Metal dithiocarbamate precursors for the preparation of a binary sulfide and a pyrochlore: Synthesis, structure, continuous shape measure and bond valence sum analysis of antimony(III) dithiocarbamates

Article abstract of DOI:10.1016/j.poly.2014.09.028

The antimony(III) complexes [Sb(chmdtc)₃] (1), [Sb(chedtc)₃] (2) and [Sb(dchdtc)₃] 0.5 C₇H₈ (3) (where chmdtc = cyclohexylmethyldithiocarbamate, chedtc = cyclohexylethyldithiocarbamate and dchdtc = di

Full text of DOI:10.1016/j.poly.2014.09.028

Polyhedron 85 (2015) 598–606
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Metal dithiocarbamate precursors for the preparation of a binary sulfide
and a pyrochlore: Synthesis, structure, continuous shape measure and
bond valence sum analysis of antimony(III) dithiocarbamates
b
Subburayan Sivasekar a, Kuppukkannu Ramalingam a, , Corrado Rizzoli
⇑
a Department of Chemistry, Annamalai University, Annamalainagar 608 002, India
b Department of General and Inorganic Chemistry, University of Parma, Parma 43100, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
The antimony(III) complexes [Sb(chmdtc)3] (1), [Sb(chedtc)3] (2) and [Sb(dchdtc)3] 0.5 C7H8 (3) (where
chmdtc = cyclohexylmethyldithiocarbamate, chedtc = cyclohexylethyldithiocarbamate and dchdtc = dic-
yclohexyldithiocarbamate) have been prepared and characterized by electronic, IR and NMR (1H and
13C) spectra and single crystal X-ray diffraction. Electronic spectra of the complexes show charge transfer
transitions. The characteristic thioureide bands occur at 1468, 1479 and 1445 cmꢀ1 for (1), (2) and (3)
respectively. The single crystal X-ray structures of (1), (2) and (3) reveal anisobidentate binding of the
dithiocarbamates. Short CAHꢁ ꢁ ꢁS contacts are observed along the ‘a’ axis in (2) and (3). CShM calculations
on the SbS6 chromophores support the distorted octahedral geometry in (1) and (2), and the distorted
pentagonal pyramidal geometry in (3), clearly quantifying the extent of deviation from the ideal geom-
etries. The nature of the substituents and the lone pair of electrons present in antimony are responsible
Received 28 June 2014
Accepted 10 September 2014
Available online 5 October 2014
Keywords:
Antimony(III)
Dithiocarbamate
Pyrochlore
Crystal structures
Nanosulfide
for the shift of the metal atom position from the geometrical center of the six sulfur atoms. BVS of the
3+
compounds show the highly covalent nature of the SbAS bonds. Nano Sb2S3 and (Tl+2/3ꢀ2d)[Tl Sb3+
]
y
1ꢀy
Sb2O6O01/3ꢀd, a pyrochlore, have been prepared from the precursors and have been characterized by PXRD,
FESEM, EDX, HRTEM and SAED.
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
metal dithiolates have persisted for over three decades because of
their applications and academic diversity. Simple dithiocarbamate
Molecular single source precursors of new materials for various
applications have the advantage of containing all the elements nec-
essary for the formation of the final solid material [1]. Most semi-
conductor devices are prepared from volatile and ultra-pure
gaseous derivatives of various organic and inorganic precursors
as starting materials. Metal dithiolates, dithiobiurets, diketonates
and alkoxides, like many other metallo-organic compounds, have
been used as precursors for many new materials which have inter-
esting optical and electronic properties [2–7]. Research interests in
salts have shown interesting biological and pharmacological prop-
erties [8–11]. Relatively, the chemistry of 1,1-dithiochelates of
main group elements is less widely explored than that of the tran-
sition metals [12]. Dithiocarbamates show a variety of coordina-
tion modes such as isobidentate, anisobidentate, monodentate
and triconnective [13]. Metal dithiolates in particular have been
used as single source precursors in CVD and other related tech-
niques for the preparation of thin films of semiconductor materials
in the recent past [2,14–17].
In particular, Group XV dithiolates continue to attract attention
due to their diverse applications in agriculture, industry, medicine
⇑
Corresponding author. Tel.: +91 413 2202834; fax: +91 414 422265.
E-mail address: krauchem@yahoo.com (K. Ramalingam).
http://dx.doi.org/10.1016/j.poly.2014.09.028
0277-5387/Ó 2014 Elsevier Ltd. All rights reserved.

S. Sivasekar et al. / Polyhedron 85 (2015) 598–606
599
and nanotechnology [18,19]. Antimony(III) chalcogenides, Sb2X3,
where X = S and Se, show excellent photoconductivity, semicon-
ducting properties and are potential candidates for applications
in solar energy conversion. Intelligent experimental procedures
adopted for the preparation of the chalcogenides result in the
desired morphologies [20–22]. Attempts have been made to iden-
tify new pyrochlore phases involving TlASbAO oxide because of
their potential applications [23,24]. In continuation of our interest
in the identification of new materials using metallodithiolates as
precursors, in this paper we report the synthesis and character-
ization of three precursors, viz. [Sb(chmdtc)3] (1), [Sb(chedtc)3]
(2) and [Sb(dchdtc)3] 0.5 C7H8 (3) (where chmdtc = cyclohexyl-
methyldithiocarbamate, chedtc = cyclohexylethyldithiocarbamate
and dchdtc = dicyclohexyldithiocarbamate anions).
ice-cold conditions (5 °C) to obtain a yellow dithiocarbamic acid
solution. To the freshly prepared dithiocarbamic acid solution, an
acidified solution of Sb2O3 (0.01 mol, 2.915 g) was added with con-
stant stirring. A yellow solid separated from the solution, which
was filtered, washed with ethanol and dried in air. Yield: 83%,
m.p.: 173 °C. Anal. Calc. for C24H42N3S6Sb (686.8): C, 41.97; H,
6.16; N, 6.11. Found: C, 41.92; H, 6.12; N, 6.07%.
2.2.2. Preparation of tris(cylohexylethyldithiocarbamato)antimony
(III); [Sb(chedtc)3] (2)
N-cyclohexyl-N-ethylamine (0.03 mol, 4.49 mL) and carbon
disulfide (0.03 mol, ꢂ5 mL) in methanol (20 mL) were mixed under
ice-cold conditions (5 °C) to form a yellow solution of dithiocarba-
mic acid. A weakly acidified solution of Sb2O3 (0.01 mol; 2.915 g)
was then added with continuous stirring. A similar procedure as
described in Section 2.2.1 was used for the preparation. A pale
yellow precipitate was obtained, which was washed with metha-
nol and then dried in air. Yield: 78%, m.p.: 153 °C. Anal. Calc. for
C27H48N3S6Sb (728.8): C, 44.49; H, 6.64; N, 5.77. Found: C, 44.45;
H, 6.61; N, 5.72%.
Nano antimony(III) sulfide, and (Tl+2/3ꢀ2d)[Tl13ꢀ+ ySb3+y]Sb2O6O01/3ꢀd
,
2.2.3. Preparation of tris(dicylohexyldithiocarbamato)antimony(III);
[Sb(dchdtc)3] 0.5 C7H8 (3)
a pyrochlore, were prepared and characterized by powder XRD, FESEM,
EDX, HRTEM and SAED analysis.
A similar procedure as described in Section 2.2.1 was employed
for the preparation of the dicyclohexylamine analogue. N,N-dicy-
clohexylamine (0.03 mol, 3.66 mL), carbon disulfide (0.03 mol,
ꢂ5 mL) in methanol (20 mL) and Sb2O3 (0.01 mol, 2.915 g) were
used for the preparation. Yield: 82%, m.p. 265 °C. Anal. Calc. for
2. Experimental
Antimony trioxide (SD fine chemicals, India), the parent amines,
carbon disulfide (Fisher Scientific, India) and the solvents (SD fine
chemicals, India) were commercially available analytical grade
materials and were used as supplied without further purification.
Melting/boiling points of the products were determined with a
digital apparatus (Jains, India). Elemental analyses were carried
out with an Elementar, Vario Micro Cube instrument. IR spectra
were recorded on an Avatar Nicolet FT-IR spectrometer (range
4000–400 cmꢀ1) as KBr pellets of the compounds. Electronic spectra
were recorded in CH2Cl2 on a Hitachi U-2001 double beam spec-
trometer. Thermal analysis was carried out with a NETZSCH STA
449F3 instrument under a nitrogen atmosphere with a heating rate
C42.50H70N3S6Sb (937.2): C, 54.47; H, 7.53; N, 4.48. Found: C,
54.43; H, 7.49; N, 4.44%.
All three compounds were recrystallized from toluene and only
compound (3) showed the presence of stoichiometric toluene of
crystallization.
2.2.4. Preparation of tris(cylohexylmethyldithiocarbamato)
thallium(III); [Tl(chmdtc)3]
Tris(cylohexylmethyldithiocarbamato)thallium(III), [Tl(chmdtc)3],
was prepared as per the procedure reported earlier from this
laboratory [30].
of 20 K minꢀ1 1H and 13C NMR spectra were recorded on a Bruker
.
AMX-400 spectrometer at room temperature using CDCl3 as the
solvent. The powder diffraction data were collected in the 2h range
2°–80° using a Bruker-D8 X-ray diffractometer equipped with Cu
2.2.5. Preparation of nano Sb2S3 by the non-conventional solvothermal
decomposition of tris(disubstituted dithiocarbamato)antimony(III)
1 mM of the tris(disubstituted dithiocarbamato)antimony(III)
complexes (1), (2) and (3) as clear solutions in chloroform
(100 mL) were heated with diethylenetriamine (2 mL) at 60 °C
for 45 min. Solid yellow antimony sulfide was separated from chlo-
roform, washed with ether and dried in air.
Karadiation at a fixed current and potential. The scan speed and step
sizes were 0.05° minꢀ1 and 0.00657 respectively. FE scanning
electron micrographs of the samples were recorded with a JEOL
JSM-5610Lv microscope. HRTEM measurements were carried out
on a JEOL 2100 (Field emission) with an accelerating voltage of
200 kV.
2.2.6. Preparation of (Tl+2/3ꢀ2d)[Tl31+ꢀySb3+y]Sb2O6O01/3ꢀd pyrochlore
(Tl+2/3ꢀ2d)[Tl13+ꢀySb3+y]Sb2O6O01/3ꢀd pyrochlore was prepared by
mixing finely ground recrystallized samples of [Sb(chmdtc)3]
(1 mmol, 0.69 g) and [Tl(chmdtc)3] (1 mmol, 0.77 g) in a pestle and
mortar which were then ground again thoroughly to obtain an inti-
mate fine powder of a 1:1 mixture of the dithiocarbamates. The mix-
ture was then loaded into a platinum crucible and heated in a
furnace in air. Three samples of the above were heated at 295, 350
and 750 °C and subsequently characterized.
2.1. X-ray crystallography
Intensity data were collected at ambient temperature (295 K)
on a Bruker APEX-II CCD diffractometer with graphite monochro-
mated Mo Ka radiation (k = 0.71073 Å) and were corrected for
absorptions with a multi-scan technique [25–27]. The structures
were solved by direct methods using SIR97 and were refined by
SHELX97 [28]. The non-hydrogen atoms were refined anisotropically
and all the hydrogen atoms were fixed geometrically. Molecular
plots were obtained using the ORTEP-3 program [29].
3. Results and discussion
2.2. Preparation of the complexes, nano Sb2S3 and pyrochlore
3.1. Infrared spectral studies
2.2.1. Preparation of tris(cylohexylmethyldithiocarbamato)
antimony(III); [Sb(chmdtc)3] (1)
Some important infrared spectral bands are presented in
N-cyclohexyl-N-methylamine (0.03 mol, 3.96 mL) and carbon
disulfide (0.03 mol, ꢂ5 mL) in methanol (20 mL) were mixed under
Table 1. For complexes (1), (2) and (3), the
mCAN (thioureide) bands
are observed at 1468, 1479 and 1445 cmꢀ1, respectively. The mCAS

600
S. Sivasekar et al. / Polyhedron 85 (2015) 598–606
14.32 ppm as a much shielded signal and a0-C(H2) appears to be
highly deshielded at 43.66 ppm. The -C(H) signal of the cyclo-
hexyl ring appears at 63.13 ppm. The b- , - and d- carbon signals,
Table 1
Electronic and IR spectral data.
a
IR (cmꢀ1
)
c
Compound
UV–Vis (nm)
which are the least affected by complexation, appear at 30.60 and
between 25.40 and 25.64 ppm respectively.
CT
Intraligand
mCAN
mCAS
mCAH
[Sb(chmdtc)3] (1)
[Sb(chedtc)3] (2)
[Sb(dchdtc)3] (3)
442
443
439
340
342
358
1468
1479
1445
1001
1009
1006
2849–2928
2851–2928
2851–2924
In the case of complex (3), the a-CH proton of the cyclohexyl
ring is observed at 5.16 ppm. The b- , c- and d-CH2 signals appear
in the region 1.79–1.82(e) ppm (collapsed). The 13C NMR spectrum
exhibits a weak characteristic signal due to the thioureide carbon
stretching bands are observed around 1000 cmꢀ1, supporting [31]
the bidentate coordination mode of the dithiocarbamate ligand
to the metal center. However, the single crystal X-ray structures
of the compounds show the anisobidentate nature of bonding of
the dithiocarbamates. The mCAH bands are observed in the range
at 199.95 ppm. The 13C NMR signal corresponding to the
a
-C(H)
carbon of the cyclohexyl ring is found to be significantly shielded
and appears at 65.71 ppm. The b-C(H2) and -C(H2) carbons appear
c
in the regions 25.03–29.78 and 26.32–34.51 ppm. The NMR spectra
of the complexes clearly indicate that the immediate environment
around the thioureide nitrogen is largely affected upon complex
formation. The alkyl groups are non-equivalent in the complexes
2849–2928 cmꢀ1
.
as the
a
, b and
c
-methylene protons and terminal methyl protons
substantial barrier to
3.2. Electronic spectra
result in broad signals, indicating
a
CAN < bond rotation. The prominent deshielding of the ACH2 pro-
tons in the compounds is attributed to the shift of electron density
Electronic spectra of the compounds (Table 1.) show bands
between 340 and 358 nm due to intraligand
mainly associated with the NAC@S and SAC@S groups [32,33].
The charge transfer transitions, which impart the characteristic
color to the compounds, are observed in the range 439–443 nm.
p–
p⁄ transitions,
on the sulfur atom (or the metal) through the thioureide
p system.
In a similar manner, the -methylene protons adjacent to the nitro-
a
gen atom undergo strong deshielding and are observed in the
region 3.80–3.81 ppm. The b-CH2 signals are observed in the range
1.48–1.95 ppm and assignments are made on the basis of proton
integral values obtained for the corresponding signals. The thioure-
ide signals observed in the compounds are mostly similar, except
in the case of [Sb(dchdtc)3] (3), which has a signal slightly higher
than the other two compounds, indicating an increased contribu-
tion of the thioureide form in [Sb(dchdtc)3] (3).
3.3. NMR spectral studies
The NMR spectral data of the antimony complexes are listed in
Table 2. The chemical shifts reported in the spectral database for
organic compounds (SDBS) for the parent amines are shown in
brackets [34]. The 1H NMR spectrum of complex (1) shows an
intense signal at 4.92 ppm, corresponding to single proton integra-
tion, due to the
tons (a0-CH3) attached to the nitrogen appear at 3.28(s) ppm
with a proton integration corresponding to three. The -CH and
a
-CH proton of the cyclohexyl ring. The CH3 pro-
3.4. Thermogravimetric analysis
a
Thermal analyses of the compounds were carried out under a
nitrogen atmosphere. [Sb(chmdtc)3] (1) showed a large single step
mass loss, observed in the range 280–310 °C. The residue stabilized
at 540 °C corresponds to Sb2S3 (Exptl.: 26.0%; Calcd.: 26.7%).
[Sb(chedtc)3] (2) showed a similar pattern of mass loss, with a sin-
gle step thermal decay at temperatures <500 °C. The final residue
confirmed the formation of Sb2S3 (Exptl.: 23.0%; Calcd.: 23.2%).
[Sb(dchdtc)3] 0.5 C7H8 (3) showed loss toluene, the solvent of crys-
tallization, (Exptl.: 5.0%; Calcd.: 5.0%) up to 240 °C. The bulk of the
mass was lost on continued heating to a temperature of 510 °C and
the residue perfectly agreed with the mass expected for Sb2S3
(Exptl.: 18.0%; Calcd.: 18.1%). The thermal analysis confirmed the
proposed formulae of the compounds perfectly. The most impor-
tant observation is that in all three compounds the final residue
was found to be Sb2S3. Among the three compounds, the dicyclo-
analogue [Sb(dchdtc)3] 0.5 C7H8 (3) showed a relatively higher
thermal stability.
a0-CH3 protons are affected to a maximum extent on complexation.
In the cyclohexyl ring all the equatorial protons are deshielded to a
large extent compared to the axial protons. The equatorial protons
appear in the range 1.80–1.88 ppm. The axial protons appear
between 1.66 and 1.69 ppm. The 13C NMR spectrum of (1) shows
a weak signal at 199.41 ppm due to the thioureide carbon [35].
The
and the a0-C(H3) carbon atom appears at 35.43 ppm. The b-,
- and d- carbon signals are the least affected and appear at
a-carbon atom of the cyclohexyl ring appears at 62.60 ppm
c
25.35, 25.45 and 29.93 ppm respectively.
In complex (2), the 1H NMR signal for the
a-CH proton of the
cyclohexyl ring appears at 4.95 ppm and a0-CH2 appears at 3.80–
3.81 ppm, corresponding to two protons. The b0-CH3 protons of
the ethyl group appears as a well resolved triplet at 1.29–
1.38 ppm. The 13C NMR spectrum of (2) shows a characteristic
thioureide signal at 199.38 ppm. The b0-CH3 signal appears at
Table 2
NMR spectral data (ppm).
Complex
NMR
1H
a
-CH
c
-CH2 & d-CH2
CH3/CH2 (alkyl)
3.28 (2.42)
N13CS2
–
[Sb(chmdtc)3] (1)
4.92 (2.30)
1.80–1.88(e)
1.66–1.69
29.93 25.35,
25.45
1.80–1.95(e)
1.58–1.69
30.60
25.40–25.64
1.78–1.81(e)
1.25–1.60 (collapsed)
29.70
13C
1H
62.60 (58.63)
4.95
35.43
199.41
–
3.80–3.81
1.29–1.38
43.66
14.32
–
[Sb(chedtc)3] (2)
[Sb(dchdtc)3] (3)
13C
1H
63.13
199.38
–
5.16 (2.55)
65.71 (53.17)
13C
–
199.95
25.33–26.68

S. Sivasekar et al. / Polyhedron 85 (2015) 598–606
601
Table 3
Crystal data, data collection and refinement parameters for [Sb(chmdtc)3], [Sb(chedtc)3] and [Sb(dchdtc)3] 0.5 C7H8.
Complex
[Sb(mchdtc)3]
[Sb(chedtc)3]
[Sb(dchdtc)3] 0.5 C7H8
Empirical formula
Formula weight
Color
C24H42N3S6Sb
686.72
yellow
C27H48N3 S6Sb
728.79
yellow
C42.50H70N3S6Sb
1874.39
yellow
Habit
block
block
block
Crystal system
Space group
Crystal dimension (mm3)
a (Å)
b (Å)
c (Å)
hexagonal
P 63
triclinic
P1
monoclinic
P 21/c
ꢀ
0.25 ꢃ 0.18 ꢃ 0.14
13.8776(6)
13.8776(6)
9.4649(4)
90.00
90.00
120.00
1578.61(18)
2
1.445
0.35 ꢃ 0.20 ꢃ 0.19
10.1061(3)
12.2458(3)
14.5676(4)
78.5810(10)
84.8840(10)
81.5590(10)
1744.66(8)
2
0.33 ꢃ 0.26 ꢃ 0.21
12.1780(8)
14.0520(10)
28.7180(19)
90.00
100.6135(11)
90.00
4830.3(6)
2
a
(°)
b (°)
c
(°)
U (Å3)
Z
Dcalc (g cmꢀ3
F (000)
k (Å)
)
1.387
756
1.289
1972
Mo Ka (0.71073)
708
Mo K
a
(0.71073)
Mo Ka
(0.71073)
h range (°)
Scan type
Index range
Reflections collected
Reflections [Fo > 2 (Fo)]
Weighting scheme
1.69–30.66
multi
1.71–25.00
multi
1.44–25.25
multi
ꢀ19 6 h 6 19; ꢀ19 6 k 6 19; ꢀ13 6 l 6 13 ꢀ12 6 h 6 11; ꢀ14 6 k 6 14; ꢀ15 6 l 6 17 ꢀ14 6 h 6 14; ꢀ16 6 k 6 16; ꢀ34 6 l 6 34
3252
3133
5975
5308
8757
7504
r
w = 1/[s2(F2o) + (0.0265P)2]
where P = (F2o + 2Fc2)/3
w = 1/[s2(F2o) + (0.0212P)2 + 1.100P]
w = 1/[s2(F2o) + (0.0373P)2 + 2.7376P]
where P = (F2o + 2Fc2)/3
334
where P = (F2o + 2Fc2)/3
459
Number of parameters refined 104
Final R, Rw (obs, data)
Goodness-of-fit (GOF)
0.0167, 0.0421
1.043
0.0238, 0.0537
1.007
0.0282, 0.0726
1.036
Table 4
Selected bond distances (Å) and bond angles (°).
[Sb(chmdtc)3]
[Sb(chedtc)3]
[Sb(dchdtc)3] 0.5 C7H8
Bond distances
SbAS(1)
SbAS(2)
2.5251(4)
2.9732 (4)
1.6988(13)
1.7493(13)
1.3297(17)
1.462(2)
SbAS(1)
SbAS(2)
SbAS(3)
SbAS(4)
SbAS(5)
SbAS(6)
S(1)AC(1)
S(2)AC(1)
N(1)AC(1)
2.5411(6)
2.8483(8)
2.5331(5)
2.9513(6)
2.5511(7)
2.9962(6)
1.697(2)
1.750(2)
Sb(1)AS(1)
Sb(1)AS(2)
Sb(1)AS(3)
Sb(1)AS(4)
Sb(1)AS(5)
Sb(1)AS(6)
S(1)AC(1)
S(2)AC(1)
N(1)AC(1)
2.6683(7)
2.7856(7)
2.4557(7)
2.8853(7)
2.6228(7)
2.8571(7)
1.745(3)
1.708(3)
1.331(3)
S(1)AC(1)
S(2)AC(1)
C(1)AN(1)
C(2)AN(1)
C(3)AN(1)
1.4833(18)
1.327(3)
Bond angles
S(1)ASbAS(2)
S(1)AC(1)AS(2)
N(1)AC(1)AS(1)
N(1)AC(1)AS(2)
C(1)AN(1)AC(2)
C(1)AN(1)AC(3)
64.71(3)
S(1)ASbAS(2)
S(3)ASbAS(4)
S(5)ASbAS(6)
S(1)AC(1)AS(2)
S(3)AC(10)AS(4)
S(5)AC(19)AS(6)
66.46(2)
64.85(2)
64.16(2)
118.63(14)
118.74(14)
118.78(14)
S(1)ASb(1)AS(2)
S(3)ASb(1)AS(4)
S(5)ASb(1)AS(6)
S(1)AC(1)AS(2)
S(3)AC(14)AS(4)
S(5)AC(27)AS(6)
64.76(2)
66.09(2)
64.55(2)
115.66(14)
116.19(15)
116.52(16)
118.67(10)
122.99(10)
118.34(10)
121.60(10)
120.91(12)
3.5. Structural analysis
sulfur atoms. The SbAS bonds show the anisobidentate binding
of the dithiocarbamate ligand (SbAS: 2.5331(5)–2.9962(6) Å). The
mean thioureide CAN distance was found to be 1.330(1) Å, which
indicates it has partial double bond character. The sulfur atom is
involved in a supramolecular interaction with the hydrogen atom
of the next molecule at a distance of 2.706 Å (S(1)ꢁ ꢁ ꢁH(7A); the
sum of the van der Waals radii is 3.0 Å). In (2), antimony lies below
the plane of the sulfur atoms (S1/S3/S5/S6: r.m.s. 0.3171; maxi-
mum deviation 0.2162 Å for S5). The coordination geometry in
[Sb(dchdtc)3] (3) is a distorted pentagonal pyramid. In (3), the
SbAS distances are in the range 2.4557(7)–2.8853(7) Å, indicating
anisobidentate binding of the dithiocarbamate ligand. The mean
thioureide distance in the compound is 1.331(3) Å. A number of
short contacts, such as H(9B)ꢁ ꢁ ꢁSb: 2.964 Å (the sum of the van
der Waals radii is 3.46 Å), S(3)ꢁ ꢁ ꢁH(32A): 2.844 Å, H(7A)ꢁ ꢁ ꢁC(30):
Crystal data, data collection and refinement parameters are
given in Table 3. Selected bond parameters are given in Table 4.
ORTEP diagrams of (1), (2) and (3) are shown in Figs. 1–3 respec-
tively. In [Sb(chmdtc)3] (1), two formula units are present in the
unit cell. The molecule shows C3 point group symmetry and hence
all three ligands are equivalent. The SbS6 chromophore of
[Sb(mchdtc)3] is of a distorted octahedral (dOh) geometry. The
asymmetric unit shows two SbAS bonds, 2.5251(4) and
2.9732(4) Å, indicating anisobidentate binding. The short thioure-
ide CAN distance, 1.3297(17) Å, is due to electron delocalization
over the S2CN moiety. The bite angle associated with the dithiocar-
bamate ligand is 64.71(3)°. In [Sb(chedtc)3] (2), the antimony cen-
ter is in a distorted octahedral coordination environment of six

602
S. Sivasekar et al. / Polyhedron 85 (2015) 598–606
3.6. Continuous shape measure
The continuous shape measure (CShM) quantifies the distance
of a given structure from the desired ideal symmetry or from a ref-
erence shape [36,38–40]. Descriptions of geometries, such as
‘slightly distorted’ or ‘severely distorted’, relative to the reference
polyhedron is a common practice. The degree of distortion of a par-
ticular molecular structure from an ideal polyhedron can be quan-
tified by symmetry measures. CShM methodology has been
successful in such quantification in dealing with transition metal
complexes and metal oxides. For ‘six coordination’ the ideal geom-
etries are ideal octahedron (iOh) or ideal trigonal prism (itp). In the
present investigation, the coordination around antimony has been
found to be distorted octahedron (dOh) in (1) and (2). In the case of
compound (3), it has been found to be distorted pentagonal pyra-
mid (dPpy). It is natural to consider the transformation of dPpy to
iOh or itp. In the present case, the CShM values of the SbS6 cores in
the three complexes are 8.995, 8.063 and 26.895 for (1), (2) and (3)
respectively. The observed CShM values follow the order
(3) > (1) > (2). Complex (3) deviates to the largest extent from the
octahedral geometry compared to (1) and (2) because of the largest
steric demand of the two cyclohexyl rings. The observed CShM val-
ues clearly indicate the closeness of (1) and (2) to an octahedral
geometry. The other SbS6 core associated with compound (3) is
not clearly octahedral. Distortion from the octahedral geometry
is minimal in the ethyl and methyl analogues and is a maximum
in the dicyclohexyl analogue due to steric demands, which is quan-
tified by the reported CShM values.
Fig. 1. ORTEP of [Sb(chmdtc)3] (1) S10, S20 = ꢀx + y, ꢀx, z; S100, S200 = ꢀy, x ꢀ y,
z (hydrogens are excluded).
3.7. BVS calculations
Bond valence sum (BVS) calculations offer a reliable method of
assigning formal oxidation states to an atom in a compound from
the bond parameters. The method depends on the Rij value for an
i–j bond in a compound which is predominantly ionic [41–43]. In
a compound, the oxidation state of a central atom ‘i’ bonded to ‘j’
corresponds to the bond valence, Sij, and the total valence of the
central atom, which is its oxidation state,
R
Sij = exp[(Ro ꢀ Rij)/b]
where Ro is used as reported [41] and Rij is the experimentally
determined bond distance. The constant b can be assumed to be
0.37 [44,45]. Bond valence sums calculated for the complexes from
the structural data reported in this study are 3.3957, 3.3528 and
3.4256 for (1), (2) and (3) respectively. The calculated values are
found to be higher than the expected formal oxidation state of
+3. The higher values observed in the present set of compounds
support the fact that the SbAS bonds are more covalent and the
back bonding effect is very highly pronounced in the compounds.
3.8. Characterization of Sb2S3
3.8.1. Powder XRD
A powder XRD of the solvothermally prepared antimony sulfide
is shown in Fig. 4. The broad pattern indicates nano sized particles
and it matches well with the JCPDS pattern reported for Sb2S3,
PDF# 42:1393. The pattern was indexed to an orthorhombic unit
cell with the following constants: a = 11.22, b = 11.28 and
c = 3.84 Å. Three important signals, namely (130), (310) and
(211), are observed as indicated in the Fig. 4 [46]. The ease of for-
mation of Sb2S3 (<20 nm) from the parent dithiocarbamate precur-
sors followed the order: (3) > (1) > (2).
Fig. 2. ORTEP of [Sb(chedtc)3] (2) (hydrogens are excluded).
2.867 Å and H(30A)ꢁ ꢁ ꢁC(30): 2.369 Å, are observed. The nature of
the substituents to a large extent is responsible for the structural
variations, in addition to the lone pair of electrons on the anti-
mony atom. The shift of the metal atom position relative to the
geometrical center of the ligating sulfur atoms (0.511; 0.421 and
0.612 Å in (1), (2) and (3) respectively) is due to the lone pair effect.
An analogous shift was observed in other transition metal com-
pounds [36]. In compound (1), supramolecular interactions are
absent whereas in compounds (2) and (3), they are observed,
which clearly indicates the influence of the substituents in the
crystal packing in these types of compounds [37].
3.8.2. FESEM and EDX
An SE micrograph of the prepared antimony sulfide is shown in
Fig. 5. The morphology of the surface shows oval shaped crystalline
grains with a large size distribution. The energy dispersive spec-
trum confirmed the presence of antimony and sulfur in a 2:3 ratio.

S. Sivasekar et al. / Polyhedron 85 (2015) 598–606
603
Fig. 3. ORTEP of [Sb(dchdtc)3] (3) (hydrogens and solvent of crystallization are excluded).
Fig. 4. Powder XRD of nano Sb2S3.
3.8.3. HRTEM and SAED
indicated by markers in the figure. The average distance
between the fringes is less than 1 nm. The two SAED patterns
confirm the crystalline nature of the sample along the fringe
planes.
HRTEM and SAED (2 insets) are shown in Fig. 6. HRTEM
shows the Sb2S3 to be nano fibers which are <20 nm size. The
crystal lattice fringes are clearly visible in the HRTEM pattern,

604
S. Sivasekar et al. / Polyhedron 85 (2015) 598–606
Fig. 5. FESEM and EDX of nano Sb2S3.
Fig. 6. HRTEM and SAED of nano Sb2S3.
3+
3.9. Characterization of the (Tl+2/3 ꢀ 2d)[Tl
pyrochlore
Sb3+y]Sb2O6O01/3 ꢀ d
1 ꢀ y
3.9.1. Powder XRD
The powder XRD of the (Tl+2/3ꢀ2d)[Tl13ꢀ+ ySb3+y]Sb2O6O01/3ꢀd (where
d ꢂ 0.05) pyrochlore prepared from an equimolar mixture of
[Sb(chmdtc)3] and [Tl(chmdtc)3] precursors is shown in Fig. 7. The
powder XRD pattern of the sample obtained by heating the reactants
at 295 °C showed no resemblance to the precursors or the reported
sulfides of antimony and thallium. The pattern also does not bear
any resemblance to the patterns reported for the corresponding
oxides. EDX analysis also showed non-specific ratios of elements
such as Tl, Sb, S and O, indicating the formation of an intermediate.
The PXRD pattern of the sample obtained at 350 °C matches the
pattern reported for the (Tl+2/3ꢀ2d)[Tl31ꢀ+ ySb3+y]Sb2O6O01/3ꢀd pyrochlore
[24]. The PXRD pattern of the sample obtained at 350 °C showed
signals at (311), (222), (400) and (440). The sample obtained at
750 °C showed an increase in the (311)/(222) intensity ratio, which
is a characteristic occurrence in this class of pyrochlores [24].
Fig. 7. Powder XRD patterns of precursor mixtures at three temperatures.
Sb3+y]Sb2O6O01/3ꢀd pyrochlore obtained at 750 °C is shown in
Fig. 9. The experimental ratio of Sb/Tl in the sample heated at
350 °C was found to be 1.88 and the ratio for the sample heated
at 750 °C was found to be 5.37. It has been observed that the
powder XRD patterns for all the allowed variations of ‘d’, will be
similar. The sample obtained at 350 °C corresponds to (Tl0+.57
)
[Tl30.+22Sb30.+44]Sb2O6O00.29, with a Sb/Tl ratio of 1.90, matching the
EDX value. Thallium within () brackets refers to its presence in
the +1 oxidation state and within [ ] brackets refers to Tl and Sb
being in the +3 state, conventionally. The decreased thallium
content of the pyrochlore obtained at 750 °C indicates the volatili-
zation of thallium, leading to enhanced defects and still retaining
the pyrochlore phase. The pyrochlore appears as nano crystals
(<100 nm), as observed in the FESEM micrograph.
3.9.2. FESEM and EDX
EDX of the two samples obtained at two different tempera-
3+
tures are shown in Fig. 8. The SE micrograph of (Tl+2/3ꢀ2d)[Tl
1ꢀy

S. Sivasekar et al. / Polyhedron 85 (2015) 598–606
605
Fig. 8. EDX of TlASbAO pyrochlore at 350 and750 °C.
polyhedron was found to be a distorted pentagonal pyramid (dPpy)
and the geometry is forced on it by the steric influence of the cyclo-
hexyl substituents in addition to the rigid bite angle of the dithio-
carbamate ligands. CShM calculations on the chromophores clearly
quantify the extent of deviation from the ideal octahedral geome-
try. Compounds (1) and (2) showed relatively small deviations
from an octahedral geometry compared to the SbS6 core associated
with compound (3), in line with the CShM values. The higher bond
valence sums (BVS) observed in the present set of compounds
support the fact that the SbAS bonds are more covalent and the
back bonding effect is very highly pronounced. The three dithiocar-
bamates yielded nano Sb2S3 (<20 nm) in a non-conventional solvo-
thermal process. The ease of formation of the nanosulfide followed
the order: (3) > (1) > (2). The nano wires of Sb2S3 have been charac-
3+
terized by FESEM, EDX, HRTEM and SAED. (Tl+2/3ꢀ2d)[Tl Sb3+
]
1ꢀy
y
Sb2O6O01/3ꢀd (where d ꢂ 0.05) pyrochlore has been prepared from
an equimolar mixture of [Sb(chmdtc)3] and [Tl(chmdtc)3] as precur-
sors. The pyrochlore, (Tl+0.57)[Tl30.+22Sb03.+44]Sb2O6O00.29 was found to
consist of cuboids with sizes less than 100 nm and it was character-
ized by PXRD, EDX and FESEM techniques.
3+
Fig. 9. FESEM micrograph of (Tl+2/3ꢀ2d)[Tl
Sb3y+]Sb2O6O01/3ꢀd
.
1 ꢀ y
Appendix A. Supplementary data
4. Conclusions
CCDC 954049, 954050 and 954051 contains the supplementary
crystallographic data for (1), (2) and (3), 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. Supplementary
data associated with this article can be found, in the online version,
at http://dx.doi.org/10.1016/j.poly.2014.09.028.
The compounds [Sb(chmdtc)3] (1), [Sb(chedtc)3] (2) and
[Sb(dchdtc)3] (3) reported in this study showed only charge
transfer transitions, apart from intraligand transitions, in their
electronic spectra. The IR spectra of the compounds showed the
contribution of thioureide bonds to the structures. The 1H and
13C NMR spectra of the complexes clearly indicated that the imme-
diate environment around the thioureide nitrogen was largely
affected by complex formation. TG analysis confirmed the stoichi-
ometry of the compounds perfectly and the formation of Sb2S3 as
the final residue was unequivocally proven. Single crystal X-ray
structures of the compounds showed the SbAS bonds to be clearly
anisobidentate in nature. The thioureide bond distances were
between 1.327 and 1.331 Å, clearly indicating the resonant flow
of electron density from the nitrogen atom to the metal. The bite
angles of the dithiocarbamate ligands, observed in the range
64.16–66.46° in the complexes, organize the geometry around
the antimony center. Short contacts involving Sꢁ ꢁ ꢁH interactions
are absent in [Sb(chmdtc)3] (1), in contrast to those observed in
the other two compounds in spite of the fact that its density
(g/cm3) was relatively maximal (1.475 for (1), 1.387 for (2),
1.289 for (3)). In [Sb(chmdtc)3] (1) and [Sb(chedtc)3] (2), the
coordination geometries around antimony were found to be
distorted octahedral (dOh). In [Sb(dchdtc)3] (3), the coordination
References
[1] M. Veith, J. Chem. Soc., Dalton Trans. (2002) 2405.
[2] R. García-Rodríguez, M.P. Hendricks, B.M. Cossairt, H. Liu, J.S. Owen, Chem.
Mater. 25 (2013) 1233.
[3] K. Ramasamy, M.A. Malik, P. O’Brien, J. Raftery, M. Helliwell, Chem. Mater. 22
(2010) 6328–6340.
[4] M.D. Regulacio, N. Tomson, S.L. Stoll, Chem. Mater. 17 (2005) 3114.
[5] M. Becht, T. Gerfin, K.H. Dahmen, Chem. Mater. 5 (1993) 137.
[6] C. Xu, T.H. Baum, A.L. Rheingold, Chem. Mater. 10 (1998) 2329.
[7] D.C. Bradley, Chem. Rev. 89 (1989) 1317.
[8] A. Gringeri, P.C. Keng, R.F. Borch, Cancer Res. 48 (1988) 5708.
[9] M.H. Zeng, H. Liang, R.X. Hu, Chin. J. Appl. Chem. 8 (2001) 837.
[10] T.L. Sheng, X.T. Wu, P. Lin, Polyhedron 18 (1999) 1049.
[11] L.J. Farrugia, F.J. Lawlor, N.C. Norman, J. Chem. Soc., Dalton Trans. (1995) 1163.
[12] D. Coucouvanis, Prog. Inorg. Chem. 11 (1970) 233.
[13] I.I. Ozturk, C.N. Banti, N. Kourkoumelis, M.J. Manos, A.J. Tasiopoulos, A.M.
Owczarzak, M. Kubicki, S.K. Hadjikakou, Polyhedron 67 (2014) 89.
[14] J. Rodriguez- Castro, P. Dale, M.F. Mahon, K.C. Molloy, L.M. Peter, Chem. Mater.
19 (2007) 3219–3226.

606
S. Sivasekar et al. / Polyhedron 85 (2015) 598–606
[15] M.D. Regulacio, M.H. Pablico, J.A. Vasquez, P.N. Myers, S. Gentry, M. Prushan, S-
W. Tam-Chang, S.L. Stoll, Inorg. Chem. 47 (2008) 1512.
[31] B. Arul Prakasam, K. Ramalingam, G. Bocelli, A. Cantoni, Phosphorus Sulfur
Silicon 184 (2009) 2020.
[16] J.D.E.T. Wilton-Ely, D. Solanki, E.R. Knight, K.B. Holt, A.L. Thompson, G. Hogarth,
Inorg. Chem. 47 (2008) 9642.
[32] R. Baskaran, K. Ramalingam, G. Bocelli, A. Cantoni, C. Rizzloi, J. Coord. Chem. 61
(2008) 1710.
[17] N. Salvarese, N. Morellato, A. Venzo, F. Refosco, A. Dolmella, C. Bolzati, Inorg.
Chem. 52 (2013) 6365.
[33] M.V. Rajasekaran, G.V.R. Chandramouli, P.T. Manoharan, Chem. Phys. Lett. 162
(1989) 110.
[18] S.S. Garje, V.K. Jain, Coord. Chem. Rev. 236 (2003) 35.
[19] P.J. Heard, Prog. Inorg. Chem. 53 (2005) 1.
[20] X. Wang, K.F. Cai, F. Shang, S. Chen, J. Nanopart. Res. 15 (2013) 1541.
[21] O. Savadogo, K.C. Mandal, Sol. Energy Mater. Sol. Cells 26 (1992) 117.
[22] L. Zhang, L. Chen, H.Q. Wan, H.D. Zhou, J.M. Chen, Cryst. Res. Technol. 45 (2010)
178.
[34] Available at: <http://sdbs.riodb.aist.go.jp/sdbs/cgi-bin/cre_index.cgi>.
[35] H.L.M. Van Gaal, J.W. Diesveld, F.W. Pijpers, J.G.M. Van Der Lindan, Inorg.
Chem. 18 (1979) 3246.
[36] K.M. Ok, P.S. Halasyamani, D. Casanova, M. Llunell, S. Alvarez, Chem. Mater. 18
(2006) 3176.
[37] Y. Liu, E.R.T. Tiekink, CrystEngComm 7 (2005) 20.
[38] S. Alvarez, D. Avnir, M. Llunell, M. Pinsky, New J. Chem. 26 (2002) 996.
[39] H. Zabrodsky, S. Peleg, D. Avnir, J. Am. Chem. Soc. 114 (1992) 7843.
[40] S. Keinan, D. Avnir, J. Am. Chem. Soc. 122 (2000) 4378.
[41] N.E. Bresse, M. O0Keefe, Acta Crystallogr., Sect. B 47 (1991) 192.
[42] S.P. Summers, K.A. Abboud, S.R. Farrah, G.J. Palenik, Inorg. Chem. 33 (1994) 88.
[43] I.D. Brown, D. Altermatt, Acta Crystallogr., Sect. B 41 (1985) 244.
[44] I.D. Brown, The Chemical Bond in Inorganic Chemistry, Oxford University
Press, Oxford, UK, 2002.
[23] M.A. Subramanian, B.H. Tody, A.P. Ramirez, W.J. Harshall, A.W. Sleight, G.H.
Kwei, Science 273 (1996) 81.
[24] Y.-S. Hong, K. Kim, J. Mater. Chem. 11 (2001) 1533.
[25] Bruker AXS Inc., 6300 Enterprise Lane, Madison, WI 53719–1173, USA.
[26] N. Walker, D. Stuart, Acta Crystallogr., Sect. A 39 (1983) 158.
[27] P. Gluzinski, Set of Programs for X-ray Structural Calculation, Icho Polish
Academy of Sciences, Warsaw, Poland, 1987.
[28] G.M. Sheldrick, SHELX 97, Program for Crystal Structure Analysis, University of
Gottingen, Germany, 1997.
[45] I.D. Brown, Chem. Rev. 109 (2009) 6858.
[29] L.J. Farrugia, ORTEP-3 for Windows, University of Glasgow, Scotland, UK, 1999.
[30] G.S. Sivagurunathan, K. Ramalingam, C. Rizzoli, Polyhedron 65 (2013) 316.
[46] A. Alemi, S. Woo Joo, Y. Hanifehpour, A. Khandar, A. Morsali, Bong-KiMin, J.
Nanomater. 1 (2011) 1–5, http://dx.doi.org/10.1155/2011/186528.