Cl and Zn–I distances {Zn–I, 2.5961(4), 2.5964(4) Å} are
3.3. Molecular structures
The crystal data of complexes 1–8 are given in Table 1. Com-
plexes 1–6 and 8 crystallized in the monoclinic system with each
having space group P21/c, except for complex 4 with the space
group C2/c, and complex 7 crystallized in the trigonal system with
the space group R-3c. In the complex [ZnCl2(LII-NEt-S)2] (1) (Fig. 1),
ZnII is bonded to two chlorine atoms at Zn–Cl distances of 2.2517(7)
and 2.2531(7) Å, and to two S atoms at Zn–S distances of 2.3703(7)
and 2.3657(7) Å (Table 3). These distances are similar to those
observed in the literature [37]. The S–Zn–S and Cl–Zn–Cl angles
of 97.58(3) and 110.60(3)° respectively are less than those {S–Zn–
less than the corresponding sum of the ionic radii {Zn2+ and S2À
,
2.58; Zn2+ and ClÀ, 2.55; Zn2+ and IÀ, 2.94 Å} [50]. The molecular
structures of complexes 3–8 (Figs. 3–8) are similar to that of com-
plex 1. The Cd–S distances (complexes 3–5) lie in the range
2.5224(12)–2.5538(18) Å, which are comparable to the literature
trends [36]. Similarly, the Hg–S distances (complexes 6–8) lie in
the range 2.4782(8)–2.5660(16) Å, which are comparable to the
Fig. 12. H-bonded 2D polymeric network of [HgCl2(LI-NMe)2] (6).

24
T.S. Lobana et al. / Polyhedron 87 (2015) 17–27
Fig. 13. H-bonded 1D polymeric network of [HgCl2(LIII-NPrn)2] (7).
[M]+ → [M-X]+ (1-7)→[M-X-L]+ (6,7) →[M-H-X2]+ (6,7)
Scheme 2. Fragmentation steps, [M]+ = molecular ion.
and conformation IV (7). Each of complexes 1, 6 and 7 have differ-
ent intermolecular interactions, while complexes 2–5 and 8 have
the same type of intermolecular interactions. These conformations
give rise to four types of intermolecular interactions which result
in the formation of 2D (1–6, 8) or 1D (7) polymeric networks. These
networks are delineated in Figs. 10–13.
In the case of complex 1, the sulfur atom of the imidazole ring of
one molecule interacts with the CH hydrogen atom of imidazole
ring of second molecule through C–HÁ Á ÁS, and CÁ Á ÁS interactions
{C–HÁ Á ÁS, 2.922 Å, CÁ Á ÁS 3.875 Å; C–HÁ Á ÁS angle 166.93°} resulting
in the formation of a 1D chain. The CÁ Á ÁS distance is greater than
the sum of the van der Waals radii of carbon and sulfur, 3.45–
3.50 Å [50]. The C–H hydrogen atom of the imidazole ring in one
linear chain forms a H-bond with the chlorine atom {C–HÁ Á ÁCl,
2.794 Å; C–HÁ Á ÁCl, 154.54°}, of a second chain, resulting in the for-
mation of a 2D polymer (Fig. 10).
literature trends [36,40]. In the Cd/Hg complexes, the S–M–S and
X–M–S angles lie in the wide range 103.45(7)–119.18(3)°. In com-
plex 1, the C–S bond distance of 1.715(3) Å lies between C–S single
(1.81 Å) and C–S double (1.62 Å) bond distance values, indicating
partial double bond character [51] and the weakening of the bond
is due to the coordination of the ligand to ZnII. Similar behavior is
observed in complexes 2–8, and here the C–S bond distances fall
in the wide range 1.696(3)–1.721(4) Å. It is noted that the C–S dis-
tances do not vary in a systematic manner, either with respect to
the halogen or the metal atom.
3.4. Intra- and intermolecular interactions
In complex 2, the intermolecular interaction between the imino
hydrogen and iodine atom of a second molecule {NHÁ Á ÁI, 2.905 Å;
N–HÁ Á ÁI angle, 162.43°} leads to the formation of a 1D polymeric
chain. These chains further interact with each other through
C–HÁ Á ÁI interactions between the CH hydrogen atom of the imidaz-
ole ring and an iodine atom of a second chain {C–HÁ Á ÁI, 3.125 Å;
C–HÁ Á ÁI angle, 155.16°}, resulting in the formation of a 2D network
(Fig. 11). The interactions in complexes 3 and 5 and are similar (see
Supplementary data). In complex 6, the intermolecular hydrogen
bonding interaction between the N–CH3 hydrogen of the imidazole
ring and the chlorine atom of a second molecule {CHÁ Á ÁCl, 2.851 Å;
C–HÁ Á ÁCl angle, 126.68°} leads to the formation of a 1D polymeric
In complexes 1–8, there is intra molecular N–HÁ Á ÁX (X = Cl, Br, I)
hydrogen bonding. The N–HÁ Á ÁX, NÁ Á ÁX distances and N–HÁ Á ÁX
angles are given in Table 4. The NÁ Á ÁCl, NÁ Á ÁBr and NÁ Á ÁI distances
lie in the ranges 3.195–3.262, 3.483–3.355 and 3.643–3.711 Å
respectively. These distances are either less than or close to the
sum of the van der Waals radii of N and X {nitrogen and chlo-
rine = 3.25–3.45 Å, nitrogen and bromine = 3.35–3.55 Å and nitro-
gen and iodine = 3.50–3.67 Å} [50].
Fig. 9 shows the conformations adopted by the complex
molecules. Interestingly there are four types of conformations:
conformation I (1), conformation II (2–5, 8), conformation III (6),
Intens.
[%]
100
50
0
359
360
361
362
363
364
365
366
367
m/z
[%]
100
50
0
358
359
360
361
362
363
364
365
366
367
368 m/z
Fig. 14. Observed peak m/z = 359.0 and its isotropic pattern m/z 359.0, [MÀCl]+, C10H20ClN4S2Zn (1).

T.S. Lobana et al. / Polyhedron 87 (2015) 17–27
25
Intens.
[%]
15
10
5
0
421
422
423
424
425
426
427
m/z
m/z
[%]
100
50
0
421
422
423
424
425
426
427
428
429
Fig. 15. Observed peak m/z = 423.20 and its isotropic pattern m/z 424.9, [MÀBr]+ , C8H16BrN4S2Cd (3).
Intens.
[%]
100
50
0
464
465
466
467
468
469
470
471
472
473
m/z
m/z
[%]
100
50
0
465
466
467
468
469
470
471
472
Fig. 16. Observed peak m/z = 469.0 and its isotropic pattern m/z 469.0, [MÀCl]+, C8H16ClN4S2Hg (6).
Intens.
[%]
40
30
20
10
0
348
350
352
354
356
358
m/z
m/z
[%]
100
50
0
349
350
351
352
353
354
355
356
Fig. 17. Observed peak m/z = 353.0 and its isotropic pattern m/z 353.0, [MÀClÀ(LI-NMe)]+ C4H8ClN2SHg (6).

26
T.S. Lobana et al. / Polyhedron 87 (2015) 17–27
Intens.
[%]
10
5
0
428
429
430
431
432
433
434
435
436
m/z
m/z
[%]
100
50
0
428
429
430
431
432
433
434
435
436
Fig. 18. Observed peak m/z = 433.0 and its isotropic pattern m/z 433.0, [MÀHÀCl2]+, C8H15N4S2Hg (6).
chain. These chains further interact with each other through
C–HÁ Á ÁCl interactions between the CH hydrogen atom of the imid-
azole ring and the chlorine atom of a second chain {C–HÁ Á ÁCl,
2.858 Å; C–HÁ Á ÁCl angle, 140.24°}, resulting in the formation of a
2D network (Fig. 12). The packing diagram of complex 7 shows that
the sulfur atom of the imidazole ring in one molecule interacts
with the C atom of imidazole ring of a second molecule through
{CÁ Á ÁS 3.431 Å} interactions and the CH hydrogen atom of a ligand
in one linear chain forms an H-bond with the chlorine atom
{C–HÁ Á ÁCl, 2.900 Å; C–HÁ Á ÁCl, 165.33°} of a second molecule, result-
ing in the formation of a 1D polymeric chain (Fig. 13). The CÁ Á ÁS
distance is marginally less than the sum of the van der Waals radii
of carbon and sulfur, 3.45–3.50 Å [50].
India, Emeritus Grant [21(0904)/12-EMR-II] to T.S. Lobana, New
Delhi are gratefully acknowledged.
Appendix A. Supplementary data
CCDC 1007794–1007801 contain the supplementary crystallo-
graphic data for complexes 1–8. 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. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/
10.1016/j.poly.2014.10.016.
3.5. ESI-mass
References
An ESI mass spectral study of the complexes did not shown the
molecular ion, [M]+, but all the complexes (1–7) on which this
study was carried out have shown prominent peaks corresponding
to [MÀX]+ ions (here X represents a halogen). Complexes 6 and 7
showed additional peaks corresponding to [MÀXÀL]+ (L is the
neutral thio ligand) and [MÀHÀX2]+ species. Scheme 2 shows the
formation of the various species. Representative ESI-mass signals
are shown in Figs. 14–18.
[1] E.S. Raper, Coord. Chem. Rev. 153 (1996) 199.
[2] E.S. Raper, Coord. Chem. Rev. 129 (1994) 91.
[3] E.S. Raper, Coord. Chem. Rev. 165 (1997) 475.
[4] J.A. Garcia-Vazquez, J. Romero, A. Sousa, Coord. Chem. Rev. 193 (1999) 691.
[5] P.D. Akrivos, Coord. Chem. Rev. 213 (2001) 181.
[6] A. Kaltzoglou, P.J. Cox, P. Aslanidis, Inorg. Chim. Acta 358 (2005) 3048.
[7] A.J. Blake, V. Lippolis, T. Pivetta, G. Verani, Acta Crystallogr., Sect. C: Cryst.
Struct. Commun. 63 (2007) m364.
[8] T.S. Lobana, R. Sharma, G. Hundal, R.J. Butcher, Inorg. Chem. 45 (2006) 9402.
[9] T.S. Lobana, R. Sharma, R. Sharma, S. Mehra, A. Castineiras, P. Turner, Inorg.
Chem. 44 (2005) 1914.
[10] T.S. Lobana, R. Sharma, R.J. Butcher, Polyhedron 27 (2008) 1375.
[11] R. Sultana, T.S. Lobana, R. Sharma, A. Castineiras, T. Akitsu, K. Yahagi, Y. Aritake,
Inorg. Chim. Acta 363 (2010) 3432.
[12] T.S. Lobana, R. Sultana, R.J. Butcher, J.P. Jasinski, J.A. Golen, A. Castineiras, K.
Propper, F.J. Fernandez, M. Cristina Vega, J. Organomet. Chem. 745–746 (2013)
460.
[13] T.S. Lobana, R. Sultana, R.J. Butcher, J.P. Jasinski, T. Akitsu, Z. Anorg. Allg. Chem.
640 (2014) 1688.
[14] T.S. Lobana, R. Sultana, A. Castineiras, R.J. Butcher, Inorg. Chim. Acta 362 (2009)
5265.
[15] T.S. Lobana, R. Sultana, G. Hundal, R.J. Butcher, Dalton Trans. 39 (2010) 7870.
[16] T.S. Lobana, R. Sultana, R.J. Butcher, A. Castineiras, T. Akitsu, F.J. Fernandez,
M.C. Vega, Eur. J. Inorg. Chem. (2013) 5161.
[17] F. Noreen, T. Ruffer, H. Lang, A.A. Isab, S. Ahmad, J. Chem. Cryst. 38 (2008) 765.
[18] Q. Zhu, W. Chu, R. Huang, J. Zhang, Y. Xu, J. Coord. Chem. 61 (2008) 3390.
[19] G.A. Bowmaker, J.V. Hanna, C. Pakawatchai, B.W. Skelton, Y. Thanyasirikul, A.H.
White, Inorg. Chem. 48 (2009) 350.
[20] E.S. Raper, J.R. Creighton, J.D. Wilson, W. Clegg, A. Milne, Inorg. Chim. Acta 155
(1989) 85.
[21] G.A. Bowmaker, J.V. Hanna, B.W. Skelton, A.H. White, Chem. Commun. (2009)
2168.
4. Conclusion
Substituted imidazolidine-2-thiones with divalent metal ions,
Zn–Hg, have formed distorted tetrahedral complexes. The complex
molecules adopt four types of conformations which give rise to dif-
ferent patterns of intermolecular interactions and hence 2D (1–6,
8) or 1D (7) polymeric networks are obtained. ESI-mass has shown
that a halogen is easily lost and thus complexes 1–7 displayed
molecular ions with the loss of one halogen in each case, viz.,
[MÀX]+ ions. This reveals that the M–S bonds are quite strong
and the thio ligands remain bonded to the metal ions. In complexes
6 and 7, further loss of both halogens gave [MÀ(L2-H)]+ ions. In
addition, these two complexes also formed, [MÀXÀL]+ ions by
losing one halogen and one thio ligand from their respective
molecular ions.
[22] D. Jia, Y. Zhang, J. Deng, M. Ji, J. Coord. Chem. 60 (2007) 833.
[23] C. Palivan, T. Berclaz, M. Geoffroy, S. Ramaprabhu, G. Bernardinelli, J. Chem.
Soc., Faraday Trans. 91 (1995) 2155.
[24] L.P. Battaglia, A.B. Corradi, F.A. Devillanova, G. Verani, Transition Met. Chem. 4
(1979) 264.
Acknowledgments
Financial assistance from UGC (BSR), New Delhi – India and the
Council of Scientific and Industrial Research (CSIR), New Delhi –

T.S. Lobana et al. / Polyhedron 87 (2015) 17–27
27
[25] S. Ramaprabhu, E.A.C. Lucken, G. Bernardinelli, J. Chem. Soc., Dalton Trans.
(1995) 115.
[40] M. Cannas, F.A. Devillanova, G. Marongiu, G. Verani, J. Inorg. Nucl. Chem. 43
(1981) 2383.
[26] S. Ramaprabhu, E.A.C. Lucken, G. Bernardinelli, J. Chem. Soc., Dalton Trans.
(1993) 1185.
[27] M.S. Hussain, A.R. Al-Arfaj, M.L. Hossain, Transition Met. Chem. 15 (1990) 264.
[28] S. Friedrichs, P.G. Jones, Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 55
(1999) 1625.
[41] L. Cavalca, M. Nardelli, G. Fava, Acta Crystallogr. 13 (1960) 125.
[42] P.F. Rodesiler, N.G. Charles, E.A.H. Griffth, E.L. Amma, Acta Crystallogr., Sect. C:
Cyst. Struct. Commun. 43 (1987) 1058.
[43] T.S. Lobana, R. Sharma, R. Sharma, R. Sultana, R.J. Butcher, Z. Anorg. Allg. Chem.
634 (2008) 718.
[29] S. Friedrichs, P.G. Jones, Z. Naturforsch., B: Chem. Sci. 59 (2004) 49.
[30] S. Friedrichs, P.G. Jones, Z. Naturforsch., B: Chem. Sci. 59 (2004) 1429.
[31] S. Friedrichs, P.G. Jones, Z. Naturforsch., B: Chem. Sci. 59 (2004) 793.
[32] S. Friedrichs, P.G. Jones, Z. Naturforsch., B: Chem. Sci. 61 (2006) 1391.
[33] P.G. Jones, S. Friedrichs, Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 62
(2006) m623.
[34] A.R. Al-Arfaj, J.H. Reibenspies, A.A. Islab, M.S. Hussain, Acta Crystallogr., Sect. C
54 (1998) 51.
[35] L. Cavalca, P. Domiano, A. Musatti, P. Sgarabotto, J. Chem. Soc., Chem. Commun.
(1968) 1136.
[44] J.A. Garcia-Vazquez, A. Sousa-Pedrares, M. Carabel, J. Romero, A. Sousa,
Polyhedron 24 (2005) 2043.
[45] Oxford Diffraction. CrysAlisPro CCD and CrysAlisPro RED Oxford Diffraction
Ltd., Yarnton, England, 2009.
[46] Bruker, SMART and SAINT, Area Detector Control and Integration Software, Bruker
Analytical X-ray Instruments Inc., Madison, Wisconsin, USA, 1997.
[47] G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008) 112.
[48] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, J. Appl. Crystallogr. 26
(1993) 343.
[49] G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Structures,
University of Goettingen, Germany, 1997.
[50] J.E. Huheey, E.A. Keiter, R.L. Keiter, Inorganic Principals of Structure and
reactivity, fourth ed., Harper Collins College Publishers, New York, 1993.
[51] L. Pauling, The Nature of the Chemical Bond, third ed., Cornell University Press,
New York, 1960.
[36] M.I.M. Wazeer, A.A. Isab, M. Fettouhi, Polyhedron 26 (2007) 1725.
[37] M. Fettouhi, M.I.M. Wazeer, A.A. Isab, J. Coord. Chem. 60 (2007) 369.
[38] M. Fettouhi, M.I.M. Wazeer, A.A. Isab, Z. Kristallogr. New Cryst. Struct. 221
(2006) 221.
[39] C. Nardelli, Gazz. Chim. Ital. 88 (1958) 248.