Continuous Shape Measure of electronic effect free steric distortions in tris(dithiocarbamato)indium(III): Synthesis, spectral, electrochemical, single crystal X-ray structural investigations and BVS calculations on tris(dithiocarbamato)indium(III) comple

Article abstract of DOI:10.1016/j.poly.2014.01.032

Geometrical distortions from an ideal octahedral geometry (iOh) towards an ideal trigonal prism (itp) in tris(dithiocarbamato)indium(III) complexes have been quantified by Continuous Shape Measure (CShM) analysis. Three tris(disubstituted dithiocarbamato)

Full text of DOI:10.1016/j.poly.2014.01.032

Polyhedron 72 (2014) 96–102
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Continuous Shape Measure of electronic effect free steric distortions
in tris(dithiocarbamato)indium(III): Synthesis, spectral, electrochemical,
single crystal X-ray structural investigations and BVS calculations
on tris(dithiocarbamato)indium(III) complexes
b
Gurunathan Senthilkumar Sivagurunathan a, Kuppukkannu Ramalingam a, , Corrado Rizzoli
⇑
a Department of Chemistry, Annamalai University, Annamalainagar 608 002, Tamil Nadu, 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:
Geometrical distortions from an ideal octahedral geometry (iOh) towards an ideal trigonal prism (itp) in
tris(dithiocarbamato)indium(III) complexes have been quantified by Continuous Shape Measure (CShM)
analysis. Three tris(disubstituted dithiocarbamato)indium(III) complexes, cyclohexylmethyldithiocarbamate
(chmdtc) (1), cyclohexylethyldithiocarbamate (chedtc) (2) and dicyclohexyldithiocarbamate (dchdtc) (3),
have been prepared and characterized by spectral, cyclic voltammetric and single crystal X-ray structural
techniques. The electronic effects are at a minimum for trivalent indium and the distortions follow the
order: (3) > (1) > (2), as per the CShM values. The IR spectra indicate a contribution of the thioureide form
of the dithiocarbamates to the stabilization of the compounds, with a characteristic C–N stretch in
Received 15 October 2013
Accepted 25 January 2014
Available online 11 February 2014
Keywords:
Continuous Shape Measure
Dithiocarbamate
Indium
Cyclic voltammetry
X-ray crystal structures
the range 1446–1475 cmꢀ1 1H NMR spectra indicate that the protons in the vicinity of the thioureide
.
nitrogen are the most affected on complexation. 13C NMR spectra showed the characteristic thioureide
carbon signals at 201.18, 200.98 and 200.94 ppm for complexes (1), (2) and (3) respectively. Cyclic
voltammetric investigations revealed three single electron additions to the trivalent indium. The single
crystal X-ray structures showed little change in the In–S and thioureide C–N bond distances or the
S–In–S bite angles with changes in the steric demands, in the absence of any significant electronic effects.
Bond Valence Sums (BVS) of the complexes identified the formal oxidation of indium to be +3 and the
observed deviations show the increased covalent bonding. Nano indium sulfides have been prepared
from the dithiocarbamates through a non-conventional solvothermal process. The nanosulfides have
been characterized by SEM and EDX techniques. The ease and yield of formation follow the order:
(3) > (1) > (2).
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
blue-green emitting phosphor [23–25]. Indium dithiocarbamates
have been used as single source precursors for indium sulfide thin
Interest in group 13 elements and their compounds has been
remarkable in the past decade [1–5]. Among the group elements,
indium(III) is a functional group-tolerant Lewis acid in organic
transformations [6–9]. 111In and 113In find extensive use in diagnos-
tic imaging in medicine [10–12]. Indium is used as a catalyst for
polymerization of caprolactone and lactides [13–16]. The sulfide is
highly stable and shows valuable optical, acoustical and electronic
properties [17–21]. The b-In2S3 thin film is an important material
for optoelectronic and photo voltaic applications [22]. In2S3 is a
films and nano particles [26–28]. The number of reports on
tris(dithicarbamato)indium(III) complexes is sparse. This paper
reports the synthesis and structures of three indium(III) complexes
with bidentate disubstituted dithiocarbamates, chmdtc, chedtc
and dchdtc (where chmdtc = cyclohexylmethyldithiocarbamate,
chedtc = cyclohexylethyldithiocarbamate and dchdtc = dicyclohexyl
dithiocarbamate). The complexes have been analyzed by IR, NMR
spectral and cyclic voltammetric techniques. The single crystal
X-ray structural data has been used for the calculation of BVS. The
indium(III) complexes provide an outer sphere electron free envi-
ronment for the calculation of Continuous Shape Measurements
(CShM) and hence provide a measure of the steric destabilization
for the analyzed compounds in this
⇑
Corresponding author. Tel.: +91 413 2202834; fax: +91 414 42265.
E-mail address: krauchem@yahoo.com (K. Ramalingam).
http://dx.doi.org/10.1016/j.poly.2014.01.032
0277-5387/Ó 2014 Elsevier Ltd. All rights reserved.

G.S. Sivagurunathan et al. / Polyhedron 72 (2014) 96–102
97
C29H56InN3O2S6: C, 44.32; H, 7.18; N, 5.35. Found: C, 44.28; H,
7.15; N, 5.33%.
-
CS2
-
N
dchdtc
CS2
-
2.2.3. Synthesis of tris(dicyclohexyldithiocarbamato)indium(III);
[In(dchdtc)3]ꢁ2CH3OH (3)
N
CS2
chedtc
N
chmdtc
Dicyclohexylamine (30 mmol, 1.8 mL in 25 mL of methanol),
carbon disulfide (30 mmol, 0.75 mL) and InCl3 (10 mmol, 2.2 g)
were used and the procedure as described above was followed.
Anal. Calc. for C41H74InN3O2S6: C, 51.93; H, 7.87; N, 4.43. Found:
C, 51.88; H, 7.84; N, 4.40%.
investigation [29–31]. The indium(III) complexes have been used as
precursors for the preparation of b-In2S3 by a non-conventional
solvothermal method and the ease of nanosulfide formation is cor-
related to the structure of the dithiocarbamate. Powder XRD and
SEM-EDS analysis have been used to characterize the nanosulfide.
2.2.4. Preparation of b-In2S3 by non-conventional solvothermal
decomposition of tris(disubstituteddithiocarbamato)indium(III)
1 mM of the tris(disubstituted dithiocarbamato)indium(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. The solid yellow indium sulfide obtained was separated
from chloroform, washed with ether and chloroform, and then
dried in air.
2. Experimental
All the reagents and solvents employed were commercially
available analytical grade materials and were used as supplied
without further purification. IR spectra on an ABB Bomem MB
104 spectrometer (range 4000–400 cmꢀ1) were recorded as KBr
pellets. Scanning electron micrographs of the samples were re-
corded with JOEL JSM-5610Lv microscopes. Cyclic voltammetric
studies were carried out using a CH1604C electrochemical ana-
lyzer. NMR spectra were recorded on a Bruker 400 MHz spectrom-
eter at room temperature using CDCl3 as the solvent. The powder
diffraction data were collected in the 2h range 2–80° using a Bru-
3. Results and discussion
3.1. Infrared spectra
Table 1 lists important spectral and cyclicvoltammetric data. In
the IR spectra of the compounds, characteristic thioureide stretch-
ing bands are observed at 1475 cmꢀ1 for [In(chmdtc)3] (1),
1473 cmꢀ1 for [In(chedtc)3] (2) and 1446 cmꢀ1 for [In(dchdtc)3]
(3). The stretching band of (3) is significantly lower than those ob-
served for (1) and (2) due to the steric effect of two bulky cyclo-
hexyl substituents, preventing the delocalization of the lone pair
of electrons on the nitrogen between the (R2)N–C(S2) bond. The
mc–s bands appear at 1007, 1001 and 1019 cmꢀ1 for (1), (2) and
(3) respectively, without any splitting, supporting the isobidentate
coordination of the dithiocarbamates to the metal centre. In com-
ker-D8 X-ray diffractometer equipped with Cu K
a radiation at
fixed current and potential. The scan speed and step sizes were
0.05° minꢀ1 and 0.00657, respectively.
2.1. X-ray crystallography
Intensity data were collected at ambient temperature (295 K)
on a Bruker APEXII CCD diffractometer with graphite monochro-
mated Mo K
a radiation (k = 0.71073 Å) and were corrected for
absorption with a multi-scan technique [32–34]. The structures
were solved by direct methods using SIR92 and were refined by
SHELXL97 [35,36]. The non-hydrogen atoms were refined anisotrop-
ically and all the hydrogen atoms were fixed geometrically. Molec-
ular plots were obtained using the ORTEP-3 program [37].
pounds (1), (2) and (3),
mC–H vibrations appear in the region 2852–
2931 cmꢀ1
.
3.2. Cyclic voltammetry
Electrochemical studies on the indium compounds have shown
them to be poor electroactive materials in aqueous medium be-
cause of the preventive water sheath around the ions [38,39]. In-
dium phthalocyanine gives only ring based electrochemical
responses [40]. Even in non-aqueous media, the voltammetric re-
sponses of trivalent gallium and indium(III) have been poor
[41,42]. Early polarographic studies on indium(III) dithiolates indi-
cated a three step electron reduction [43]. A voltammetric study on
bismuth indium telluride in citrate buffer indicated a clear single
step three electron reduction with HMDE [44]. Electrochemical
reduction of InCl3 solution in LiCl–KCl eutectic at 450 °C by voltam-
metry and chronopotentiometry revealed that the reduction of tri-
valent indium to indium metal is a two step mechanism with the
formation of a stable In2+ intermediate and then the indium metal
[45–47]. A differential pulse polarographic determination of trace
level indium(III) as its morpholine dithiocarbamate concentrate
showed a conspicuous signal at ꢂ600 mV [48]. A recent review
indicated that the number of steps involved in the reduction de-
pends on the current density [49]. Fig. 1a and b show representa-
tive cyclic voltammograms recorded for complex (3) with glassy
carbon and platinum working electrodes, respectively. In Fig. 1a,
three reduction peaks are observed at ꢀ400, ꢀ1100 and
ꢀ1600 mV, corresponding to three one electron reductions. On
the anodic side, signals are observed at ꢀ800, ꢀ200, +1100 and
+1600 mVs. The ꢀ400/ꢀ200 mV redox couple is quasi-reversible
2.2. Synthesis of the complexes and the non-conventional solvothermal
preparation of indium(III) sulfide
2.2.1. Synthesis of tris(cyclohexylmethyldithiocarbamato)indium(III);
[In(chmdtc)3]ꢁC6H12 (1)
Cyclohexylmethyl amine (30 mmol, 1.2 mL) in methanol
(25 mL) and carbon disulfide (30 mmol, 0.75 mL) in methanol were
mixed under ice cold conditions (0–5 °C) to obtain a yellow dith-
iocarbamic acid solution. To the freshly prepared dithiocarbamic
acid solution, a methanolic solution (3:1 methanol:water) of InCl3
(10 mmol, 2.2 g) was added dropwise with constant stirring for
about 2 h. The white precipitate that separated from the mixture
was filtered, washed with methanol and dried in air. The solid
was then recrystallized from a dichloromethane toluene (1:1) mix-
ture. The product was recrystallized from cyclohexane. Anal. Calc.
for C30H54InN3S6: C, 47.16; H, 7.12; N, 5.50. Found: C, 47.11; H,
7.08; N, 5.45%.
2.2.2. Synthesis of tris(cyclohexylethyldithiocarbamato)indium(III);
[In(chedtc)3]ꢁ2CH3OH (2)
Cyclohexylethylamine (30 mmol, 1.3 mL in 25 mL of methanol),
carbon disulfide (30 mmol, 0.75 mL) and InCl3 (10 mmol, 2.2 g)
were used and the procedure described in 2.2.1 was followed.
The product was recrystallized from toluene. Anal. Calc. for

98
G.S. Sivagurunathan et al. / Polyhedron 72 (2014) 96–102
Table 1
IR spectral (cmꢀ1) and cyclic voltammetric (mV) data.
Compound
IR (cmꢀ1
)
CV (mV)
mC–N
mC–S
mC–H
Reduction
Oxidation
[In(chmdtc)3] (1)
[In(chedtc)3] (2)
[In(dchdtc)3] (3)
1475
1473
1446
1007
1001
1019
2852
2853
2931
ꢀ470,ꢀ1300, ꢀ1650
ꢀ460,ꢀ1250, ꢀ1550
ꢀ400, ꢀ1100, ꢀ1600
ꢀ850, ꢀ260, +1150 and +1650
ꢀ800, ꢀ250, +1050 and +1550
ꢀ800, ꢀ200, +1100 and +1600
Fig. 1. (a) Cyclic voltammogram with a glassy carbon electrode. (b) Cyclic voltammogram with a platinum electrode. (c) Anodic scan of the dithiocarbamate ligand.
Table 2
NMR spectral data (ppm).
in nature. The other two redox processes are irreversible in nature.
The signal on the anodic side at +1600 mV is due to the oxidation of
the dithiocarbamate ligand to the disulfide. Fig. 1b shows three
clearly irreversible reductions at ꢀ550, ꢀ1150 and ꢀ1500 mV, cor-
responding to three one electron reductions. All the three reduc-
tions are completely irreversible in nature. A signal at +300 mV is
due to the reduction of the electro oxidized disulfide, which ap-
pears as a weak signal around +1600 mV in the figure. Fig. 1c
shows the anodic scan of the dithiocarbamate ligand produced
in situ. The currents at +1700 and +500 mV are due to the oxidation
of the dithiocarbamate to the disulfide and its subsequent reduc-
tion respectively. This is the first report in which three one electron
reduction processes are recorded for In3+ reduction with glassy car-
bon and platinum electrodes. However, the redox processes with
platinum electrodes are completely irreversible in nature.
Complex
NMR
1H
a
-CH
b-CH2/
d-CH2
c
-CH2
&
a’-CH3/CH2/CH
N13CS2
(1)
4.71(m)
1.81, 1.82(e)
1.65–1.68
3.26(s)
–
13C
1H
65.26
4.72(m)
25.33–30.18
1.82–2.00(e)
1.57–1.65
36.60
201.18
–
(2)
(3)
3.79(q)
1.30–1.38(t)
44.90
13.99
–
13C
1H
65.84
30.69
200.98
–
21.51–25.63
1.25–1.28(a)
1.41–1.79
4.83(m)
(Collapsed)
25.07–29.76
13C
69.54
–
200.94
(
a0-CH3) attached to the nitrogen appear at 3.26(s) ppm
(2.421 ppm), with a proton integration corresponding to three.
The
-CH and a0-CH3 protons are affected to a maximum extent
3.3. NMR spectra
a
NMR spectral data of the indium complexes are listed in Table 2.
The chemical shifts reported in the Spectral Data Base for Organic
compounds (SDBS) for the parent amines are shown in brackets
[50]. The 1H NMR spectrum of complex (1) shows an intense signal
at 4.71(m) ppm (2.303 ppm), corresponding to single proton
on complexation. In the cyclohexyl ring, all the equatorial protons
are deshielded to a large extent compared to the axial protons. The
equatorial protons attached to b- and
c-carbon atoms appear at
1.81 and 1.82 ppm [J = 5.6 Hz]. The d-equatorial proton appears
at 1.65–1.68 ppm [J = 12 Hz]. The 13C NMR spectrum of (1) shows
a weak signal at 201.18 ppm due to the thioureide carbon [51].
integration due to
a-CH of the cyclohexyl ring. The CH3 protons

G.S. Sivagurunathan et al. / Polyhedron 72 (2014) 96–102
99
The
(58.63 ppm) and a0-CH3 appears at 36.60 ppm (33.60 ppm). The
b, - and d-carbon signals are the least affected and appear at
25.33, 25.43 and 30.18 ppm respectively. In complex (2), the 1H
NMR spectrum shows the -CH proton of the cyclohexyl ring at
a
-carbon of the cyclohexyl ring appears at 65.26 ppm
complex has a crystallographically imposed three-fold symmetry,
three cyclohexylmethyldithiocarbamate ligands being coordinated
to indium in a distorted octahedral geometry. The indium–sulfur
bond distances in the asymmetric unit are 2.5909(10) and
2.5977(9) Å. The thioureide bond distance in the compound is
1.330(4) Å, indicating its partial double bond nature. The C–S bond
distances are identical. The distortion from a regular octahedral
geometry is due to the small bite angle of the dithiocarbamate li-
gand (S(1)–In(1)–S(2): 69.49(3)°). The unit cell contains cyclohex-
ane solvent molecules disordered over two sets of orientations
about a three-fold inversion axis, with a complex/solvent molar ra-
tio of 2:1.
c
a
4.72(m) ppm and a0-CH2 appears at 3.79(q) ppm, corresponding
to two protons. The b0-CH3 protons of the ethyl group appear as
a well resolved triplet at 1.30–1.38(t) [J = 32 Hz] ppm. The 13C
NMR spectrum of (2) shows the characteristic thioureide signal
at 200.98 ppm. b0-CH3 appears at 13.99 ppm, as a much shielded
signal, and a0-CH2 appears to be highly deshielded at 44.90 ppm.
In the case of complex (3), the
a-CH proton of the cyclohexyl ring
is observed at 4.83(m) ppm (2.546 ppm). The b,
c
- and d-CH2 sig-
Complex (2) crystallizes in the monoclinic space group P21/n,
with four formula units per unit cell. An ORTEP plot of the molecule
is shown in Fig. 3. The In–S bond distances show a relatively wide
range of distances, from 2.5775(13) to 2.6084(12) Å, the observed
asymmetry being possibly due to the presence of sterically
demanding ethyl groups. The C–S bond distances vary from
1.718(4) to 1.737(4) Å (mean value 1.728(2) Å), indicating electron
nals appear in the region 1.41–1.79 ppm (collapsed) (1.606–
1.856 ppm). The axial proton signals are observed between 1.25
and 1.28 ppm (1.021–1.246 ppm). The 13C NMR spectrum exhibits
a weak characteristic signal due to the thioureide carbon at
200.94 ppm. The 13C NMR signal corresponding to the
a-C(H) car-
bon of the cyclohexyl ring is found to be significantly shielded and
appears at 69.54 ppm (53.17 ppm). The b-C(H2), and d-C(H2) car-
bons appear in the region 25.07–29.76 ppm (26.32–34.51 ppm).
Signals observed at ꢂ7.20 and 2.35 ppm in the 1H NMR spectra
of the three compounds are due to the aromatic and methyl pro-
tons of toluene, which is the solvent used for crystallization. The
NMR spectra of the complexes clearly indicate that the immediate
environment around the thioureide nitrogen is largely affected by
complex formation.
ꢀ
delocalization within the NCS2 fragments. One of the three thio-
ureide distances (C(19)–N(3) = 1.318(6) Å) is significantly shorter
than other two (1.331(5) Å) due to the packing requirements
and, in general, the thioureide bonds have partial double bond nat-
ure. The observed dithiocarbamate bite angles are 69.53(4)°,
69.59(4)° and 69.68(4)°. Because of the small bite angles, the InS6
unit displays a distorted octahedral geometry. The unit cell con-
tains toluene solvent molecules disordered over two sets of orien-
tations about an inversion centre, with a complex/solvent molar
ratio of 2:1.
3.4. Single crystal X-ray structural analysis
An ORTEP plot of the molecule (3) is shown in Fig. 4. In compound
(3), the In–S bond distances are observed in the range 2.562(12)–
2.6332(10) Å, clearly exhibiting the rather large asymmetry associ-
ated with them. Thisꢀasymmetry is reflected in the C–S bonds of
Details of the data collection and refinement parameters for
complexes (1), (2) and (3) are given in Table 3. Selected bond dis-
tances and angles are given in Table 4. An ORTEP plot of (1) is shown
in Fig. 2. Six complex molecules are present in the unit cell. The
each ((C6H11)2N)CS2
unit. The S(5)–In(1)–S(6) bite angle
Table 3
Crystal data, data collection and refinement parameters.
Complex
(1)
(2)
(3)
Empirical formula
Formula weight
Crystal dimensions
(mm)
2(C24H42InN3S6)ꢁC6H12
1443.85
0.10 ꢃ 0.08 ꢃ 0.05
2(C27H48InN3S6)ꢁC7H8
1535.98
0.32 ꢃ 0.24 ꢃ 0.18
2(C39H66InN3S6)ꢁC7H8
1860.51
0.21 ꢃ 0.18 ꢃ 0.11
Crystal system
Colour
Space group
hexagonal
colourless
R1
monoclinic
colourless
P21/n
monoclinic
colourless
C2/c
ꢀ
a (Å)
b (Å)
c (Å)
15.2648(3)
15.2648(3)
24.9980(11)
90
9.8581(19)
21.151(4)
18.446(4)
90
29.120(8)
15.402(4)
24.215(7)
90.00
a
(°)
b (°)
90
120
5044.5(3)
3
1.420
96.870(3)
90
3818.5(13)
2
1.336
0.970
113.034(4)
90.00
9995(5)
4
1.236
0.753
c
(°)
U (Å3)
Z
Dcalc (g cmꢀ3
)
l
(cmꢀ1
)
1.097
F(000)
2256
1604
3928
h Range (°)
2.2–25.2
1.5–25.2
1.5–25.2
Scan type
x
scans
x
scans
x scans
Index ranges
ꢀ18 6 h 6 13; ꢀ18 6 k 6 18; ꢀ30 6 l 6 26
ꢀ11 6 h 6 11; ꢀ25 6 k 6 25;ꢀ22 6 l 6 22
ꢀ34 6 h 6 34; ꢀ18 6 k 6 18; ꢀ29 6 l 6 29
Reflections collected
Unique reflections
Observed reflections
10293
2042
39877
6897
5143
53631
9043
1664
6980
Fo > 4r (Fo)
Weighting scheme
w = 1/[r r r
2(Fo2) + (0.0439P)2 + 8.7844P], where w = 1/[ 2(Fo2) + (0.0600P)2 + 3.2284P], where w = 1/[ 2(Fo2) + (0.0449P)2 + 6.0635P], where
P = (Fo2 + 2Fc2)/3
P = (Fo2 + 2Fc2)/3
436
P = (Fo2 + 2Fc2)/3
512
Parameters refined
135
Final R (observed data) 0.313
Final wR2 (unique data) 0.0921
0.0451
0.1266
0.0328
0.0897
Goodness of fit (GOF)
1.085
1.053
1.043
on F2

100
G.S. Sivagurunathan et al. / Polyhedron 72 (2014) 96–102
Table 4
Selected bond distances (Å) and angles (°).
(1)
(2)
(3)
In(1)–S(1) 2.5909(10)
In(1)–S(2) 2.5977(9)
In(1)–S(1) 2.5873(13)
In(1)–S(2) 2.5912(11)
In(1)–S(3) 2.5775(13)
In(1)–S(4) 2.6084(12)
In(1)–S(5) 2.6009(12)
In(1)–S(6) 2.5832(13)
C(1)–S(1) 1.724(4)
In(1)–S(1) 2.5903(9)
In(1)–S(2) 2.5819(10)
In(1)–S(3) 2.6008(9)
In(1)–S(4) 2.5627(11)
In(1)–S(5) 2.6332(10)
In(1)–S(6) 2.5724(10)
C(1)–S(1) 1.727(3)
C(1)–S(2) 1.731(3)
C(14)–S(3) 1.725(3)
C(14)–S(4) 1.725(3)
C(27)–S(5) 1.731(3)
C(27)–S(6) 1.720(3)
C(1)–N(1) 1.332(3)
C(14)–N(2) 1.330(3)
C(27)–N(3) 1.336(3)
C(1)–S(1) 1.723(3)
C(1)–S(2) 1.723(3)
C(1)–S(2) 1.729(4)
C(10)–S(3) 1.736(4)
C(10)–S(4) 1.719(5)
C(19)–S(5) 1.729(4)
C(19)–S(6) 1.729(4)
C(1)–N(1) 1.331(5)
C(10)–N(2) 1.330(6)
C(19)–N(3) 1.319(5)
C(1)–N(1) 1.330(4)
S(1)–In(1)–S(2)
69.49(3)
S(1)–In(1)–S(2)
69.69(3)
S(3)–In(1)–S(4)
69.59(4)
S(5)–In(1)–S(6)
69.53(4)
S(1)–In(1)–S(2) 69.13(2)
S(3)–In(1)–S(4) 69.16(2)
S(5)–In(1)–S(6) 68.84(2)
Fig. 3. ORTEP plot of In[(chedtc)3] (2) with displacement ellipsoids drawn at the 30%
probability level. Only the major components of the disordered cyclohexyl and
ethyl groups are shown. Hydrogen atoms and the solvent of crystallization are
omitted.
S(1)–C(1)–S(2)
118.2(2)
S(1)–C(1)–S(2)
117.9(2)
S(1)–C(1)–S(2)
116.16(14)
S(3)–C(10)–S(4)
117.9(2)
S(3)–C(14)–S(4)
116.30(16)
S(5)–C(19)–S(6)
117.5(3)
S(5)–C(27)–S(6)
117.02(15)
Fig. 4. ORTEP plot of In[(dchdtc)3] (3) with displacement ellipsoids drawn at the 30%
probability level. Only the major component of the disordered cyclohexyl ring is
shown. Hydrogen atoms and the solvent of crystallization are omitted.
shows a large spread of asymmetry of the metal sulfur bonds as
a result of the steric influence of the two cyclohexyl rings. In addi-
tion, complex (3) shows a relatively low bite angle due to the steric
repulsions.
Fig. 2. ORTEP plot of In[(chmdtc)3] (1), with anisotropic displacement ellipsoids
drawn at the 30% probability level. Only the major components of the disordered
cyclohexyl rings are shown. Hydrogen atoms and the solvent of crystallization are
omitted. Symmetry codes: (i) 1 ꢀ y,x ꢀ y,z; (ii) 1 ꢀ x + y,1 ꢀ x,z.
3.5. Continuous Shape Measure
(68.84(2)°) is significantly narrower than the other two angles
(69.16(3)° and 69.14(3)°) as a consequence of the steric demands
of the two bulky cyclohexyl rings. The thioureide bond distances
are not significantly different (mean value 1.3331(17) Å) and are
in agreement with the partial double bond nature of the interac-
tion. As observed in (2), the complex crystallizes with toluene sol-
vent molecules disordered over two sets of orientations about an
inversion centre, with a complex/solvent molar ratio of 2:1.
In all three compounds, the cyclohexyl rings assume chair con-
formations. On comparison of the three structures, a significant
observation that can be made is that the dicyclohexyl analogue
Continuous Shape Measure (CShM) effectively quantifies the
distance of a given structure from the desired ideal symmetry or
from a reference shape [52–55]. In practice, idealizations of molec-
ular structures is achieved by associating the positions of a set of
atoms with the vertices of a reference polyhedron and qualitative
descriptions such as ‘slightly distorted’ or ‘severely distorted’ rela-
tive to the reference polyhedron. To quantify the degree of distor-
tion of a particular molecular structure from an ideal polyhedron,
one can use symmetry measures. The CShM methodology has been
successfully applied to transition metal complexes and metal oxi-
des. In the present investigation, the Bailar twist angles for the

G.S. Sivagurunathan et al. / Polyhedron 72 (2014) 96–102
101
octahedral geometry than the methyl analogue (1). All three com-
plexes show very little tendency to distort towards an ideal trigo-
nal prism (itp). Distortions from the octahedral geometry for the
three complexes are at a minimum, as indicated by their CShM val-
ues. Moreover, the electronic effects from the central atom are less
important as it is a p block element. The steric demands of the sub-
stituents are solely responsible for the distortions reported in the
present study.
3.6. Bond valence sum
Bond valence sum (BVS) calculations offer a reliable method of
assigning a formal oxidation state to an atom in a compound from
the bond parameters. The method depends on the Rij value for an
iꢀj bond in a compound which is predominantly ionic [56–58]. In a
complex, the oxidation state of a central atom ‘i’ bonded to atom ‘j’
corresponds to the bond valence, sij, and the total valence of the
central atom corresponding to its oxidation state is
Rsij, where si-
Fig. 5. Distorted octahedral geometry (dOh) around indium.
j = exp[(Ro ꢀ Rij)/b] and Ro is a constant. The other constant b can
be assumed to be 0.37 [59,60]. BSV values were calculated for the
three complexes, giving 3.274, 3.299 and 3.316 for (1), (2) and (3)
respectively. The calculated BSVs are higher than the formal oxida-
tion state of +3 for indium. The higher values observed in the pres-
ent set of compounds support the fact that the In–S bonds are more
covalent and back bonding effects are highly pronounced.
dithiocarbamates vary between 25°, 35° and 37° for (1) 27°, 35°
and 43° for (2) and 45°, 47° and 50° for (3). The increase in the
twist angles is in line with the increased steric repulsions associ-
ated with the dicycohexyl analogue (3). The calculated chirality
values are 4.1438, 1.3746 and 1.1944 for (1), (2) and (3) respec-
tively. The observed values quantify the decrease in chirality with
increased steric repulsions. The three coordination environments
around indium are of a distorted octahedral geometry (dOh), as de-
picted in the Fig. 5. The CShM calculations of the three complexes
yielded the following values: 4.490485, 3.897557 and 5.138900 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 other two complexes
because of the largest steric demand associated with it. Between
the other two complexes, the ethyl analogue (2) is closer to an
3.7. Nano indium sulfide
3.7.1. Powder XRD and EDX
The powder XRD of the solvothermally prepared indium sulfide
is shown in Fig. 6, which indicates good crystallinity of the mate-
rial, and it is matched well with the JCPDS pattern reported for
b-In2S3 (PDF # 73-1366, 65-0459). The average size of the crystal-
line indium sulfide was 23 nm. The ease of formation of the nano-
sulfide followed the order: (3) > (1) > (2). An energy dispersive
Fig. 6. Powder XRD of the solvothermally prepared indium sulfide.

102
G.S. Sivagurunathan et al. / Polyhedron 72 (2014) 96–102
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