Synthesis, spectral (IR, UV-Vis and variable temperature NMR) characterization and crystal structure of (N-benzyl-N-furfuryldithicarbamato-S, S')(thiocyanato-N)(triphenylphosphine)nickel(II)

Article abstract of DOI:10.1016/j.saa.2014.03.068

Planar (N-benzyl-N-furfuryldithiocarbamato-S,S')(thiocyanato-N) (triphenylphospine)nickel(II), [Ni(bfdtc)(NCS)(PPh₃)], (1) was prepared from bis(N-benzyl-N-furfuryldithiocarbamato-S,S')nickel(II), [Ni(bfdtc)₂], (2) and characterized by elemental analysis, cyclic voltammetry, electronic, IR and variable temperature ¹H and ¹³C NMR spectra. For complex 1, the thioureide vCN value is shifted to higher wavenumber compared to 2 and N¹³CS₂ carbon signal observed for 1 is additionally shielded compared to the parent complex 2, suggesting increased strength of the thioureide bond due to the presence of the π-accepting phosphine. In the room temperature ¹³C NMR spectrum of 1, two pseudo doublets are observed in the aliphatic region. Variable temperature ¹³C NMR spectral studies suggest that the fast thiocyanate exchange appears to be responsible for the appearance of pseudo doublets. Single crystal X-ray structural analysis of 1 and 2 confirm the presence of four coordinated nickel in a distorted square planar arrangement with the NiS₂PN and NiS₄ chromophores, respectively. The NiS bonds are symmetric in 2 (2.1914(14) and 2.2073(13) A?). But significant asymmetry in NiS bond distances was observed in 1 (2.2202(8) A? and 2.1841 A?). This observation clearly supports the less effective trans effect of SCN^- over PPh₃. Cyclic voltammetric studies revealed easier reduction of nickel(II) to nickel(I) in complex 1 compared to 2.

Full text of DOI:10.1016/j.saa.2014.03.068

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 285–292
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, spectral (IR, UV–Vis and variable temperature NMR)
characterization and crystal structure
of (N-benzyl-N-furfuryldithicarbamato-S,S0)
(thiocyanato-N)(triphenylphosphine)nickel(II)
b
b
P. Valarmathi a, S. Thirumaran a, , Lovely Sarmal , Rajni Kant
⇑
a Department of Chemistry, Annamalai University, Annamalainagar, Tamil Nadu 608 002, India
b X-ray Crystallography Laboratory, Post-Graduate Department of Physics & Electronics, University of Jammu, Jammu Tawi 180 006, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Ni(bzfdtc)(NCS)(PPh3) (1) (bzfdtc = N-
benzyl-N-furfuryldithiocarbamate)
was prepared.
1 was characterized by IR, UV–Vis, CV,
variable temp. NMR and X-ray
diffraction.
Ni2+ in 1 exists within a S2PN donor
set that defines a square planar
geometry.
In CHCl3 solution of 1, thiocyanate
exchange process occurs at room
temperature.
NiAS bonds in 1 are asymmetric due
to the difference in trans effect of
PPh3 and NCSꢁ.
a r t i c l e i n f o
a b s t r a c t
(N-benzyl-N-furfuryldithiocarbamato-S,S0)(thiocyanato-N)(triphenylphospine)nickel(II),
[Ni
Article history:
Planar
(bfdtc)(NCS)(PPh3)], (1) was prepared from bis(N-benzyl-N-furfuryldithiocarbamato-S,S0)nickel(II),
[Ni(bfdtc)2], (2) and characterized by elemental analysis, cyclic voltammetry, electronic, IR and variable
temperature 1H and 13C NMR spectra. For complex 1, the thioureide vCAN value is shifted to higher
wavenumber compared to 2 and N13CS2 carbon signal observed for 1 is additionally shielded compared
to the parent complex 2, suggesting increased strength of the thioureide bond due to the presence of the
Received 26 January 2014
Received in revised form 9 March 2014
Accepted 21 March 2014
Available online 31 March 2014
Keywords:
Dithiocarbamate
Nickel(II)
Crystal structure
Variable temperature NMR spectra
p
-accepting phosphine. In the room temperature 13C NMR spectrum of 1, two pseudo doublets are
observed in the aliphatic region. Variable temperature 13C NMR spectral studies suggest that the fast
thiocyanate exchange appears to be responsible for the appearance of pseudo doublets. Single crystal
X-ray structural analysis of 1 and 2 confirm the presence of four coordinated nickel in a distorted square
planar arrangement with the NiS2PN and NiS4 chromophores, respectively. The NiAS bonds are symmet-
ric in 2 (2.1914(14) and 2.2073(13) Å). But significant asymmetry in NiAS bond distances was observed in
1 (2.2202(8) Å and 2.1841 Å). This observation clearly supports the less effective trans effect of SCNꢁ over
PPh3. Cyclic voltammetric studies revealed easier reduction of nickel(II) to nickel(I) in complex 1
compared to 2.
Ó 2014 Published by Elsevier B.V.
⇑
Corresponding author. Tel.: +91 9842897597.
E-mail address: sthirumaran@yahoo.com (S. Thirumaran).
http://dx.doi.org/10.1016/j.saa.2014.03.068
1386-1425/Ó 2014 Published by Elsevier B.V.

286
P. Valarmathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 285–292
Introduction
Dithiocarbamate complexes of various metal ions are used in
analytical chemistry [1,2], organic synthesis [3], medicine [4], biol-
ogy [5], as oxidants of organic molecules [6], polymer photostabi-
lizers [7], and precursors for preparing metal sulfide nanoparticles
[8,9]. Optical and electrochemical properties of metal-dithiocarba-
mate complexes favour the creation of cation, anion and neutral
molecule sensors [10–13]. Nickel(II) complexes of the type Ni(dtc)2
have a mononuclear square planar structure [14]. Ni(dtc)2 com-
plexes are found to show interesting variations in reactivity
towards soft Lewis bases such as phosphines [15] and hard bases
such as nitrogenous ligands [16]. Complexes containing the NiXS2P
chromophore have shown catalytic activity, especially for oligo-
merization of olefins [17,18]. In the dithiocarbamate complexes,
the R1, R2 groups in the S2CNR1R2 moiety influence the stability,
structure, physico-chemical and biological properties of the com-
plexes [19]. Suitable changes in substituents at the nitrogen of
dithiocarbamate can markedly affect the properties of the
complexes [20]. At room temperature, no ligand exchange
process was observed in [Ni(dtc)(NCS)(PPh3)] [4]. In the case of
[Ni(S2CNR2)(PPh3)X] (R = Et and X = Cl, I, SCN), the ligand (X)
exchange process was observed at low temperature (ꢁ60 °C)
[21]. The aim of the present work was a detailed study of the coor-
dination complex 1 to investigate the ligand exchange process and
to determine the effect of P-donor atom on the structure. In this
paper, we report synthesis, cyclic voltammetry, spectral and struc-
tural studies on complexes 1 and 2. The study of ligand exchange
process using variable temperature NMR spectra is also presented.
Scheme 1. Preparation of 1.
Experimental
times with cold water and then dried [23]. Single crystals suitable
for X-ray structure analysis were obtained by the recrystallization
from a solution of the substance in a mixture of dichloromethane-
acetonitrile (1:1).
General
IR (KBr, cmꢁ1):
m
= 1499 (
mCAN), 1012 (mCAS). UV–Vis (CHCl3, nm):
All reagents and solvents were commercially available high-
grade materials (Merck/sd Fine/Hi media) and used as received. A
Shimadzu UV-1650 PC double beam UV–Vis spectrometer was
used for recording the electronic spectra. The spectra were re-
corded in CHCl3 and the pure solvent was used as the reference.
Cyclic voltammograms were recorded on a CHI604C Electrochem-
ical Analyzer. The working electrode was platinum. The counter
electrode was platinum wire, and reference electrode was Ag/AgCl.
Pure dichloromethane was used as the solvent and tetrabutylam-
monium perchlorate as the supporting electrolyte. The scan rate
was 100 mVsꢁ1. All the measurements were recorded at room tem-
perature (27 °C) in an oxygen free atmosphere, provided by bub-
bling purified nitrogen through the solution. IR spectra were
recorded on a Thermo Nicolet Avatar 330 FT-IR spectrophotometer
(range 400–4000 cmꢁ1) as KBr pellets. Elemental analysis was per-
formed using Perkin Elmer 2400 series II CHN analyzer. The NMR
spectra were recorded on AV-III 400 NMR spectrometer operating
at 400 MHz.
c
= 642, 489, 430, 390, 326, 256. 1H NMR (400 MHz, CDCl3, ppm):
d = 4.67 (s, NACH2AC6H5), 4.82 [s, CH2 (furfuryl)], 6.38–7.42 (aro-
matic protons). 13C NMR (101 MHz, CDCl3, ppm): d = 43.4 (NA
CH2AC6H5), 51.3 [CH2 (furfuryl)], 110.7, 110.8, 143.1, 147.5 (furyl
ring carbons), 128.4–133.9 (phenyl ring carbons), 209.4 (NCS2).
Preparation of complex [Ni(bfdtc)(NCS)(PPh3)] (1)
A mixture of [Ni(bfdtc)2] (1.0 mmol, 0.583 g), PPh3 (2.0 mmol,
0.524 g), NiCl2ꢂ6H2O (1.0 mmol, 0.238 g) and NH4SCN (2.0 mmol,
0.152 g) was refluxed for 3 h in chloroformAmethanol solvent mix-
ture (1:1, 50 mL). The purple-red solution obtained was filtered
and left for evaporation. After 2 days, a purple-red solid separated
out. Single crystals suitable for X-ray structural analysis were ob-
tained by the recrystallization from dichloromethane-acetonitrile
(1:2) solvent mixture (Scheme 1).
Yield: 58%, mp 188 °C. IR (KBr, cmꢁ1):
m
= 2094 (NCS), 1514
(m
CAN), 1017 ( CAS). UV–Vis (CHCl3, nm): c
m
= 485, 331, 251. 1H
NMR (400 MHz, CDCl3, ppm): d = 4.44–4.76 (four broad signals
overlapped to appear as a triplet, CH2), 6.17–7.78 (aromatic pro-
tons). 13C NMR (101 MHz, CDCl3, ppm): d = 43.2, 43.6 (NACH2A
C6H5), 51.2, 51.7 [CH2 (furfuryl)], 110.7, 111.3, 143.3, 146.7 (furyl
ring carbons), 143.9 (NCS), 127.8–134.1 (phenyl ring carbons),
206.0 (NCS2). 31P NMR (CDCl3, ppm): d = 22.2 (PPh3). Anal. Calcd.
for C32H27N2S3OPNi (%): C, 59.92; H, 4.24; N, 4.37. Found (%): C,
59.84; H, 4.16; N, 4.37.
Preparation of Complexes
Preparation of amine
N-Benzyl-N-furfurylamine was prepared by general methods
reported earlier [22].
Preparation of [Ni(bfdtc)2] (2)
N-Benzyl-N-furfurylamine (4.0 mmol, 0.75 g) in ethanol was
mixed with carbon disulfide (4.0 mmol, 0.3 mL) under ice cold con-
dition. To the resultant yellow dithiocarbamic acid solution, aque-
ous solution of NiCl2ꢂ6H2O (2.0 mmol, 0.47 g) was added with
constant stirring. The solid which precipitated was washed several
X-ray crystallography
Details of the crystal data, data collection and refinement
parameters for 1 and 2 are summarized in Table 1. Intensity data

P. Valarmathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 285–292
287
Table 2
were collected at ambient temperature (293(2) K) on Oxford dif-
fraction ‘Xcalibur, Sapphire3’ using graphite monochromated Mo
radiation ( = 0.71073 Å). The structures of 1 and 2 were solved
Selected bond lengths (Å) and bond angles (°) of 1 and 2.
Ka
c
1
2
by SIR-92 [24] and SHELXS-97 [25] respectively and refined by full
matrix least square with SHELXL-97 [24]. All the non-hydrogen
atoms were refined anisotropically and hydrogen atoms were re-
fined isotropically. Selected bond distances and angles are given
in Table 2.
Bond lengths
NiAN2
NiAS1
NiAP1
NiAS2
S2AC19
S1AC19
S3AC32
C19AN1
N2AC32
1.861(3)
2.1841(8)
2.2135(8)
2.2202(8)
1.702(3)
1.714(3)
1.617(3)
1.322(3)
1.153(4)
S1ANi1
S2ANi1
C13AS1
C13AS2
C13AN1
C7AN1
C8AN1
–
2.1914(14)
2.2073(13)
1.710(4)
1.726(4)
1.303(5)
1.483(6)
1.471(6)
–
3. Results and discussion
–
–
3.1. Infrared spectral studies
Bond angles
N2ANiAS1
N2ANiAP1
S1ANiAP1
N2ANiAS2
S1ANiAS2
P1ANiAS2
S2AC19AS1
171.02(8)
95.39(8)
92.70(3)
93.21(8)
78.51(3)
170.79(3)
109.31(16)
S1ANi1AS1i
S1ANi1AS2i
S1ANi1AS2
S2ANi1AS2i
C13AS1ANi1
C13AS2ANi1
S1AC13AS2
180.00(6)
100.75(4)
79.25(4)
180
86.04(15)
85.17(15)
109.5(2)
As concerns the dithiocarbamate moiety, two main regions of
the IR are of interest: first the 1450–1580 cmꢁ1 region, which is
primarily associated with the ‘‘thioureide’’ band due to the
v(NACS2) vibration; second, the 940–1060 cmꢁ1 region which is
associated with the v(CAS) vibrations. Dithiocarbamate com-
pounds exhibit a characteristic band at around 1500 cmꢁ1 assign-
able to v(NACS2), this band defines a carbonAnitrogen bond
order between a single bond (1250–1350 cmꢁ1) and a double bond
(1640–1690 cmꢁ1) [26] (Scheme 2 [27,28]). IR spectra of the com-
plexes 1 and 2 show v(NACS2) bands at 1514 and 1499 cmꢁ1
,
R
R
S
R
R
R
R
S
S
C
R
S
S
N
C
N
N
C
respectively, indicating the partial double bond character. The
mesomeric drift of electrons from the dithiocarbamate moiety to-
wards the metal increases the contribution of the canonical form
(c). This is reflected in the shift in v(NACS2) value of 1 to higher
wavenumber when compared with that observed in 2. The
v(CAS) bands appear around 1000 cmꢁ1 without any splitting, sup-
porting the bidentate coordination of the dithiocarbamte moiety
[29]. The observed stretching frequency at 2094 cmꢁ1 for complex
1 is attributed to the ‘N’ coordinated thiocyanate anion.
=
N
C
S
S
S
R
(a)
(b)
(c)
Scheme 2. Resonance structures of dithiocarbamate (NCS2) moiety.
at 390 nm is assigned to the charge transfer transition. This band
is also observed in the spectra of square planar nickel(II) in the
dithiocarbamate complexes. The bands below 350 nm are con-
nected with intraligand transitions in the S2CNꢁ group [31].
Electronic spectral studies
The observed band at 485 nm for complex 1 can be attributed to
the d–d electron transitions for nickel(II) complexes that contain
the NiS2PN chromophore [30]. The electronic spectrum of 2 shows
two bands (489 and 642 nm) that are typical for square planar
Ni(dtc)2 complexes and are assigned to d–d transition. The band
NMR spectral studies
NMR spectra were recorded using TMS as internal reference.
CDCl3 was used as solvent. The 13C NMR spectra were recorded
in the proton decoupled mode.
Table 1
Crystal data, data collection and refinement parameters for 1 and 2.
1
2
Empirical formula
FW
C
32H27N2NiOPS3
C26H24N2NiO2S4
583.42
641.45
Crystal dimensions (mm)
0.30 ꢃ 0.25 ꢃ 0.20
Triclinic
P–1
0.22 ꢃ 0.20 ꢃ 0.20
Monoclinic
C2/c
Crystal system
Space group
a (Å)
b (Å)
c (Å)
10.1501(6)
12.2115(6)
13.7059(9)
96.070(4)
105.169(5)
109.093(4)
1514.95(15)
2
16.095(5)
9.431(5)
18.248(5)
90.000(5)
107.018(5)
90.000(5)
2648.6(18)
4
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dc (g cmꢁ3
)
1.406
0.928
1.463
1.075
l
(cmꢁ1
)
F(000)
(Å)
h Range (°)
664
Mo K
3.12–32.26
1208
Mo Ka (0.71073)
3.17–32.51
c
a
(0.71073)
Index ranges
ꢁ14 6 h 6 12, ꢁ13 6 k 6 18, ꢁ20 6 l 6 19
ꢁ23 6 h 6 21, ꢁ13 6 k 6 14, ꢁ26 6 l 6 26
Reflections collected
Observed reflections [I > 2
Weighting scheme
16795
9176
4189
r
(I)] 9660
Calc. W = 1/(
r
2(F2o) + (0.1000p)2 + 0.8337p) where p = (Fo2 + 2F2c)/3 Calc. W = 1/(
r
2(Fo2) + (0.0931p)2 + 0.0000p) where p = (Fo2 + 2F2c)/3
Number of parameters refined 363
172
0.0793, 0.2008
0.953
R[F2 > 2
r
(F2)], wR(F2)
0.0548, 0.1178
0.817
GOOF

288
P. Valarmathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 285–292
Fig. 1. Variable temperature 1H NMR spectra of 1 at (a) room temperature, (b) 35 °C (c) 45 °C and (d) 55 °C.
1H, 13C and 31P NMR spectral studies
with an upfield shift of about 3.4 ppm compared with that found in
2 (206.0 ppm). The observed shielding in 1 indicates the effect of
PPh3 on the mesomeric drift of electron density toward nickel
through the thioureide CAN bond. There is a strong empirical
1H NMR and 13C NMR analysis of the 1 and 2 show good agree-
ment with other data to characteristize the structures of the com-
plexes. The N13CS2 carbon signal for the 1 is observed at 209.4 ppm

P. Valarmathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 285–292
289
Fig. 2. Variable temperature 13C NMR spectra of 1 at (a) room temperature, and (b) 55 °C.
correlation between d (N13CS2) values and the carbonAnitrogen
stretching vibration in the infrared spectra: the higher v(NACS2)
values indicate an increased carbonAnitrogen double bond charac-
ter, which well correlates with lower d (N13CS2) values because of a
greater electron density on the NCS2 moiety. In a semi empirical
way, d (N13CS2) could be expressed as a linear function of the
complex 1 compared to the free PPh3 signal observed at ꢁ5 ppm
[33]. A very high deshielding of signal observed for 1 is attributed
to the movement of electron density from the phosphorus towards
the nickel atom on complexation.
Variable temperature 1H NMR spectral studies on 1
sum of CN, CS1 and CS2
p
-bond orders, and v(NACS2) as a linear
-bond
-bonds and to decrease
-bonds. Therefore, the
Variable temperature 1H NMR spectra of [Ni(bfdtc)(NCS)(PPh3)]
are given in Fig. 1. In the case of [Ni(bfdtc)(NCS)(PPh3)], two sing-
lets are expected for methylene protons of benzyl and furfuryl
groups of bfdtc in the aliphatic region. But at room temperature
(21.9 °C) four lines are observed in the region 4.44–4.76 ppm,
while when the temperature is increased, the spectral lines merged
and at 55 °C two spectral lines (broad doublet) are observed. The
fast isothiocyanate ligand exchange appears to be responsible for
function of the CAN -bond order [32]. The sum of the
p
p
order is derived to be maximal for equal
with increasing in equality of the three
p
p
compounds with high NACS2 values have low CS and low total
p
-bond order, thus leading to low d (N13CS2) values and vice versa.
31P chemical shift is observed at 22.2 ppm for complex 1. A good
extent of deshielding of 27 ppm is observed for the 31P signal of

290
P. Valarmathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 285–292
51.5 ppm (51.7 and 51.2 ppm), while when the temperature is
(a)
increased to 55 °C, the doublet merged and only two signals are
observed. The fast isothiocyanate ligand exchange appears to be
responsible for this process.
When ethanol was added to
a chloroform solution of
[Ni(bfdtc)(NCS)(PPh3)], the purple-red colour changed immedi-
ately to greenish yellow. After the mixture stood overnight, a deep
green precipitate formed. The precipitate was identified as
[Ni(bfdtc)2] by comparing its melting point with those of authentic
sample. As expected for a ligand dissociation process, the com-
pounds were sensitive to the nature of the solvents present.
(b)
Cyclic voltammetric studies
Both compounds are found to undergo
a single electron
0
-0.4
-0.8
-1.2
E (Volt)
-1.6
-2.0
reduction process in the potential range 0 to ꢁ1.6 V. Cyclic voltam-
mograms are given in Fig. 3. The reductions are irreversible. The
reduction potentials for 1 and 2 are observed at ꢁ931 and
ꢁ1141 mV, respectively. The lower reduction potential observed
for heteroleptic complex 1 indicates the ease of electron addition
in the heteroleptic complex because of the presence of PPh3 around
the nickel atom [34]. Based on IR and 13C NMR spectral studies,
CAN thioureide in 1 has maximum double bond character and
hence, complex 1 is expected to be more difficult to reduce; in real-
ity, however, complex 1 is more easily reduced than the parent
Fig. 3. Cyclic voltammograms of (a) 1 and (b) 2.
this process. The aromatic protons are not discussed because of
their complicated multiplets.
Similar ligand exchange was reported for [Ni(S2CNR2)(PPh3)X]
(R = Et and X = Cl, I, SCN) complexes [21]. In these complexes, at
ꢁ60 °C two different R resonances are observed. But at room tem-
perature one R resonance is observed. In this complex, the fast
ligand (X) exchange process occurs only at low temperature
(ꢁ60 °C). But in the case of 1, the fast isothiocyanate ligand ex-
change process occurs at room temperature. This indicates that
the N-bound organic moiety in dithiocarbamate ligand affects the
properties of the complex.
complex 2, probably because of the extensive p-back bonding with
phosphorus atom which drains the excess negative charge on the
metal and hence lowers the reduction potential.
Structural analysis
The ORTEP diagram of the 1 is shown in Fig. 4. Complex 1 is
monomeric and discrete. In this complex, nickel cation is
coordinated by two sulfur atom from N-benzyl-N-furfuryl dithio-
carbamate, one nitrogen atom from the thiocyanate and one
phosphorus atom from PPh3 into a distorted square planar config-
uration. The angles S1ANiAP1 [92.70(3)°]; N2ANiAP1 [95.39(8)°]
and N2AN1AS2 [93.21(8)°] are less distorted from the 90° than
the angle S1ANiAS2 [78.51(3)°]. The S1ANiAS2 angle is smaller
Variable temperature 13C NMR spectral studies on
[Ni(bfdtc)(NCS)(PPh3)]
13C NMR spectra of [Ni(bfdtc)(NCS)(PPh3)] at room temperature
and 55 °C are shown in Fig. 2. In the case of [Ni(bfdtc)(NCS)(PPh3)],
two signals are expected for methylene carbons of benzyl and
furfuryl groups of bfdtc. But at room temperature (21.9 °C) two
pseudo doublets are observed at 43.4 (43.6 and 43.2 ppm) and
Fig. 4. ORTEP diagram of 1.

P. Valarmathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 285–292
291
Fig. 5. ORTEP diagram of 2.
than 90° due to the chelation of the N-benzyl-N-furfuryldithiocar-
bamate. The NiAS bonds in [Ni(bfdtc)(NCS)(PPh3)] are asymmetric.
The asymmetry has been explained based on the differences in the
dithiocarbamate complexes, which confirms the considerable
double bond character associated with CAS bonds. The short thio-
ureide CAN distances, 1.322(3) and 1.303(5) Å of 1 and 2, respec-
trans influence exerted by PPh3 and NCSꢁ. PPh3, being a good
p
tively, indicate the p electron density delocalized over the S2CN
acceptor has a greater trans influence and hence the NiAS bonds
moiety and this thioureide bond has a significant double bond
trans to PPh3 is longer than the other NiAS bond.
character.
A short NiAP distance [2.2135(8) Å], shows a better bonding
and back bonding interaction between Ni and P in the complex.
The other parameters of the phenyl rings are normal and observed
average PAC distance is 1.815(3) Å. The CAPAC angles deviate
appreciably from the tetrahedral angle and the crowding of the
phenyl ring causes the PACAC angles to be asymmetric. The NiAN
distance [1.816(3) Å] is siginificantly shorter than the distance re-
ported for the octahedral [Ni(en)2(NCS)2] (2.15 Å) [35] which
shows the effective bonding between the nickel atom and NCSꢁ.
In the isothiocynate part, the NACAS bond angle is almost linear
[NACAS = 178.1(3)°]. The CAN bond distance in thiocyanate is
[1.153(4) Å] which is shorter than that of thioureide NAC bond dis-
tance of 1.322(3) Å. The CAS bond length in the thiocyanate group
is 1.617(3) Å, which is similar to the C@S distance of 1.69 Å.
The ORTEP diagram of 2 is shown in Fig. 5. Complex 2 is
monomeric with eight molecules per unit cell. The Ni(II) cation is
coordinated with the four sulfur atoms of the two N-benzyl-N-fur-
furyldithiocarbamate ligands. The nickel lies on an inversion centre
with a distorted square planar environment of the NiS4 chromo-
phore. Because of the small bite angles associated with the dithio-
carbamate moiety [SANiAS = 79.25(4)°], the NiS4 chromophore is
not perfectly square planar arrangement. The torsion angles,
S1AC13AN1AC89 [–174.9(3)°]; S2AC13AN1AC8 [5.3(6)°];
S1AC13AN1AC7 [2.8(6)°]; S2AC13AN1AC7 [–177.1(3)°] confirm
the near planarity of the S2CN moiety. The near equality of the
two NiAS distances confirms the isobidendate coordination of
the dithiocarabamate group. The crystal structure of a triclinic
polymorph of complex 2 has been reported recently [23].
Conclusions
The crystalline compounds 1 and 2 were prepared and their
structures and properties were characterized by cyclic voltamme-
try, IR, electronic, 1H and 13C NMR spectroscopy. The Ni(II) ion in
complex 1 is four coordinated with two sulfur, one phosphorus
and one nitrogen atoms and giving to a distorted square planar
arrangement. Variable temperature 1H and 13C NMR spectral stud-
ies show that the ligand exchange process occurs at room temper-
ature in 1. This supports that N-bound organic moieties (R1 and R2)
in dithiocarbamate ligand (R1R2NCSꢁ2 ) influence the properties of
the complexes.
Appendix A
Crystallographic data have been deposited with the Cambridge
Crystallographic Centre as supplementary publication number
CCDC–962918 and 962942 for 1 and 2, respectively. Copies of
the data can be obtained free of charge an application to CCDC,
12 Union Road, Cambridge CBZ 1FZ, UK.
References
[1] H. Kodamatani, A. Matsuyama, K. Saito, Y. Kono, R. Kanzaki, T. Tomiyasu, Anal.
Sci. 28 (2012) 959–965.
[2] R.L. Paul, J. Radioanal. Nucl. Chem. 297 (2013) 365–370.
[3] A.H. Henckens, K. Colladet, S. Fourier, J.J. Clei, L. Lutsen, J. Gelan, D.
Vanderzande, Macromolecules 38 (2005) 19–26.
In complexes 1 and 2, the dithiocarbamate ligands are biden-
tate, giving four membered chelate rings [NiS2C]. Their planar
geometry is supported by the corresponding torsion angles which
are close to 0 or 180°. The CAS bonds observed in 1 [1.708(3) Å]
and 2 [1.718(4) Å] are similar to those observed in the other
[4] P.C. Gtzsche, Lancet 332 (1988) 1024.
[5] G.D. Thorn, R.A. Ludwig, The Dithiocabamates and Related Compounds,
Elsevier, Amsterdam, 1962. 298 pp.
[6] V.A. Fitsanakis, V. Amarnath, J.T. Moore, K.S. Montine, J. Zhang, T.J. Montine,
Free Radical Biol. Med. 33 (2002) 1714–1723.
[7] F.X. O’shea, Adv. Chem. 85 (1968) 126–139.

292
P. Valarmathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 285–292
[8] N. Srinivasan, S. Thirumaran, S. Ciattini, Spectrochim. Acta A 102 (2013) 263–
[22] P.J. Rani, S. Thirumaran, Eur. J. Med. Chem. 62 (2013) 139–147.
[23] G. Rajpur, V. Singh, A.N. Gupta, M.K. Yadav, V. Kumar, S.K. Singh, A. Prasad,
M.G.B. Drew, N. singh, CrystEngComm. 15 (2013) 4676–4683.
[24] G.M. Sheldrick, Acta Crystallogr. 64A (2008) 112.
[25] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M.C. Burla, G. polidori,
M. Camalli, J. Appl. Cryst. 27 (1994) 435–436.
268.
[9] N. Srinivasan, S. Thirumaran, Superlattices Microstruct. 51 (2012) 912–920.
[10] J. Cookson, P.D. Beer, Dalton Trans. (2007) 1459–1472.
[11] O.D. Fox, M.G.B. Drew, E.J.S. Wilkinson, P.D. Beer, Chem. Commun. (2000) 391–
392.
[12] W.W.H. Wong, D. Curiel, S.-W. Lai, M.G.B. Drew, P.D. Beer, Dalton Trans. (2005)
774–781.
[26] A.W. Herluiger, S.N. Weihold, T.V. Lang, J. Am. Chem. Soc. 92 (1970) 6474–
6481.
[13] P.D. Beer, N. Berry, M.G.B. Drew, O.D. Fox, M.E. Padilla-Tosta, Chem. Commun.
(2001) 199–200.
[14] G. Hogarth, Prog. Inorg. Chem. 53 (2005) 71–561.
[15] N. Srinivasan, P. Valarmathi, S. Thirumaran, S. Ciattini, Trans. Met. Chem. 35
(2010) 815–819.
[16] Z. Travnicek, R. Pastorek, V. Slovak, Polyhedron 27 (2008) 411–419.
[17] R.G. Cavell, B. Creed, L. Gelmini, D.J. Law, R. Meconald, A.R. Sanger,
Somogyvani, Inorg. Chem. 37 (1998) 757–763.
[27] P.A. Ajibade, D.C. Onwudiwe, J. Coord. Chem. 64 (2011) 2963–2973.
[28] L.Z. Xu, P.S. Zhao, S.S. Zhang, Chin. J. Chem. 19 (2001) 436–440.
[29] F. Bonati, R. Ugo, J. Organomet. Chem. 10 (1967) 257–268.
[30] C.K. Jorgensen, J. Inorg. Nucl. Chem. 24 (1962) 1571–1585.
[31] R. Pastorek, J. Kmenick, Z. Trawnick, J. Husaret, N. Dutty, Polyhedron 18 (1999)
2879–2883.
[32] L. Ronconi, L. Giovagnini, C. Marzano, F. Bettio, R. Graziani, G. Pilloni, D.
Fregona, Inorg. Chem. 44 (2005) 1867–1881.
[18] G.A. Flouds, A.M.A. Bennet, M.L. Niven, D.A. Thornton, K.J. Cavell, S. Desjardius,
E.J. Peacock, J. Mol. Catal. 87 (1994). 1170-136.
[33] R.M. Silverstein, F.X. Webster, Spectrometric Identification of Organic
Compounds, 6th ed., Wiley, New York, 1998.
[19] E.R.T. Tiekink, CrystEngComm. 5 (2003) 101–113.
[20] M.J. Cox, E.R.T. Tiekink, Rev. Inorg. Chem. 17 (1997) 1–23.
[21] J.P. Fackler Jr., J.J.B. Lin, J. Andrews, Inorg. Chem. 16 (1977) 450–457.
[34] K. Ramalingam, G. Aravamudan, M. Seshasayee, Inorg. Chim. Acta 128 (1987)
231–237.
[35] B.W. Brown, E.C. Lingafelter, Acta Crystallogr. 16 (1963) 753–758.