Synthesis and characterisation of some N-alkyl/aryl and N,N′-dialkyl/aryl thiourea cadmium(II) complexes: The single crystal X-ray structures of [CdCl2(CS(NH2) NHCH3)2]n and [CdCl2(CS(NH2)NHCH2 CH3)2]

Article abstract of DOI:10.1016/S0277-5387(02)01420-1

A series of cadmium(II) complexes with N-alkyl or aryl and N,N′-dialkyl or diaryl thioureas (RNHCSNHR′; where R = R′ = CH₃, CH₂CH₃, C₆H₅ and or R′ = H) have been synthesised and characterised. The structures of the polymer [CdCl₂(CS(NH₂) NHCH₃)₂]_n (I) and monomer [CdCl₂(CS(NH₂)NHCH₂CH)₂] (II) were determined by single crystal X-ray methods. The structure (I) is a polymer chain built from [CdCl₃S₃] distorted octahedra. Complex II is monomeric with a distorted tetrahedral geometry at the cadmium centre. ¹H NMR spectroscopy in deuterated dimethyl sulfoxide at room temperature had broadened NH peaks in the lower field (region 6.0-10.0 ppm) which indicates the presence of both cis and trans-isomers for the N-alkylthioureas. All the spectroscopic data obtained are consistent with the coordination of ligands by sulphur atom to the metal ion. Thermogravimetric studies show that several of these complexes decompose cleanly to CdS and may be useful in materials preparation.

Full text of DOI:10.1016/S0277-5387(02)01420-1

Polyhedron 22 (2003) 595ꢁ603
/
www.elsevier.com/locate/poly
Synthesis and characterisation of some N-alkyl/aryl and N,N?-
dialkyl/aryl thiourea cadmium(II) complexes: the single crystal X-ray
structures of [CdCl2(CS(NH2)NHCH3)2]n and
[CdCl2(CS(NH2)NHCH2CH3)2]
M.J. Moloto a, M.A. Malik b, P. O’Brien b,*, M. Motevalli c, G.A. Kolawole a
a Department of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa 3886, South Africa
b Department of Chemistry and Materials Science, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
c Department of Chemistry, Queen Mary and Westfield College, Mile End Road, London, E1 4NS, UK
Received 15 October 2002; accepted 3 December 2002
Abstract
A series of cadmium(II) complexes with N-alkyl or aryl and N,N?-dialkyl or diaryl thioureas (RNHCSNHR?; where Rꢀ
/
R?ꢀ
/
CH3, CH2CH3, C6H5 and or R?ꢀH) have been synthesised and characterised. The structures of the polymer
/
[CdCl2(CS(NH2)NHCH3)2]n (I) and monomer [CdCl2(CS(NH2)NHCH2CH)2] (II) were determined by single crystal X-ray
methods. The structure (I) is a polymer chain built from [CdCl3S3] distorted octahedra. Complex II is monomeric with a distorted
1
tetrahedral geometry at the cadmium centre. H NMR spectroscopy in deuterated dimethyl sulfoxide at room temperature had
broadened NH peaks in the lower field (region 6.0ꢁ10.0 ppm) which indicates the presence of both cis and trans-isomers for the N-
/
alkylthioureas. All the spectroscopic data obtained are consistent with the coordination of ligands by sulphur atom to the metal ion.
Thermogravimetric studies show that several of these complexes decompose cleanly to CdS and may be useful in materials
preparation.
# 2003 Elsevier Science Ltd. All rights reserved.
Keywords: N-Alkylthiourea; Cadmium(II) complexes; Synthesis; X-ray structures
1. Introduction
of the CÃ
/
S group and the nitrogen atom of the NH,
R?ꢀalkyl or aryl
NHR or NRR? groups (where Rꢀ
/
/
The chemistry of substituted thiourea derivatives has
attracted attention because of their potential use as
reagents for the separation of metal ions [1] and in
biological applications such as their use: as antibacterial
[2,3], antiviral [4] or antifungal agents [5,6]. In addition
to their applications, the ligands are of interest as they
possess various potential donor sites: the sulphur atom
groups). Several studies have been made on the co-
ordinating ability of these ligands mainly with aim of
determining the coordination mode. The N-alkyl sub-
stituted thiourea, with the coplanar N2CS skeletal atoms
can take two possible conformational forms, trans and
cis whereas three different conformations are possible
for N,N?-dialkyl substituted thioureas the cisꢁ
transꢁtrans and cisꢁtrans isomers (Fig. 1). NMR
studies have been in efforts to determine the extent of
CN bond in thioureas [7ꢁ10].
/
cis,
/
/
* Corresponding author. Address: Department of Chemistry,
Manchester University, Oxford Road, Manchester, M13 9PL, UK.
the rotation about the SÄ
/
/
A number of studies on the structural conformation
of N-methylthiourea have been carried out, both in the
Tel.: ꢂ
/
44-161-275-4653; fax: ꢂ
/
44-161-275-4616.
E-mail address: paul.obrien@man.ac.uk (P. O’Brien).
0277-5387/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0277-5387(02)01420-1

596
M.J. Moloto et al. / Polyhedron 22 (2003) 595ꢁ603
/
Fig. 1. Structure of substituted thiourea showing delocalisation of the p-bond (a) and conformational isomers for both mono and disubstituted alkyl/
aryl thiourea (b).
solid state and solution [11ꢁ
/
13]. It was confirmed by
report the X-ray structural analysis of the two com-
plexes and the infrared and NMR spectra of the
cadmium(II) complexes of the N-methyl-, N-ethyl-, N-
phenylthiourea and their N,N?-disubstituted analogues.
Mido et al. [14] through Raman and IR and X-ray
structural analyses of N-methylthiourea that the com-
pound assumes the cis configuration (Fig. 1) in the solid
state. Lane et al. [11] studied the infrared spectra of
several thiourea derivatives in the solid state. They
found that N,N?-dimethylthiourea and N,N?-
2. Experimental
diethylthiourea were transꢁtrans isomers. Subsequent
/
studies on the coordination of these molecules were
made using infrared spectra to determine their binding
2.1. Materials and instrumentation
sites [11,15ꢁ22]. In most complexes they bind through
/
Cadmium chloride, N-methylthiourea, N-ethyl-
thiourea, N-phenylthiourea, N,N?-dimethylthiourea,
N,N?-diethylthiourea, N,N?-diphenylthiourea obtained
from Aldrich, were used as purchased. Ethanol (analy-
tical grade) was used without further purification. X-ray
data was collected on an Enraf Nonius CAD-4 diffract-
ometer. Microanalysis was performed on a CARLO
ERBA elemental analyser for C, H, N, S while for Cd a
Horizon ICP Fisons elemental analyser was used.
the sulphur atom although there are examples of
complexes with N-bonded alkylthiourea derivatives
[23]. The cadmium(II) and copper(I) complexes show
marked similarity in their structures in that they form
clusters [24], dinuclear [25] or polynuclear complexes
[26,27] whereas other complexes are monomeric [21,22].
There is a substantial downshift in the vibrational
frequencies of CÄ/S bond when coordinated to a metal,
suggesting considerable interactions between the
thiourea molecules and the metals [15].
Infrared spectra were recorded on FT-IR PerkinꢁElmer
/
Paragon 1000 spectrophotometer as nujol mulls. NMR
spectra were recorded on a Varian Associates Inova
spectrometer (400 and 300 MHz). Thermogravimetric
and differential thermal analysis (TGA and DTA) were
performed up to 800 8C on Shimadzu analysers TGA-
50 and DTA-50 with nitrogen flow and heating rate of
Thiourea has also been used in the deposition of CdS
thin films from aqueous solutions [28]. In this work our
interest lies in studying the binding of the substituted
thiourea molecules to cadmium through sulphur atom
of the CS group as such compounds could be used as
precursors in the preparation of CdS nanoparticles. We
10 8C minꢃ1
.

M.J. Moloto et al. / Polyhedron 22 (2003) 595ꢁ
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603
597
2.2. Preparation of the complexes
2.6. CdCl2(CS(NHCH3)2)2 (IV)
All compounds were prepared using a similar meth-
ods as outlined below.
Yield 98% m.p. 203 8C Anal. Calc. C, 18.4; H, 4.1; N,
14.3; S, 16.4; Cd, 28.7. Found: C, 18.4; H 4.1; N 14.3; S
16.4; Cd 28.9. IR (nujol mull) cmꢃ1: 3286(vs), 3045(w),
1592(vs), 1536(vs), 1308(s), 1190(m), 1150(m), 1040(s),
1023(m), 721(s), 673(m), 569(s), 546(s), 445(w). 1H
NMR (d, DMSO-d6) ppm: 7.53 (br, 4H, NH), 2.78
(br, s, 12H, CH3). 13C{1H} NMR (d, DMSO-d6) ppm:
181.75 (s, CS); 31.07 (s, CH3).
2.3. [CdCl2(CS(NH2)NHCH3)2]n (I)
In a typical experiment a hot solution of N-
methylthiourea (0.150 g, 1.66 mmol) in ethanol (10 ml)
was added into a heated solution of cadmium chloride
(0.153 g, 0.83 mmol) in ethanol (15 ml). The mixture was
stirred and refluxed for 2 h. The colourless solution was
filtered to remove any traces of unreacted materials
while hot and was left in an open beaker at room
temperature to crystallise by slow evaporation. Trans-
parent cubic crystals were obtained after 24 h. The
product was filtered, washed twice with ethanol and
dried under vacuum. Yield 55.6% m.p. 233 8C Anal.
Calc. C, 13.2; H, 3.3; N, 15.4; S, 17.6; Cd, 30.9 Found:
C, 13.3; H 3.3; N 15.0; S 16.9; Cd 31.3. IR (nujol mull)
cmꢃ1: 3342(m), 3293(m), 3195(m), 3140(m), 2925(vs),
2854(s), 1676(sh), 1625(vs), 1573(vs), 1488(w), 1462(s),
1417(m), 1303(m), 1172(m), 1144(m), 991(vw), 779(m),
720(m), 618(w), 579(w), 532(m), 489(m), 361(s). 1H
NMR (d, DMSO-d6) ppm: 7.78, 7.48 and 6.95 (br,
NH, NH2); 2.80 and 2.64 (br, CH3). 13C{1H} NMR (d,
DMSO-d6) ppm: 183.73 and 179.90 (s, CS); 30.85 and
29.73 (s, CH3).
2.7. CdCl2(CS(NHC6H5)2)2 (V)
Yield 91% m.p. 198 8C Anal. Calc. C, 48.8; H, 3.8; N,
8.8; S, 10.0; Cd, 17.6. Found: C, 48.8; H 3.8; N 8.8; S
10.0; Cd 17.6. IR (nujol mull) cmꢃ1: 3333(m), 3162(m),
1614(sh), 1593(s), 1543(vs), 1508(s), 1313(w), 1295(m),
1249(m), 1129(vs), 1073(w), 1024(w), 1003(w), 941(s),
899(w), 761(s), 725(m), 690(vs), 633(m), 601(s), 508(m),
473(w). 1H NMR (d, DMSO-d6) ppm: 9.79 (s, 4H, NH);
7.48 (d, 4H, C6H5); 7.32 (t, 4H, C6H5); 7.11 (t, 2H,
C6H5). 13C{1H} NMR (d, DMSO-d6) ppm: 179.38 (s,
CS); 139.29, 128.30, 124.29 and 123.38 (s, C6H5).
2.8. CdCl2(CS(NHCH2CH3)2)2 (VI)
Yield N.A. m.p. 204 8C Anal. Calc. C, 26.8; H, 5.4;
N, 12.5; S, 14.4; Cd, 25.1. Found: C, 27.0; H 5.6; N 12.5;
S 15.4; Cd 26.7. IR (nujol mull) cmꢃ1: 3342(m),
3312(w), 3198(m), 3159(s), 1650(vs), 1583(s), 1529(s),
1477(m), 1308(m), 1092(s), 808(s), 785(m), 758(m),
2.4. CdCl2(CS(NH2)NHCH2CH3)2 (II)
1
Yield 67% m.p. 201 8C Anal. Calc. C, 18.4; H, 4.1; N,
14.3; S, 16.4; Cd, 28.7. Found: C, 18.4; H 4.1; N 14.3; S
16.4; Cd 28.9. IR (nujol mull) cmꢃ1: 3348(m), 3302(w),
3241(m), 3164(s), 1643(s), 1573(vs), 1569(s), 1497(sh),
1317(s), 1109(s), 1011(m), 815(w), 779(w), 718(m),
692(w), 627(m), 562(w), 485(m). H NMR (d, DMSO-
d6) ppm: 7.36 (br, NH); 3.32 (br, 8H, CH2); 1.04 (t, 12H,
CH3). 13C{1H} NMR (d, DMSO-d6) ppm: 182.76 (s,
CS); 43.83 (s, CH2) and 19.59 (s, CH3).
1
689(m), 625(m), 567(w), 485(s). H NMR (d, DMSO-
2.9. Crystallography
d6) ppm: 8.09, 7.61 and 6.96 (br, NH, NH2); 3.06 (br,
4H, CH2); 1.03 (t, 6H, CH3). 13C{1H} NMR (d,
DMSO-d6) ppm: 182.32 and 176.64 (s, CS); 38.86 (s,
CH2) 14.89 and 13.97 (s, CH3).
The intensity data were collected on a CAD-4
˚
0.71069 A)
diffractometer and Mo Ka radiation (lꢀ
/
using v ꢁ
determined by least-squares refinement on diffract-
ometer angles [I, 10.9380u 012.888, II, 9.0680u 0
/
2u scan. The unit cell parameters were
2.5. CdCl2(CS(NH2)NHC6H5)2 (III)
/
/
/
/
12.988] for 25 automatically centred reflections [29].
All data were corrected for Lorentz-polarization effects
by XCAD4 [30] and for absorption by semi-empirical
methods (c scan) [31]. The structure was solved by
Patterson method using DIRDIF-99,[32] and refined
anisotropically (non-hydrogen atoms) by full-matrix
least-squares on F2 using SHELXL-97 [33] program. The
H atoms were calculated geometrically and refined with
a riding model. The program ORTEP-3 [34] PLATON [35]
was used for drawing the molecules. WINGX [36] used to
prepare material for publication. Experimental data is
given in Table 2.
Yield 94% m.p. 210 8C Anal. Calc. C, 34.5; H, 3.3; N,
11.5; S, 13.2; Cd, 23.1. Found: C, 35.1; H 3.4; N 11.7; S
13.4; Cd 23.5. IR (nujol mull) cmꢃ1: 3418(m), 3388(m),
3295(s), 3201(s), 1621(vs), 1596(m), 1544(s), 1490(s),
1456(s), 1320(m), 1272(m), 1191(m), 1062(w), 912(w),
857(vw), 792(m), 756(s), 721(s), 692(s), 633(m), 597(s),
1
562(s), 492(s), 447(w). H NMR (d, DMSO-d6) ppm:
9.78 (s, 6H, NH, NH2); 7.47 (d, 4H, C6H5); 7.31 (t, 4H,
C6H5); 7.11 (t, 2H, C6H5). 13C{1H} NMR (d, DMSO-
d6) ppm: 179.38 (s, CS); 139.29, 128.30, 124.29 and
123.38 (s, C6H5).

598
M.J. Moloto et al. / Polyhedron 22 (2003) 595ꢁ603
/
2.10. X-ray diffraction
Table 1
Selected IR data for N-alkyl- and N,N?-dialkylthiourea complexes
X-ray diffraction patterns on powdered samples were
measured on Phillips X’Pert materials research diffract-
Complex
Vibrational modes (wave numbers, cmꢃ1
)
nCÄSꢂnCÃ pCÄ nCÄ nCÃN
/
/
/
N
/
S
/
S
/
ometer using secondary graphite monochromated Cu
˚
1.54060 A) at 40 kV/50 mA. Samples
were supported on glass slides. Measurements were
taken using a glancing angle of incidence detector at
Ka radiation (lꢀ
/
I
779
718
756
721
758
761
618
625
633
569
627
633
489
485
492
546
485
473
1557, 1298,
1149
II
1573, 1569,
1317, 1011
an angle of 28, for 2u values over 208ꢁ608 in steps of
/
0.058 with a scan speed of 0.0182u sꢃ1
.
III
IV
VI
V
1621, 1596,
1544, 1320, 1062
1592, 1536,
1308, 1190
3. Results and discussion
1583, 1529,
1477, 1308, 1092
1614, 1593,
1543, 1249, 1073
A series of substituted thiourea cadmium(II) com-
plexes were prepared by first reacting alkylthioureas and
cadmium chloride (2:1 mole ratio), in hot ethanol,
followed by reflux. The products were obtained as air
stable colourless to white crystals, formed upon con-
centrating the solution at room temperature. The
analytical and spectroscopic data are consistent with
the proposed formulation of the complexes. Their
melting points suggest that they are monomers in
general which ranges from 198 to 210 8C, in contrast
polymeric [CdCl2(CS(NH2)NHCH3)2]n, melts at
233 8C.
with the nitrogen atoms, either neighbouring or directly
bonded to them. This observation is consistent with
studies of these compounds by variable temperature
NMR [10]. At higher temperatures the peaks for the
substituted thioureas become well resolved, whereas at
lower temperatures there is broadening and coalescence
of the peaks associated with NH. This effect is
attributed to the slow rotation around the SÄ
at low temperature and it appears that only two of the
three possible rotational isomers of N,N?-
/CN bond
diethylthiourea are present, namely the cisꢁ/cis and the
4. Spectroscopic studies
cisꢁtrans [7]. The transꢁtrans isomer is not detectable,
/
/
probably due to the steric interaction between the two
trans-ethyl groups. The low-energy barrier to free
Mido et al. [14] and Matsuura and co-workers [17]
were able to confirm from their spectral observations
and the single crystal X-ray structure analysis that the
N-methylthiourea molecule is in a cis form as opposed
to the trans form. There are a number of features that
relate to the binding of ligand molecules to the metal. In
rotation around the SÄ/CN bond in thioureas is evi-
denced by the low temperature at which different
isomers have different resonance frequencies due to
the competition between the two amide bonds for
electron delocalisation (Fig. 1(a)). There was further
evidence in NMR studies that the rotation about this
amide bond is either rapid or one isomer predominates
over the other [8]. However, resonances due to the cis
and trans rotational isomers have been reported for N-
methylthiourea molecule [9] with the methyl group cis to
the sulfur atom resonating at higher field compared to
the trans methyl.
[CdCl2(CS(NH2)NHCH3)2]n, the CÄ
/
S out-of-plane
bending mode (pCÄS) and its stretching vibrational
/
mode (nCÄ
/
S) shows a remarkable shifts from 636 and
495 cmꢃ1 to 618 and 489 cmꢃ1, respectively. The
vibrational mode (both stretching and bending) due to
the CÃ
/
N bond appear at 1557, 1298 and 1149 cmꢃ1 and
are shifted to 1573, 1303 and 1172 cmꢃ1, respectively in
the complex. The changes, which range from 5 to 20
1
cmꢃ1 are attributed to the weakening of the CÃ
/
N or CÄ
/
The H NMR spectra of both complexes I and II,
gave three broad peaks at low field (6.96ꢁ8.10 ppm) due
/
S bonds on coordination. The CS bond tends to loose its
double bond character whereas the CN bond gains
electron density raising its bond character. A similar
observation was made for all other complexes in their
IR spectra associated with CS and CN modes of
vibration (Table 1) consistent with the previously
reported data [11,18,20,22].
to the NH protons. Two broad signals at 2.80 and 2.64
ppm for the methyl groups in complex I were observed,
which coincide with the 13C{1H} NMR signals at 30.85
1
and 29.73 ppm. The two CH2 signals on the H NMR
spectrum of complex II appears at 3.31 and 3.06 ppm,
whereas one of the signals due to the carbon on CH2
group appears to have merged with the solvent peaks on
the 13C{1H} NMR spectrum while the second peak
appears at 38.36 ppm. The carbon atoms of the CS
group of complex I gave two signals at 183.73 and
The NMR spectra of complexes (IꢁVI) were recorded
/
at room temperature in deuterated dimethylsulfoxide
(CD3SOCD3) at 300 and 400 MHz. There is a collapse
in the multiplicity of the signals of protons associated

M.J. Moloto et al. / Polyhedron 22 (2003) 595ꢁ
/
603
599
1
Table 2
Crystal data and detailed structure refinement for complex I and II
were observed in both the H (7.53 ppm-NH and 2.78
ppm-CH3) and 13C{1H} (181.75 ppm-CS and 31.07
ppm-CH3) NMR spectra of complex IV. The NMR
results showed that there is a detectable amount of
trans-isomer in the N-alkylthiourea (complexes I and II
whereas no trans-isomer was detected for the ar-
ylthiourea complex III.
I
II
Empirical formula
Formula weight
Temperature (K)
C4H12CdCl2N4S2
363.60
160(2)
C6H16CdCl2N4S2
391.65
293(2)
˚
Wavelength (A)
0.71073
triclinic
P1
0.71073
triclinic
P1
Crystal system
Space group
Unit cell dimensions
5. X-ray studies
˚
a (A)
6.975(8)
9.162(8)
9.944(6)
71.97(6)
76.27(6)
69.75(8)
560.8(9)
2
8.547(7)
9.841(10)
9.902(10)
95.50(8)
114.44(6)
101.36(9)
728.6(12)
2
˚
b (A)
Details of the crystal data and structure refinements
are provided in Table 2. Selected bond distances and
bond angles of [CdCl2(CS(NH2)NHCH3)2]n (I) and
CdCl2(CS(NH2)NHCH2CH3)2 (II) are shown in Table
3. Figs. 2 and 3 shows the ORTEP diagrams of the two
complexes showing labelling of the non-hydrogen
atoms.
˚
c (A)
a (8)
b (8)
g (8)
3
˚
Volume (A )
Z
Density (calculated)
)
2.153
(Mg mꢃ3
Absorption coefficient 2.757
1.785
2.130
388
(mmꢃ1
F(000)
)
5.1. [CdCl2(CS(NH2)NHCH3)2]n (I)
356
0.50ꢄ
2.18ꢁ24.98
Crystal size (mm)
u Range for data
collection (8)
/
0.13ꢄ
/
0.05
0.40ꢄ
2.31ꢁ24.99
/
0.40ꢄ0.30
/
The structure of complex I (Fig. 2) comprises of a
polymeric chain with alternating bridging groups
through the two chlorides and sulphur atoms. The
cadmium ion in each unit, CdCl3S3, consists of three
/
/
Index ranges
00
100
110
2184
/
h 0
k 0
l 011
/
8,
ꢃ
/
100
00k 0
110l 0
2780
/
h 0
11,
11
/
9,
ꢃ
ꢃ/
/
/
/
10,
/
/
/
/
ꢃ/
/
/
CdÃ
bridging bonds and one non-bridging bond for each
type of ligand. The CdÃS bond distances are slightly
longer than for the corresponding dichloro bis(S-thiour-
/
Cl bonds and three CdÃ
/
S bonds. There are two
Reflections collected
Independent
reflections
1964 (Rint
ꢀ
/
0.0063)
2558 (Rint
ꢀ0.0080)
/
/
Completeness to u
99.5
99.7
˚ ˚
S; 2.517 A), which ranges from 2.632(2) A
for the terminal N-methylthiourea ligand to 2.744(2)
˚
and 2.789(4) A for the bridging ligands.
(24.988) (%)
Max/min transmission 0.8744 and 0.3394
ea)Cd (CdÃ
/
0.5675 and 0.4830
1.092
Goodness-of-fit on F2
Final R indices
1.055
R1ꢀ0.0201,
wR2ꢀ0.0537
R1ꢀ0.0236,
wR2ꢀ0.0553
0.0285(13)
/
R1ꢀ
wR2ꢀ
R1ꢀ0.0542,
wR2ꢀ0.1043
/
0.0378,
A similar observation was made for the CdÃ
/
Cl bond
/
/0.0968
˚
distances, which ranges from 2.576(2) A for the terminal
R indices (all data)
/
/
˚
chlorides and, 2.642(3) and 2.704(2) A for the bridging
/
/
Extinction coefficient
chloride ligands. In each monomer unit, the metal core
is constituted by three chloride and three N-
methylthiourea ligands. Hence the formulation of the
chemical structure, [CdCl2(CS(NH2)NHCH3)2]n. Sun et
al. [37] made similar observation in the bond distances
Largest difference peak 0.647 and ꢃ
/
0.769
1.837 and ꢃ0.593
/
ꢃ3
˚
and hole (e A
)
179.90 ppm on the 13C{1H} NMR spectrum, which were
close to those of complex I (182.32 and 176.64 ppm),
which is consistent with the presence of the two
rotational isomers, i.e. the cis and trans isomers in
of CdÃ
/
S in a mixed ligands cadmium(II) complex of
xanthic acid and N,N?-bis(4-methoxyphenyl)thiourea.
The xanthate chelating ligand has longer bond distances
1
˚
(2.831 A) for the bridging sulfur atoms and shorter
these N-alkylthiourea complexes I and II. Both the H
and 13C NMR spectra of complex III gave resonances,
which indicates the dominance of the cis isomer.
Similarly to the N,N?-dialkylthiourea complexes (IV
and VI), only a single broad signal was observed in the
˚
distances (2.606 A) for the non-bridging ones. The CÃ
/
S
and CÃ
methylthiourea ligand, 1.721(3) and 1.322(4) A (average
of C2ÃN3 and C2ÃN4), respectively, agrees with those
of thiourea molecules reported in the Cambridge
/
N
bond distances for the terminal
˚
/
/
1
lower field of the H NMR spectra.
The N-phenyl and N,N?-diphenylthiourea complexes
˚
Structural Database i.e. 1.726 (CÃ
/
S) and 1.322 A (CÃ
/
III and V gave similar peaks in both H and 13C{1H}
1
N). The additional CÃN bond due to the methyl
N bond
distances for the bridging methylthiourea ligands,
/
˚
NMR spectra; 9.78 (NH group) and a set of three peaks
at 7.47 (doublet), 7.31 (triplet) and 7.11 (triplet) (phenyl
group) and; 179.38 and 179.94 (CS group) and a set of
four signals at 139.3, 128.3, 124.3, 123.4 and 139.8,
128.9, 124.9, 124.1 (C6H5), respectively. Two signals
substituent is 1.451(4) A. The CÃ
/
S and CÃ
/
˚
1.738(3) and 1.315(4) A (average of C1Ã
N2), respectively, are within the expected range of bond
distances of thiourea molecules. The CÃN and CÃ
/
N1 and C1Ã
/
/
/
S

600
M.J. Moloto et al. / Polyhedron 22 (2003) 595ꢁ603
/
Table 3
bond angles are within the expected range of tetrahedral
geometry (varying from 118.5(2)8 to 122.7(3)8).
˚
Selected bond distances (A) and bond angles (8) for complex I and II
I
II
5.2. CdCl2(CS(NH2)NHCH2CH3)2 (II)
˚
Bond distances (A)
Cd(1)Ã
Cd(1)Ã
Cd(1)Ã
Cd(1)Ã
Cd(1)Ã
Cd(1)Ã
/
Cl(1)
Cl(2)
S(1)
2.576(2)
2.704(3)
Cd(1)Ã
/
Cl(3)
Cl(2)
S(3)
2.500(3)
2.455(3)
2.497(4)
2.519(3)
1.721(5)
1.738(7)
1.329(9)
1.402(9)
1.361(9)
1.312(7))
1.453(7)
1.312(7)
The structure of complex II and the packing diagram
are shown in Fig. 3(a) and (b), respectively. The
structure is based on a discrete monomeric molecule.
The coordination polyhedra around the Cd(II) ion is a
distorted tetrahedral. The two N-ethylthiourea ligands
are S-bonded to the metal atom. In this four coordinate
structure, molecular units are arranged so that one of
the chloride ion (Cl(3)) and the metal atom lie on a
crystallographic threefold axes which relates to the two
thiourea ligands and the second chlorine atom (Cl(2)).
/
Cd(1)Ã
/
/
2.7443(17) Cd(1)Ã
2.6324(17) Cd(1)Ã
/
/S(2)
/
S(4)
a
/Cl(2)
2.642(3)
2.789(4)
1.738(3)
1.721(3)
1.315(4)
1.323(4)
1.316(4)
1.452(2)
1.322(4)
1.450(4)
S(3)Ã
S(4)Ã
N(5)Ã
N(5)Ã
N(6)Ã
N(7)Ã
N(7)Ã
N(8)Ã
/
C(12)
b
/S(1)
/
C(9)
S(1)Ã
S(2)Ã
N(1)Ã
N(3)Ã
N(2)Ã
N(2)Ã
N(4)Ã
N(4)Ã
/
C(1)
/
C(9)
C(10)
C(9)
/
C(2)
/
/
C(1)
C(2)
C(1)
C(4)
C(2)
C(3)
/
/
/
C(12)
C(13)
C(12)
/
/
/
/
/
The S(3)Ã
/
Cd(1)Ã
/
S(4), S(4)Ã
/
Cd(1)Ã
/
Cl(2) and S(3)Ã
/
/
Cd(1)ÃCl(2) bond angles are 111.28(9)8, 112.82(9)8 and
/
Bond angles (8)
Cl(1)ÃCd(1)ÃCl(2)
S(1)ÃCd(1)ÃS(2)
Cl(2)Ã
S(1)ÃCd(1)Ã
S(2)ÃCd(1)Ã
Cl(1)Ã
Cl(2)Ã
Cl(1)Ã
Cl(1)Ã
S(2)ÃCd(1)Ã
S(2)Ã
S(2)Ã
S(1)Ã
S(1)Ã
113.84(10)8, respectively. These angles deviate consider-
ably from the regular tetrahedral value of 109.478, which
may be explained by the steric interaction between the
two ethyl groups. Intermolecular hydrogen bonding
interactions between the NH protons and both sulphide
and chloride ions of adjacent molecules stabilise the
a
/
/
171.88(2)
169.00(3)
172.78(2)
93.31(8)
97.65(7)
88.31(9)
83.86(9)
83.73(7)
95.78(6)
99.44(6)
122.7(2)
118.5(2)
121.9(2)
118.5(2)
Cl(2)Ã
S(3)ÃCd(1)Ã
Cl(2)ÃCd(1)Ã
Cl(2)ÃCd(1)Ã
Cl(3)ÃCd(1)Ã
Cl(3)ÃCd(1)Ã
Cd(1)Ã
Cd(1)Ã
S(3)ÃC(12)Ã
S(4)ÃC(9)ÃN(5)
N(5)ÃC(9)ÃN(6)
S(4)ÃC(9)ÃN(6)
S(3)ÃC(12)ÃN(7)
N(7)ÃC(12)ÃN(8)
/
Cd(1)Ã
/
Cl(3) 106.45(9)
/
/
/
/
S(4)
111.28(9)
113.84(10)
112.82(9)
107.74(11)
103.96(10)
106.5(2)
97.7(3)
b
/
Cd(1)Ã
/S(1)
/
/
S(3)
/
/
Cl(2)
/
/
S(4)
S(3)
S(4)
/
/
Cl(2)
/
/
/
Cd(1)Ã
Cd(1)Ã
Cd(1)Ã
Cd(1)Ã
/Cl(2)
/
/
a
/
/
Cl(2)
S(2)
S(1)
/
S(3)Ã
/
C(12)
molecular structure (Fig. 3(b)).
˚
S bonds (2.497(4) and 2.519(3) A) are shorter
/
/
/
S(4)Ã
/C(9)
The CdÃ
/
/
/
/
/
N(8)
122.2(4)
120.4(5)
117.7(6)
121.9(5)
117.5(4)
120.3(5)
a
than in the N-methylthiourea complex, which suggest
that the s-bond character of this bond is stronger. The
/
/
Cl(2)
/
/
/
C(2)Ã
C(2)Ã
C(1)Ã
C(1)Ã
/
N(3)
N(4)
N(1)
N(2)
/
/
/
/
/
/
/
/
/
/
/
/
/
/
Symmetry transformations used to generate equivalent atoms.
a
ꢃ
/
xꢂ
/
1,ꢃ
/
yꢂ
1,ꢃ
/
1,ꢃ
/
z.
b
ꢃx,ꢃ
/
/
yꢂ
/
/z.
bonds are intermediate between a single and double
bond but closer to a normal CÄ
/
N double bond distance
˚
(1.27 A) and a normal CÃ
/
S single bond distance (1.81
˚
A).
The coordination polyhedra around the Cd(II) ion is
a distorted octahedron. Three N-methylthiourea ligands
are S-bonded. The ClÃ
are lowered and increased from octahedral values.
Though trans ClÃCdÃCl, SÃCdÃS and ClÃCdÃ
/
CdÃ
/
Cl (8) and SÃ
/
CdÃS (8) angles
/
/
/
/
/
/
/S
bond angles are relatively close to 1808 (varying from
169.00(3)8 to 172.78(2)8). The cis bond angles around
the cadmium ions vary from 79.71(7)8 to 99.44(6)8. The
smallest angles (79.71(7)8 and 83.53(6)8) were observed
for the bridging S-bonded N-methylthiourea and chlo-
ride ligands, respectively, the other bond angles espe-
cially for the terminal ligands are hence slightly below or
above 908 and 1808. This forces the compound to
assume a zigzag pattern with the rectangular shaped
Cd2Cl2 bridge lying vertical and almost perpendicular to
the Cd2S2 bridge. The CdÃ
greater than the tetrahedral value, varying from
116.48(11)8 to 118.04(11)8. The SÃCÃN and NÃCÃ
/
SÃ
/
C bond angles are slightly
Fig. 2. (a) Polymeric structure and (b) and a parent molecular unit for
[CdCl2(CS(NH2)NHCH3)2]n (I).
/
/
/
/
N

M.J. Moloto et al. / Polyhedron 22 (2003) 595ꢁ
/
603
601
Fig. 3. Molecular structure (a) and packing diagram showing short contacts (b) for CdCl2(CS(NH2)NHCH2CH3)2 (II) (aꢀ
/
(ꢃ
/
x, ꢃ
/
y, ꢃ
/
z), bꢀ
/
(1ꢃ
/
x,1ꢃy,1ꢃz), cꢀ(ꢃx,ꢃy,1ꢃz), dꢀ(1ꢃx,ꢃy,1ꢃz)).
/
/
/
/
/
/
/
/
/
/
˚
˚
SÄ
to those observed in complex I. In both cases the CÃ
and SÃC bonds shows intermediate bond lengths
/
C (1.729(6) A) and NÃ
/
C (1.345(9) A) bonds are close
5.3. Thermal decomposition
The thermal decompositions of the complexes Iꢁ
/
N
/
VI
/
reported in this work were also studied by TGA and
DTA methods under inert and air atmosphere. The
residues obtained from these decompositions were
subjected to XRD analysis. The X-ray diffraction
patterns of the residues obtained from complex II are
shown in Fig. 5 and the data listed in Table 4. Under
nitrogen the complexes initially melt, the melts rapidly
between single and double bond, which is attributed to
the delocalisation of electron in the amide bond. N-
alkylthioureas can exist in two different configurations
where the thioamide hydrogen atom and the thiocarbo-
nyl bond are either in cis or trans form [38]. In the above
described N-alkylthiourea complexes each thiourea
ligand is in a cis form.

602
M.J. Moloto et al. / Polyhedron 22 (2003) 595ꢁ603
/
Table 4
Experimental XRD data of the residues from TGA analysis of
complex II
a
d(lit )/A
˚
˚
d(exp)/A
hkl
a (Nitrogen)
b (Air)
3.57
3.34
3.14
2.44
2.09
1.91
1.78
1.75
1.72
1.67
3.61
3.37
3.17
2.44
2.06
1.89
1.79
1.76
1.73
1.68
3.59
3.36
3.16
2.45
2.07
1.90
1.79
1.77
1.73
1.69
100
002
101
102
110
103
200
112
201
004
a
Ref 1999 JCPDS.
transform to a pale yellow solids. In air, the compounds
undergo similar changes at the start of decomposition,
but as the temperature is increased the yellow solid
changes further to orange and finally to dirty green,
probably due to partial metathesis to the oxide. The
TGA curves (Fig. 4) indicate that for each compound
the loss of weight starts around 200 8C and continues to
about 400 8C at which point most of the organic part of
the molecule and the chloride has been lost. A period of
slow loss of mass leads to the complete formation of
Fig. 5. XRD patterns of the residue obtained from thermal decom-
position of [CdCl2(CS(NH2)NHCH2CH3)2] (II), both under N2 (a)
atmosphere and in air (b) (*impurities) indexed to wurtzite CdS.
loss of mass above 600 8C. The X-ray diffraction
patterns of the residues obtained from complex II are
shown in Fig. 5 were studied in more detail as this
compound may have promise as a precursor. The
residues from under both air or nitrogen atmospheres
were analysed by X-ray diffraction methods (Fig. 5(a),
(b)) and showed patterns consistent with the predomi-
nantly of the wurtzite phase of CdS (Table 4). The only
difference between the two patterns is that the diffrac-
tion pattern in Fig. 5(a) is sharper and cleaner which
might be expected under nitrogen atmosphere whereas
the residue obtained under air shows is broader which
may reflect some oxide formation.
sulphide by 500ꢁ600 8C. The percentage mass loss is in
/
most cases close to that range expected for the stoichio-
metric formation of the sulfide as follows: Found (Calc.)
(%), (I) 36.7 (39.7), (II) 36.4 (36.9), (III) 35.9 (29.6), (IV)
36.4 (36.9), (V) 25.2 (22.6) and (VI) 31.4 (32.3). A variety
of factors confound this analysis cadmium sulfide itself
has appreciable volatility as evidenced by pronounced
We have not observed any exothermic process in our
DTA studies of these compound in contrast to the
results observed for copper, zinc and tin thiourea
complexes [39] in which cases the metal sulphides were
converted to their metal oxides. No such gross conver-
sion of cadmium sulfide to the oxide was observed
during the work reported in this study under air.
6. Conclusion
The structure of both complexes I and II indicates
that bonding of the N-alkylthiourea ligands is through
sulphur atom of the CS group. Complex I is a polymer
with alternating chloride and sulphur atoms bridging the
adjacent metal centres. Both ligands are in the cis
Fig. 4. TGA (under nitrogen) curves for [CdCl2(CS(NH2)NHCH3)2]n
(I), CdCl2(CS(NH2)NHCH2CH3)2 (II), CdCl2(CS(NH2)NHC6H5)2
(III), CdCl2(CS(NHCH3)2)2 (IV), CdCl2(CS(NHC6H5)2)2 (V),
CdCl2(CS(NHCH2CH3)2)2 (VI).

M.J. Moloto et al. / Polyhedron 22 (2003) 595ꢁ
/
603
603
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/
S and CÃ/N bond in the thioamide core on
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7. Supplementary data
Crystallographic supplementary data are available
from the CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK on request (deposit@ccdc.cam.ac.uk) quoting
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Acknowledgements
This work is supported by the National Research
Foundation (NRF) and Royal Society (UK). The work
was carried out in the laboratories of the Department of
Chemistry (University of Zululand) and laboratories of
P. O’Brien at the University of Manchester.
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