Nanoparticles and nanocrystals of a new bidentate nickel(II) complex of N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide: Synthesis, characterization, and crystal structures

Article abstract of DOI:10.1080/00958972.2012.744834

The nickel(II) complex of N-[ethyl(propan-2-yl)carbamothioyl]-4- nitrobenzamide has been synthesized and characterized by Fourier transform-infrared spectroscopy, elemental analysis, nuclear magnetic resonance spectroscopy, and mass spectrometry (atmospheric pressure chemical ionization mass spectrometry). The single-crystal X-ray structures of N-[ethyl(propan-2-yl) carbamothioyl]-4-nitrobenzamide (1) and bis[N-[ethyl(propan-2-yl)carbamothioyl]- 4-nitrobenzamide]nickel(II) (2) have been determined from single-crystal X-ray diffraction data. Loss of the N-H proton resonance and the N-H stretching vibration and the shift of the V_C=O and V_C=S stretching vibrations confirm formation of the metal complex. These studies show that the metal complex is neutral in cis-configuration. The complex has been used as a single-source precursor for the deposition of nickel sulfide nanocrystals by thermolysis. The nickel sulfide nanocrystals were characterized by X-ray powder diffraction and transmission electron microscopy.

Full text of DOI:10.1080/00958972.2012.744834

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Nanoparticles and nanocrystals
of a new bidentate nickel(II)
complex of N-[ethyl(propan-2-
yl)carbamothioyl]-4-nitrobenzamide:
synthesis, characterization, and crystal
structures
Sohail Saeed a , Naghmana Rashid a , Rizwan Hussain b , Jerry P.
Jasinski c , Amanda C. Keeley c & Sajid Khan d
a Department of Chemistry, Research Complex, Allama Iqbal Open
University, Islamabad, Pakistan
b National Engineering & Scientific Commission, Islamabad,
Pakistan
c Department of Chemistry, Keene State College, Keene, NH, USA
d School of Chemicals and Materials Engineering, National
University of Science and Technology, Islamabad, Pakistan
Accepted author version posted online: 06 Nov 2012.Version of
record first published: 18 Dec 2012.
To cite this article: Sohail Saeed , Naghmana Rashid , Rizwan Hussain , Jerry P. Jasinski , Amanda
C. Keeley & Sajid Khan (2013): Nanoparticles and nanocrystals of a new bidentate nickel(II)
complex of N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide: synthesis, characterization, and
crystal structures, Journal of Coordination Chemistry, 66:1, 126-138
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Journal of Coordination Chemistry
Vol. 66, No. 1, 10 January 2013, 126–138
Nanoparticles and nanocrystals of a new bidentate nickel(II)
complex of N-[ethyl(propan-2-yl)carbamothioyl]-4-
nitrobenzamide: synthesis, characterization, and crystal
structures
SOHAIL SAEEDy*, NAGHMANA RASHIDy, RIZWAN HUSSAINz, JERRY P.
JASINSKIx, AMANDA C. KEELEYx and SAJID KHAN{
yDepartment of Chemistry, Research Complex, Allama Iqbal Open University, Islamabad,
Pakistan
zNational Engineering & Scientific Commission, Islamabad, Pakistan
xDepartment of Chemistry, Keene State College, Keene, NH, USA
{School of Chemicals and Materials Engineering, National University of Science and
Technology, Islamabad, Pakistan
(Received 10 July 2012; in final form 19 September 2012)
The nickel(II) complex of N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide has been synthe-
sized and characterized by Fourier transform-infrared spectroscopy, elemental analysis, nuclear
magnetic resonance spectroscopy, and mass spectrometry (atmospheric pressure chemical ionization
mass spectrometry). The single-crystal X-ray structures of N-[ethyl(propan-2-yl)carbamothioyl]-4-
nitrobenzamide (1) and bis[N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide]nickel(II) (2)
have been determined from single-crystal X-ray diffraction data. Loss of the N–H proton resonance
and the N–H stretching vibration and the shift of the νC=O and νC=S stretching vibrations confirm
formation of the metal complex. These studies show that the metal complex is neutral in cis-config-
uration. The complex has been used as a single-source precursor for the deposition of nickel sulfide
nanocrystals by thermolysis. The nickel sulfide nanocrystals were characterized by X-ray powder
diffraction and transmission electron microscopy.
Keywords: Nickel complex; Crystal structure; Cis-configuration; Nanoparticles; Nanocrystals;
p-XRD; TEM
1. Introduction
Design and self-assembly of metal coordination polymers has received attention [1–5] for
crystallographic diversity and a myriad of applications [6, 7]. Although a variety of hybrid
polymers have been synthesized with intriguing architectures and physical properties, it is
still a challenge to prepare advanced conducting materials with predictable structures and
properties through combination of ligands with metal ions. Judicious selection of ligands
and suitable metal ions bearing the right coordination geometries is pivotal for designing
metal complexes for the fabrication of nanostructured thin films and nanoparticles.
*Corresponding author. Email: sohail262001@yahoo.com
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online Ó 2012 Taylor & Francis
http://dx.doi.org/10.1080/00958972.2012.744834

Nanoparticles and Nanocrystals of a New Bidentate Nickel(II) Complex
127
Thiourea chelating agents have been remarkable for analytical chemistry, especially for
the trace analysis of metals in complex matrices. Coordination chemistry and potential
applications of such ligands have only been explored to a small extent in the last few dec-
ades. With simultaneous presence of O, N, N', and S donors, substituted acylthiourea
ligands exhibit various coordination modes: (a) O and S bonded to M (monobasic bidentate)
[8], (b) only S bonded to M (neutral monodentate) [9], (c) O and N bonded to M (neutral
bidentate) [10], and (d) O and S bonded to M and N is bonded to M’ (monobasic bridging
ligand) [11]. Substituted acylthiourea ligands, which do not form an intramolecular hydro-
gen bond, tend to coordinate predominately bidentate (S and O) to transition metal ions
through sulfur and acyl oxygen [11]. Examples for this type of coordination are mononu-
clear complexes [ML2], where M = Ni(II), Cu(II), Co(II), Zn(II), Cd(II), Pt(II), and Pd(II)
and L= substituted acylthiourea derivatives [12]. Coordination solely through sulfur is rare
and occurs only for complexes with Au(I) [13], Ag(I) [14], Hg(II) [15], and Cu(I) [16]. It
has been suggested that intramolecular hydrogen bonding exists between the thiourea N–H
moiety (where R/R’=H) and the amidic O-donor to form a six-membered ring, with the con-
sequence that the ligands coordinate monodentate to metals through the sulfur donor [11].
There are relatively few reports on the deposition of nickel sulfide thin films from single-
source precursors by chemical vapor deposition. The phase diagram of the Ni–S system is
more complex than that of Fe or Co sulfides. In this system many crystalline phases and
stoichiometries have been reported including the following: Ni3+x S2, Ni3S2, Ni4+xS2, Ni6S5,
Ni7S6, Ni9S8, NiS, Ni3S4, and NiS2 [17–19]. Some compounds, e.g. NiS and NiS2, have
been studied extensively, while for others only limited information is available. The NiS2
(Vaesite) is a p-type semiconductor with a band gap of 0.5 eV [20], potentially useful in
photo electrochemical solar cells [21, 22], IR detectors [23], catalysis [24], and sensors
[25]. It is also used as a hydrodesulfurization catalyst and as a cathode material in recharge-
able lithium batteries [26]. Nomura et al. studied the growth of NiS1.03 from [Ni
(S2CNEt2)2] on silicon (111) substrates by low-pressure chemical vapor deposition (LP-
CVD) [27]. Earlier, O’Brien et al. reported the deposition of nickel sulfide films from
dithiocarbamate compounds of the type [Ni (S2CNRR’)2], where RR’= Et2, MeEt, MenBu,
or MenHex, by AA [28] and LP-CVD methods [29] and also from xanthate compounds of
i
the type [Ni(S2COR)2], where R = Et or Pr, by aerosol-assisted chemical vapor deposition
(AACVD) [30]. Recently, Alam et al. used pyridine adducts of nickel(II) xanthates as sin-
gle-source precursors for the deposition of nickel sulfide thin films by AACVD [31].
Our team has focused on the synthesis, characterization, crystal structures, biological
activities, and material applications of new thiourea derivatives and their metal complexes
[32–36]. In this communication, we have synthesized N-[ethyl(propan-2-yl)carbamothioyl]-
4-nitrobenzamide (1) and bis[N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide]nickel
(II) (2) and characterized each by spectroscopic techniques and crystal structures. In addi-
tion, the metal complex has been used as a single-source precursor for the deposition of
nickel sulfide nanoparticles and nanocrystals by thermolysis.
2. Experimental
2.1. Materials and reagents
Analytical grade 4-nitrobenzoyl chloride (≥98.0%), ethyl isopropyl amine (99%), sodium
thiocyanate (99%), nickel(II) acetate tetrahydrate (99%), and tetrabutylammonium bromide

128
S. Saeed et al.
(TBAB) (≥98%) were purchased from Sigma-Aldrich. Analytical grade solvents, such as
tetrahydrofuran (THF), toluene, acetonitrile, n-hexane, dichloromethane, ethanol, methanol,
chloroform, ethyl acetate, and others, were purchased from Sigma-Aldrich and Riedal-
deHaen (Germany); ethanol and acetone were dried using standard procedures [37]. All
manipulations were carried out in air except for thermolysis experiments. The synthesis of
nickel sulfide nanoparticles and nanocrystals was carried out under N2.
2.2. Physical measurements
Elemental analysis was performed by the University of Manchester micro-analytical labo-
ratory. Infrared spectra were recorded on a Specac single-reflectance Attenuated Total
Reflectance instrument (4000–400 cmꢀ1, resolution 4 cmꢀ1). Atmospheric pressure chemi-
cal ionization mass spectrometry of the ligand and nickel complex (MS-APCl) was
recorded on a Micromass Platform II instrument. Metal analysis of the complex was car-
ried out by Thermo iCap 6300 inductively coupled plasma optical emission spectroscopy.
Melting points were recorded on a Barloworld SMP10 melting point apparatus. Thermal
stability of the nickel complex was studied by thermogravimetry in an inert atmosphere, at
a sample heating rate of 283 K minꢀ1, with a DuPont 2000 ATG. X-ray powder diffraction
studies were performed on a Xpert diffractometer using Cu–Kα radiation. The samples
were mounted flat and scanned between 20 and 65° with a step size of 0.05 with various
count rates. The diffraction patterns were then compared to documented patterns in the
International Center Diffraction Data (ICDD) index. Transmission electron microscopy
(TEM) samples were prepared by evaporating a drop of a dilute suspension of the sample
in n-hexane on a carbon-coated copper grid. Excess solvent was allowed to dry completely
at room temperature. Transmission electron microscopic images were collected on a Philips
CM200 transmission electron microscope using an accelerating voltage of 200 kV.
2.3. Synthesis of the ligand and nickel complex
2.3.1. Synthesis of N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide (1).
A
solution of p-nitrobenzoyl chloride (0.01 mol) in anhydrous acetone (80 mL) and 3% TBAB
in acetone was added dropwise to a suspension of sodium thiocyanate in acetone (50 mL)
and the reaction mixture was refluxed for 45 min. After cooling to room temperature, a solu-
tion of ethyl isopropyl amine (0.01 mol) in acetone (25 mL) was added and the resulting mix-
ture was refluxed for 2 h. The reaction mixture was poured into five times its volume of cold
water, whereupon the thiourea precipitated. The solid product was washed with water and
purified by re-crystallization from an ethanol–dichloromethane mixture (1 : 2) giving light
yellow crystals. M.p.: 418–419 K. Yield: 2.7 g (76%). IR (νmax/cmꢀ1): 3226 (NH), 2944,
1
2867 (C–H), 1671 (C=O), 1259 (C=S). H nuclear magnetic resonance (NMR) (400 MHz,
CDCl3) in δ (ppm): 8.40 (br s, 1H, CONH), 8.28 (d, 2Hmeta, p-nitrophenyl), 8.01 (d, 2Hortho
,
p-nitrophenyl), 4.03 (q, 2H, N–CH2), 3.72 (m, H, N–CH), 1.38 (t, 3H,–CH3), 1.29 (s, 6H, –
CH3); Anal. Calcd for C13H17N3O3S: C, 52.86; H, 5.80; N, 14.23; S, 10.86. Found: C,
52.84; H, 5.84; N, 14.21; S, 10.87. Mass (MS-APCI) (major fragment, m/z): 295[M+,
C13H17N3O3S].
2.3.2. Synthesis of bis[N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide]nickel
(II) (2). A solution of nickel acetate (0.01 mol) in methanol (35 mL) was added dropwise

Nanoparticles and Nanocrystals of a New Bidentate Nickel(II) Complex
129
to a solution of the ligand in a 1 : 2 ratio with a small excess of ligand in ethanol (35 mL)
at room temperature, and the resulting mixture was stirred for 3 h. The reaction mixture
was filtered, washed with ethanol, and re-crystallized from a THF/acetonitrile mixture
(1 : 1) giving yellowish golden crystals. M.p.: 431–432 K. Yield: 3.5 g (82%). IR (νmax
/
cmꢀ1): 2927, 2853(Ar–H), 1508(C–O), 1533(C–N), 1142(C–S); Anal. Calcd for
C26H32N6O6S2Ni: C, 48.24; H, 4.98; N, 12.98; S, 9.91; Ni, 9.07. Found: C, 48.51; H,
1
4.95; N, 12.87; S, 9.94; Ni, 8.98. H NMR (400 MHz, CDCl3) in δ (ppm): 8.28 (d, 4Hmeta
,
p-nitrophenyl), 8.01 (d, 4Hortho, p-nitrophenyl), 4.05 (m, 4H, N–CH2), 3.70 (m, 2H, N–
CH), 1.35 (t, 6H, –CH3), 1.28 (s, 12H, –CH3); Mass (MS-APCI) (major fragment, m/z):
647[M+, C26H32N6O6S2Ni].
2.4. X-ray structure determination
A crystal of 1 was mounted on a loop and placed in a 173 K compressed air stream on an
Agilent Gemini-EOS single-crystal autodiffractometer at Keene State College (Keene,
NH). Crystallographic data were collected using graphite monochromated 0.71073 Å Mo–
Kα radiation and integrated and corrected for absorption using the CrysAlisRed (Oxford
Diffraction, 2010 software package) [38]. The structures were solved using direct methods
and refined using least-square methods on F2 [39]. All non-hydrogen atoms were refined
anisotropically. Hydrogens were included in calculated positions, assigned isotropic ther-
mal parameters, and allowed to ride on their parent carbons. All other pertinent crystallo-
graphic details, such as h, k, l ranges, 2h ranges, and R-factors, can be found in table 1.
2.5. Synthesis of nickel sulfide nanoparticles/nanocrystals
Nickel sulfide nanocrystals were prepared by pyrolyzing the nickel complex in oleylamine.
In a typical reaction, 15 mL of oleylamine was refluxed under vacuum at 363 K for 45 min
and then purged by nitrogen gas for 30 min, at same temperature. Precursor (0.3 g) was
added into hot oleylamine and the reaction temperature was slowly increased to 443 or
503 K. The temperature was maintained for 1 h and the mixture was allowed to cool to
room temperature. Addition of 30 mL methanol produced a black precipitate which was
separated by centrifugation. The black residue was washed twice by methanol and dis-
persed in toluene or hexane for further characterizations.
3. Results and discussion
3.1. Synthesis and spectroscopic characterization
The thiourea derivative and its nickel complex were synthesized according to the reported
procedure [40–45] with minor modifications as presented in Synthesis Scheme 1. The use of
a phase transfer catalyst (PTC) as a method of agitating a heterogeneous reaction system is
gaining recognition [46, 47]. In search of improving methods to prepare the target thiourea
by reacting isothiocyanates with nucleophiles, we have found that the use of TBAB as PTC
can produce isothiocyanates in good yield. The reaction proceeds via nucleophilic addition
of the secondary amine to the isothiocyanate. We have conducted our reaction using TBAB
as a PTC to synthesize the thiourea derivatives. Solid-state IR spectra of the thiourea

130
S. Saeed et al.
Table 1. Crystal data and structure refinement for 1 and 2.
Compound 1
Compound 2
CCDC
884,824
C13H17N3O3S
295.36
884,825
C26H32N6O6S2Ni
647.41
Empirical formula
Formula weight
Temperature
173(2) K
173(2) K
Wavelength
1.54184 Å
1.54184 Å
Crystal system
Space group
Unit-cell dimensions
Triclinic
Pꢀ1
Orthorhombic
F d d 2
a = 7.5483(6) Å
b = 13.2927(9) Å
c = 15.2278(12) Å
β = 96.700(6)°
1471.65(19)Å3
4
a = 24.8021(7) Å
b = 16.5410(6) Å
c = 14.3279(4) Å
β = 90°
Volume
Z
5878.1(3) Å3
8
Density (calculated)
Absorption coefficient
F(0 0 0)
Crystal size
Theta range for data
collection
1.333 Mg mꢀ3
2.060 mmꢀ1
624
1.463 Mg mꢀ3
2.711 mmꢀ1
2704
0.34 ꢁ 0.28 ꢁ 0.08 mm3
2.9918 to 71.4707°
0.44 ꢁ 0.42 ꢁ 0.22 mm3
4.45 to 71.61°
Index ranges
ꢀ9 < = h < = 9, ꢀ16 < = k < = 14, ꢀ18 < ꢀ30 < = h < = 30, ꢀ15 < = k < = 20, ꢀ17 <
= l < = 18
9437
= l < = 17
9538
Reflections collected
Independent reflections
Completeness to
theta = 67.50°
Refinement method
Data/restraints/
5581 [R(int) = 0.0422]
99.5%
2761 [R(int) = 0.0216]
100.0%
Full-matrix least-squares on F2
5581/0/376
Full-matrix least-squares on F2
2761/1/200
parameters
Goodness-of-fit on F2
Final R indices
1.052
1.057
R1 = 0.0651, wR2 = 0.1767
R1 = 0.0355, wR2 = 0.0964
[I > 2sigma(I)]
R indices (all data)
Extinction coefficient
Largest diff. peak and
hole
R1 = 0.0738, wR2 = 0.1864
0.0013(5)
R1 = 0.0368, wR2 = 0.0975
0.00(2)
0.525 and ꢀ0.422 e.Åꢀ3
0.531 and ꢀ0.233 e.Åꢀ3
derivative and the metal complex at 4000–400 cmꢀ1 were compared and assigned by com-
parison [48]. N,N'-disubstituted thioureas behave both as monodentate and as bidentate
ligands depending on the reaction conditions. Characteristic bands of N,N'-disubstituted
thioureas are 3226 (NH), 2867, 2944 Ph (CH), 1671 (C=O), and 1259 (C=S), and there is a
slight shift of C=O and C=S stretches due to coordination of the ligands to nickel.
Acylthioureas usually are bidentate to transition metal ions through the acyl oxygen and
sulfur [49–51]. Fourier transform-infrared (FT-IR) spectra of the complex show significant
changes compared with FT-IR spectra of the corresponding ligand. IR spectra of the com-
plex show absorptions at υmax/cmꢀ1 2853–2927 Ph (CH), 1508 (C–O), 1533 (C–N), and
1142 (C–S). The most striking changes are N–H stretches at 3226 cmꢀ1 in the free ligand,
which disappears completely, in agreement with both ligand and complex structures. This
indicates that the loss of proton comes from nitrogen of the (NH–CO) amide. Another
striking change is observed with the carbonyl stretch. Vibration of carbonyl (1671 cmꢀ1
)
in the free ligand shifts to lower frequency upon complexation confirming that the ligand
is coordinated to nickel(II) through oxygen and sulfur [52–56]. A comparative absorption
pattern of the complex with the values of the free ligand demonstrates that coordination of
a thiourea to nickel has a significant effect on υ(NH), υ(CO), and υ(CS).

Nanoparticles and Nanocrystals of a New Bidentate Nickel(II) Complex
131
Scheme 1. Preparation of 1 and 2.
1H NMR data for N,N'-disubstituted thiourea show that the NH resonates downfield.
The proton chemical shifts are 8.40 for free NH and the aromatic protons appear downfield
between 7.35 and 8.32 ppm. Coordinating or highly polar solvents like DMSO-d6 have
profound effects on free NH proton chemical shifts and appear more downfield compared
with C6D6, CDCl3, and CD2Cl2. This shift can be attributed to hydrogen bonding between
1
the NH and the sulfoxide (S=O). H NMR data for the metal complex show aromatic pro-
tons at 8.28–8.01 ppm as reported earlier [57, 58]. Resonances due to NH of CONH in 1
completely disappear in 2. This indicates that the loss of the proton was originally bonded
to nitrogen of amide in the ligand and confirms the formation of the nickel complex. All
characteristic chemical shifts were identified by their intensity and multiplicity patterns.

132
S. Saeed et al.
Figure 1. Perspective view of the two independent molecules in the asymmetric unit of 1 with atom-labeling
scheme and 30% probability ellipsoids.
Figure 2. Perspective view of 2 which resides around a crystallographic inversion center on Ni1, and with atom-
labeling scheme and 30% probability ellipsoids.

Nanoparticles and Nanocrystals of a New Bidentate Nickel(II) Complex
Table 2. Selected bond lengths (Å) and angles (°) for 1 and 2.
Bond lengths (Å)
133
Compound 1
Compound 2
S(1B)–C(8B)
O(1A)–N(1A)
O(1B)–N(1B)
O(2A)–N(1A)
O(2B)–N(1B)
O(3A)–C(7A)
O(3B)–C(7B)
N(1A)–C(1A)
N(1B)–C(1B)
N(2A)–C(7A)
N(2A)–C(8A)
N(2A)–H(2NA)
N(2B)–C(7B)
N(2B)–C(8B)
N(2B)–H(2NB)
N(3A)–C(8A)
N(3A)–C(9A)
N(3A)–C(11A)
N(3B)–C(8B)
N(3B)–C(9B)
N(3B)–C(11B)
1.651(3)
1.225(4)
1.224(3)
1.219(4)
1.231(4)
1.212(3)
1.217(3)
1.483(4)
1.474(3)
1.367(3)
1.427(3)
0.84(3)
1.367(3)
1.428(3)
0.84(4)
1.331(4)
1.474(3)
1.481(4)
1.337(4)
1.470(4)
1.487(4)
Ni(1)–O(3A)#1
1.810(13)
1.810(14)
1.899(15)
2.1429(8)
2.1430(8)
1.757(3)
1.208(4)
1.210(4)
1.481(4)
1.302(4)
1.490(4)
1.374(4)
1.382(4)
0.9300
Ni(1)–O(3A)
Ni(1)–O(3B)
Ni(1)–S(1)
Ni(1)–S(1)#1
S(1)–C(8)
O(1)–N(1)
O(2)–N(1)
N(1)–C(1)
N(2)–C(7)
N(3)–C(9)
C(1)–C(6)
C(3)–C(4)
C(3)–H(3)
O(1)–N(1)–C(1)
O(2)–N(1)–C(1)
C(7)–N(2)–C(8)
C(8)–N(3)–C(11)
C(8)–N(3)–C(9)
C(11)–N(3)–C(9)
C(6)–C(1)–C(2)
118.5(3)
118.0(2)
123.3(2)
123.6(2)
119.1(3)
117.0(2)
122.5(3)
Bond angles (°)
O(2A)–N(1A)–O(1A)
O(2A)–N(1A)–C(1A)
O(1A)–N(1A)–C(1A)
O(1B)–N(1B)–O(2B)
O(1B)–N(1B)–C(1B)
O(2B)–N(1B)–C(1B)
C(7A)–N(2A)–C(8A)
C(7A)–N(2A)–H(2NA)
C(8A)–N(2A)–H(2NA)
C(7B)–N(2B)–C(8B)
C(7B)–N(2B)–H(2NB)
C(8B)–N(2B)–H(2NB)
C(8A)–N(3A)–C(9A)
C(8A)–N(3A)–C(11A)
C(9A)–N(3A)–C(11A)
C(8B)–N(3B)–C(9B)
C(8B)–N(3B)–C(11B)
C(9B)–N(3B)–C(11B)
C(2A)–C(1A)–C(6A)
C(2A)–C(1A)–N(1A)
C(6A)–C(1A)–N(1A)
C(6B)–C(1B)–C(2B)
124.4(3)
O(3A)#1–Ni(1)–O(3A)
O(3A)#1–Ni(1)–O(3B)
O(3A)–Ni(1)–O(3B)
O(3A)#1–Ni(1)–O(3B)#1
O(3A)–Ni(1)–O(3B)#1
O(3B)–Ni(1)–O(3B)#1
O(3A)#1–Ni(1)–S(1)
O(3A)#1–Ni(1)–S(1)#1
O(3A)–Ni(1)–S(1)#1
S(1)–Ni(1)–S(1)#1
73.8(10)
80.3(17)
18.2(3)
18.2(3)
80.3(17)
118.4(3)
117.1(3)
123.8(3)
118.5(3)
117.8(3)
120.1(2)
119(2)
116(2)
118.1(2)
120(2)
91(2)
169.9(11)
97.0(6)
169.9(11)
92.45(4)
107.24(9)
128.6(17)
123.5(3)
109.5
C(8)–S(1)–Ni(1)
C(7)–O(3B)–Ni(1)
O(1)–N(1)–O(2)
113(2)
119.1(2)
123.1(2)
117.5(2)
118.4(3)
123.9(2)
117.6(2)
122.9(3)
118.7(3)
118.4(3)
122.9(3)
H(10A)–C(10)–H(10C)
H(10B)–C(10)–H(10C)
C(13)–C(11)–N(3)
C(13)–C(11)–C(12)
N(3)–C(11)–C(12)
C(13)–C(11)–H(11)
N(3)–C(11)–H(11)
C(12)–C(11)–H(11)
C(11)–C(12)–H(12A)
109.5
109.3(3)
114.0(3)
111.5(3)
107.2
107.2
107.2
109.5
Table 3. Weak intermolecular interactions for 1 [Å and °].
D–H…A
d(D–H)
d(H…A)
d(D…A)
\(DHA)
N2A–H2NA…S1B#1
N2B–H2NB…S1A#2
C10A–H10A…S1B#3
C11B–H11B…O2B#4
0.84(3)
0.84(4)
0.96
2.55(3)
2.56(4)
2.85
3.351(2)
3.329(2)
3.727(4)
3.359(4)
161(3)
153(3)
153.1
141.8
0.98
2.53
Notes: Symmetry transformations used to generate equivalent atoms: #1 x, yꢀ1, z; #2 x, y + 1, z; #3 x + 1, yꢀ1,
z; and #4 ꢀx + 1, ꢀy + 1, ꢀz + 1.

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S. Saeed et al.
3.2. Single-crystal X-ray crystallography
The molecular structures of N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide (1) and
bis[N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide]nickel(II) (2) are shown in
figures 1 and 2, respectively. Crystal data, refinement parameters, and selected bond
lengths and angles are listed in tables 1 and 2, respectively. The structure of the nickel
complex is in a cis-configuration with a slightly distorted square planar coordination of
nickel by two oxygens and two sulfurs.
In 1, there are two independent molecules in the asymmetric unit. Bond lengths are in
normal ranges [59]. The mean plane of the nitro (C1A/N1A/O1A/O2A and C1B/N1B/
O1B/O2B) is twisted by 2.4(4)° or 3.5(4)° with the mean plane of the benzene ring. The
amide groups (C4A/C7A/O3A/N2A and C4B/C7B/O3B/N2B) and the thionyl groups
(N1A/C8A/S1A/N3A and N1B/C8B/S1B/N3B) are twisted by 14.7(4)° or 12.5(1)° and
89.7(0)° or 87.4(5)° with the mean plane of the benzene ring, respectively. Crystal packing
is stabilized by weak C–H…O intermolecular interactions (table 3, figure 3).
Figure 3. Packing diagram of 1 viewed along the a axis. Dashed lines indicate weak N–H…S, C–H…S, and C–
H…O intermolecular interactions. Remaining hydrogens have been removed for clarity.
Table 4. Weak intermolecular interactions for 2 [Å and °].
D–H…A
d(D–H)
d(H…A)
d(D…A)
(DHA)
C2–H2…O3B#1
C5–H5…O1#2
0.93
0.93
2.51
2.49
3.34(3)
3.284(4)
149.1
143.7
Notes: Symmetry transformations used to generate equivalent atoms: #1 x + 1/4, ꢀy + 5/4, z + 1 and #2 xꢀ1/4,
4
ꢀy + 5/4, zꢀ1/4.

Nanoparticles and Nanocrystals of a New Bidentate Nickel(II) Complex
135
Figure 4. Packing diagram of 2 viewed along the a axis. Hydrogens have been removed for clarity.
In 2, the molecule resides around a crystallographic inversion center on nickel. Bond
lengths are in normal ranges [59]. The oxygen in carbamothioyl is disordered over two
sites with occupancies of 0.42(10) (O3A) and 0.58(10) (O3B). The six-membered car-
bamothioyl groups (Ni1/O3A/C7/N2/C8/S1 and Ni1/O3B/C7/N2/C8/S1) adopt a slightly
distorted boat or envelope conformation with puckering parameters Q, h, and of 0.249(9)
Å, 93(3)°, 236(3)° or 0.46(2) Å, 128(2)°, 170(3)°, respectively [60]. The mean plane of the
nitro (C1/N1/O1/O2) is twisted by 5.4(4) Å with the mean plane of the benzene ring. The
dihedral angle between the mean planes of the benzene rings is 16.0(9) Å. Crystal packing
is stabilized by weak C–H…O intermolecular interactions (table 4, figure 4).
3.3. Thermal decomposition studies and characterization of nickel sulfide nanoparticles
and nanocrystals deposited from 2
Thermal behavior of 2 has been examined by thermal gravimetric analysis (TGA) per-
formed under an inert atmosphere of flowing nitrogen (20 mL/min) and a heating rate of
283 K/min. TGA of 2 shows two-step decomposition with rapid weight loss between 506
and 598 K and the second step between 601 and 848 K (table 5). The major part of the

136
S. Saeed et al.
Table 5. Thermogravimetric analysis of 2.
First-stage decomposition temperature range (K): 506–598
Second-stage decomposition temperature range (K): 601–848
Maximum degradation temperature range (K): 553–593
Weight loss at 1st stage decomposition (%): 62
Weight loss at 2nd stage decomposition (%): 16
Residual weight at 873 K (%): 18.63
200
180
160
140
120
100
80
60
40
(b)
(a)
20
0
30
40
50
60
70
80
90
2-Theta-Scale (deg)
Figure 5. XRD pattern of NiS nanoparticles/nanocrystals prepared at (a) 443 K and (b) 503 K from precursor 2.
Figure 6. TEM image of nickel sulfide nanoparticles and nanocrystals prepared from precursor 2 at 503 K.

Nanoparticles and Nanocrystals of a New Bidentate Nickel(II) Complex
137
complex degraded sharply at 553–593 K leaving residual amount of 18.63% which is close
to the mass of NiS (calc. 19.04%). The XRD pattern for the NiS nanocrystals synthesized
from 2 is shown in figure 5. The synthesis of the nickel sulfide nanoparticles and nanocrys-
tals was carried out at 443 and 503 K. No deposition was obtained below 443 K. The mate-
rial was almost in non-crystalline form at this low temperature. At 503 K, the XRD pattern
of NiS nanocrystals shows diffraction patterns of hexagonal NiS and the space group P63/
mmc with major diffraction peaks of (1 0 0), (1 0 1), (1 0 2), and (11 0) planes (ICDD: 00-
002-1280). The TEM image (figure 6) showed the particles to be hexagonal and trigonal
crystallites. A certain degree of agglomeration occurred, whereby the size of the nanoparti-
cles could be approximated to 10–18 nm in length and nanocrystals to 1250 nm.
4. Conclusions
We have synthesized an unsymmetrical thiourea, N-[ethyl(propan-2-yl)carbamothioyl]-4-
nitrobenzamide (1), and its nickel complex, bis[N-[ethyl(propan-2-yl)carbamothioyl]-4-
nitrobenzamide] nickel(II) (2). The single-crystal X-ray structures of 1 and 2 have been
determined. Complex 2 was used as a single-source precursor for the deposition of nickel
sulfide nanoparticles (trigonal crystallites 10–18 nm in length) and nanocrystals (hexagonal
crystallites 1250 nm in length).
Supplementary crystallographic data
Crystallographic data for the structure reported in this article have been deposited with the
Cambridge Crystallographic Data Center, CCDC 884,824 (1) and 884,825 (2). Copies of
this information may be obtained free of charge from the Director, CCDC, 12 Union Road,
Cambridge, CBZ IEZ, UK. Facsimile (44) 01223 336 033, E-mail: deposit@ccdc.cam.ac.
uk or http://www.ccdc.cam.ac.uk/deposit.
Acknowledgment
The authors are thankful to Dr. Alan Harvey, School of Materials Science, The University
of Manchester, UK for helping in Transmission Electron Microscopy (TEM) image. JPJ
acknowledges the NSF-MRI program (grant No. CHE1039027) for funds to purchase the
X-ray diffractometer.
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