Synthesis and characterization of homoleptic and heteroleptic complexes involving dithiocarbamates, triphenylphosphine, and nickel(II)

Article abstract of DOI:10.1080/10426507.2012.704103

Six new nickel complexes of two dithiocarbamate ligands (cyfdtc = N-cyclohexyl-N- furfuryldithiocarbamate and bztpedtc = N-benzyl-N-[2- thiophenylethyl]dithiocarbamate) namely, (Ni[cyfdtc]2) (1), (Ni[bztpedtc]2) (2), (Ni[cyfdtc][NCS][PPh3]) (3), (Ni[bztpedtc] [NCS][PPh3]) (4), (Ni[cyfdtc][PPh3]2)ClO4 (5), and (Ni[bztpedtc][PPh3]2)ClO4 (6) have been prepared and characterized using IR, electronic, and NMR (¹H and ¹³C) spectra. A single crystal X-ray structural analysis was carried out for complex 3 and showed that nickel is in a distorted square planar arrangement with the NiS2PN chromophore. The shift in νCN of the heteroleptic complexes to higher frequencies compared with the parent complex is assigned to mesomeric delocalization of electron density from the dithiocarbamate ligand toward the metal atom, which increases the contribution of polar thioureide form in mixed ligand complexes. Electronic spectral studies suggest square planar geometry for the complexes. In the ¹³C NMR spectra, the upfield shift of NCS2 carbon signal for 3 and 4 from the chemical shift value of 1 and 2 is due to effect of PPh3 on the mesomeric drift of electron density toward nickel throughout thioureide CN bond.

Full text of DOI:10.1080/10426507.2012.704103

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Phosphorus, Sulfur, and Silicon and the
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Synthesis and Characterization
of Homoleptic and Heteroleptic
Complexes Involving Dithiocarbamates,
Triphenylphosphine, and Nickel(II)
Palanisamy Jamuna Rani a , Subbiah Thirumaran a & Samuele Ciattini
b
a Department of Chemistry , Annamalai University ,
Annamalainagar , Tamil Nadu , India
b Centro di Cristallografia Strutturale , Polo Scientifio di Sesto
Fiorentino , Sesto Fiorentino , Firenze , Italy
Accepted author version posted online: 27 Jun 2012.Published
online: 31 May 2013.
To cite this article: Palanisamy Jamuna Rani , Subbiah Thirumaran & Samuele Ciattini
(2013) Synthesis and Characterization of Homoleptic and Heteroleptic Complexes Involving
Dithiocarbamates, Triphenylphosphine, and Nickel(II), Phosphorus, Sulfur, and Silicon and the Related
Elements, 188:6, 778-789, DOI: 10.1080/10426507.2012.704103
To link to this article: http://dx.doi.org/10.1080/10426507.2012.704103
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Phosphorus, Sulfur, and Silicon, 188:778–789, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2012.704103
SYNTHESIS AND CHARACTERIZATION OF HOMOLEPTIC
AND HETEROLEPTIC COMPLEXES INVOLVING
DITHIOCARBAMATES, TRIPHENYLPHOSPHINE,
AND NICKEL(II)
Palanisamy Jamuna Rani,1 Subbiah Thirumaran,1
and Samuele Ciattini2
1Department of Chemistry, Annamalai University, Annamalainagar, Tamil Nadu,
India
2Centro di Cristallografia Strutturale, Polo Scientifio di Sesto Fiorentino, Sesto
Fiorentino, Firenze, Italy
GRAPHICAL ABSTRACT
Abstract Six new nickel complexes of two dithiocarbamate ligands (cyfdtc = N-cyclohexyl-N-
furfuryldithiocarbamate and bztpedtc = N-benzyl-N-[2-thiophenylethyl]dithiocarbamate)
namely, (Ni[cyfdtc]2) (1), (Ni[bztpedtc]2) (2), (Ni[cyfdtc][NCS][PPh3]) (3), (Ni[bztpedtc]
[NCS][PPh3]) (4), (Ni[cyfdtc][PPh3]2)ClO4 (5), and (Ni[bztpedtc][PPh3]2)ClO4 (6) have
been prepared and characterized using IR, electronic, and NMR (1H and 13C) spectra.
A single crystal X-ray structural analysis was carried out for complex 3 and showed
that nickel is in a distorted square planar arrangement with the NiS2PN chromophore.
The shift in νC
of the heteroleptic complexes to higher frequencies compared with
N
the parent complex is assigned to mesomeric delocalization of electron density from the
Received 7 April 2012; accepted 13 June 2012.
Address correspondence to Subbiah Thirumaran, Department of Chemistry, Annamalai University,
Annamalainagar 608 002, India. E-mail: sthirumaran@yahoo.com
778

HOMOLEPTIC AND HETEROLEPTIC COMPLEXES
779
dithiocarbamate ligand toward the metal atom, which increases the contribution of polar
thioureide form in mixed ligand complexes. Electronic spectral studies suggest square planar
geometry for the complexes. In the 13C NMR spectra, the upfield shift of NCS2 carbon signal
for 3 and 4 from the chemical shift value of 1 and 2 is due to effect of PPh3 on the mesomeric
drift of electron density toward nickel throughout thioureide C N bond.
Keywords Dithiocarbamate; triphenylphosphine; nickel(II); spectral; X-ray structure
INTRODUCTION
The coordination chemistry of complexes containing sulfur donor ligands has been
steadily growing due to their resemblance with biomolecules like amino acids (e.g., methio-
nine, cystein), peptides such as glutathione, proteins, enzymes, and vitamins.1 Among the
various organosulfur systems, dithiocarbamates have special significance due to their wide
applications such as potential pesticides, in analytical determinations, and as fungicides and
vulcanizing agents.2–4 The versatility of dithiocarbamato ligands may be attributed to their
small bite angle, leading to the stabilization of a wide range of oxidation states of transi-
tion metal and main group elements.5,6 The complexing ability of dithiocarbamato ligands
stems from the presence of the potential sulfur donors, which can delocalize positive charge
from the metal toward the periphery of the complex.7 These dithiocarbamato complexes
have been shown to be useful precursors for formation of metal sulfide nanoparticles.8–10
Recently, dithiocarbamates have also been used as structural motifs in the supramolecular
chemistry due to their robust complexing ability.11
The diversity in applications inherent to nickel(II) complexes with homoleptic and
chelating phosphine as catalysts12–14 and in the medicinal field,15 combined with their
structural novelty, has resulted in the synthesis of a series of compounds with NiPnX
(X = halogens or N or C or S) chromophores. Nickel(II) dithiocarbamates with a planar
NiS4 chromophores are found to show interesting variations in reactivity toward soft Lewis
bases such as phosphines and hard bases such as nitrogenous ligands.16,17
The dithiocarbamate complex core M S2CNR2 (M = metal, R = alkyl) could
prove to be of great synthetic utility, since a wide variety of organic substituents can be
incorporated in this stable bidentate system. It gives rise to the chemical “fine tuning” of
the biological properties of the complex by variation of the substituent R in M S2CNR2.18
The aim of the present work was to prepare Ni(II) complexes of two unsymmetrical
dithiocarbamate ligands with furfuryl and 2-thiophenylethyl substituents and the reactivity
of these complexes toward PPh3. In this paper, we report the synthesis and spectral studies
of complexes 1–6 along with the single crystal X-ray structure of 3.
RESULTS AND DISCUSSION
Homoleptic and heteroleptic complexes were prepared according to the synthetic
procedure shown in Schemes 1 and 2. Furfuraldehyde and benzaldehyde were condensed
with cyclohexylamine and thiophenethylamine, respectively, to form the imine. Sodium
borohydride reduction of the imine in methanol–dichloromethane afforded the secondary
amine as yellow oil. The homoleptic [Ni(dtc)2] complexes of 1 and 2 were prepared
from a secondary amine in EtOH by reaction with carbon disulfide and NiCl2 in water.
The reaction under continued reflux (3 h) between [Ni(dtc)2], NiCl2, NH4SCN, and PPh3
yielded [Ni(dtc)(NCS)(PPh3)] (3 and 4). [Ni(dtc)(PPh3)2]ClO4 (5 and 6) complexes were
prepared by refluxing [Ni(dtc)2], NiCl2, NaClO4, and PPh3 in chloroform–methanol (3:2,

780
P. J. RANI ET AL.
Scheme 1 Preparation of complexes 1, 3, and 5.
50 mL) mixture. The complexes are quite stable at ambient conditions. They are soluble
in acetonitrile, chloroform, and dichloromethane and insoluble in water, methanol, and
ethanol.
IR Spectra
The infrared spectra of dithiocarbamato complexes consist of two characteristic
bands, which are of direct structural significance. The first lies in the region 950–1050 cm−1
,
which exhibits the nature of coordination mode (monodentate or bidentate) of the dithio-
carbamate moiety19 while the second lies in between 1450–1600 cm−1 and is termed the
thioureide band.20 This thioureide band may be considered as an intermediate between
single- and double-bonded C N and its position indicates the shift of electron density
toward the coordinating metal ion. Based on Bonati and Ugo21 criterion, the presence of
a solitary band in the 950–1050 cm−1 region is due to the bidentate coordination of the
dithiocarbamato group while the splitting of this band within narrow range of 20 cm−1 is
due to the monodentate nature of the dithiocarbamato group.

HOMOLEPTIC AND HETEROLEPTIC COMPLEXES
781
Scheme 2 Preparation of complexes 2, 4, and 6.
The infrared spectra of 1–6 show νC–N(thioureide) bands in the region 1461–
1502 cm−1, indicating the partial double bond character. In the case of heteroleptic com-
plexes, the νC values were found to be larger than those of the parent dithiocarbamates.
N
This observation shows the increased strength of the thioureide bond due to the presence
of π-accepting phosphine. In the present study, the νC S stretching vibrations are observed
in the region 1011–1025 cm−1 without any splitting, supporting the bidentate coordination
of the dithiocarbamate ligand. The bands observed around 2090 (νC N) and 840 cm−1
(νC S) for the complexes 3 and 4 may imply the assumption that the thiocyanate group
is coordinated to the nickel via the nitroge−n atom.22 The intense signals observed around
1090 cm−1 for 5 and 6 are assigned to ClO4 .
Electronic Spectra
Dithiocarbamates generally show three bands in the UV region. These bands are
ascribed to the intramolecular intraligand transitions corresponding to π→π∗ transitions

782
P. J. RANI ET AL.
of the N C S and S C S groups and n→π∗ transition located on the sulfur atom.23
In the case of 1 and 2, two d–d transition bands are observed around 630 and 487 nm
2
2
2
2
2
corresponding to the dxy → dx –y and dz → dx –y transitions, respectively, supporting
a square-planar structure.24 The d–d transition bands are observed at 487, 487, 480, and
2
2
2
485 nm for complexes 3, 4, 5 and 6, respectively. The bands are assigned to dz /dxy → dx –y
transitions.17
1H NMR Spectra
1H NMR spectra of 2 and 4 are given in Figure 1 to show single broad signal and broad
doublets observed for each methylene proton in 2 and 4, respectively. Free N-cyclohexyl-
N-furfurylamine shows a singlet at 3.78 ppm and a broad signal at 2.42 ppm due to
methylene protons of furfuryl and methine proton of cyclohexyl groups, respectively. In the
complexes 1, 3, and 5, the methylene protons of furfuryl and methine proton of cyclohexyl
Figure 1 1H NMR spectra of (a) 2 and (b) 4.

HOMOLEPTIC AND HETEROLEPTIC COMPLEXES
783
group, adjacent to N-atom, undergo strong deshielding to give the signals around 4.74 and
4.41 ppm, respectively. Similarly, in the case of complexes 2, 4, and 6, the benzyl methylene
protons (4.69 ppm) of benzyl group and methylene protons (3.73 ppm) of thiophenylethyl
group, adjacent to nitrogen atoms, are strongly deshielded on complexation compared
to free N-benzyl-N-(2-thiophenylethyl)amine [3.66 ppm (NCH2(benzyl)) and 2.92 ppm
(NCH2(thiophenylethyl))]. The observed deshielding of methylene and methine protons
adjacent to nitrogen atom is attributed to the release of electrons on the nitrogen of the NR2
groups, forcing high electron density toward the sulfur (or) the metal via the thioureide
π-system. The magnitude of deshielding decreases with an increase in distance from the
metal center or thioureide bond, the other proton signals are also slightly deshielded on
complexation.
In the case of 3, the signals due to furfuryl CH2 protons and cyclohexyl methine
protons appear as broad doublets. Similarly, the methylene protons adjacent to the nitrogen
of bztpedtc in heteroleptic complexes 4 (Figure 1) and 6 are observed as broad doublets.
This is due to the ligand exchange reactions as observed in [Ni(SCNEt2)(PPh3)X] (X = Cl,
Br, I, NCS) complexes.25
13C NMR Spectra
13C NMR spectrum of 3 is given in Figure 2 to show the pseudo doublets observed
for methylene and methine carbons adjacent to nitrogen atom of 3. The most important
13C NMR signals of the S213CN carbons are observed in the region 205.3–208.9 ppm
for [Ni(dtc)2] and [Ni(dtc)(NCS)(PPh3)] with a very weak intensity characteristic of the
quaternary carbon signals. The S213CN carbon signal for 3 and 4 is observed at 205.3 and
205.7 ppm, respectively, with an upfield shift of about 3.5 ppm, respectively, compared
Figure 2 13C NMR spectrum of 3.

784
P. J. RANI ET AL.
with that found in parent 1 (208.8 ppm) and 2 (208.9 ppm). The presence of π-acid
(triphenylphosphine) in [Ni(dtc)(NCS)(PPh3)] increases the mesomeric drift of electron
density from the dithiocarbamate moiety toward the metal atom. This yields an increase in
the Nδ+ ..... δ− partial double bond character, and as a result, displacement of the electron
C
density from the nitrogen atom of the dithiocarbamate group.22 This explains the shielding of
carbon sites in the N C(S)S group of [Ni(dtc)(NCS)(PPh3)]. Most of the dithiocarbamate
signal in the 13C NMR spectra of mixed ligand complexes appeared as pseudo doublets.
This is consistent with the square planar geometry for the complexes. Doublets or pseudo
triplets are also observed in triphenylphosphine transition metal complexes.26
Crystallographic Analysis of Complex 3
Complex 3 is discrete and monomeric. Four formula units are present in the unit cell.
The ORTEP diagram is shown in Figure 3. The structure consists of distorted square planar
metal coordination with NiS2PN chromophore. The structure adopted by this complex is
characterized using τ4-descriptor for four coordination ions suggested by Yang et al.27 The
distortion index is defined as τ4 = 360–(α+β)/141. In this complex, α and β are the two
largest angles (N2 Ni S1 = 171.97◦ and P Ni S2 = 174.97◦). The τ4 values for perfect
tetrahedral, trigonal pyramid, seesaw structure, and perfect square planar are 1.00, 0.85,
0.64–0.07, and 0.00, respectively. The τ4 value of this complex is 0.09, which indicates
that the coordination geometry is a seesaw structure. There are considerable differences
between the pairs of Ni S and S C bonds and it is interesting to note that the longer
Ni S bond [Ni S2 = 2.213(8) Å compared with Ni S1 = 2.1677(8) Å] is associated
with shorter S C distance (S2 C2 = 1.716[3] Å compared with S1 C2 = 1.733[3]
Å). This indicates that the dithiocarbamate ligand is asymmetrically linked to nickel. The
significant asymmetry in Ni S distance is due to the difference in the trans-influencing
properties of PPh3 and NCS−. Ni S bond trans to PPh3 is longer than the other Ni S
bond. This observation supports the more effective trans effect of PPh3 over NCS−. The
asymmetric C S distances are shorter than the typical C S single bond length (1.81 Å) due
to the partial π-delocalization in the NCS2 groups.6 The C N distance (1.303[3] Å), which
clearly indicates the contribution of the thioureide form to the dithiocarbamate ligand. This
contrasts well with the adjacent typical single bond N C distance (1.485[3] Å).
Figure 3 ORTEP diagram of 3.

HOMOLEPTIC AND HETEROLEPTIC COMPLEXES
785
In the isothiocynate part, the N C S is almost linear [N C S = 179.3(3)◦].
. The Ni N distance is 1.856(2) Å, which is similar to that observed in similar
[Ni(dtc)(NCS)(PPh3)] complexes.28 The observed Ni P distance (2.1977[8] Å) is rela-
tively short compared to a long Ni P = 2.40 Å bonded distance reported in the literature.29
The cyclohexyl ring in the dithiocarbamate fragment is in the chair conformation. The
C C and C O bond distances associated with furfuryl ring are normal. The bond lengths
and angles in the phenyl rings are in good agreement within experimental accuracy, with
the values found in the literature.30
CONCLUSIONS
New complexes [Ni(dtc)2], [Ni(dtc)(NCS)(PPh3)], and [Ni(dtc)(PPh3)2]ClO4
(dtc = cyfdtc, bztpedtc) have been synthesized and characterized through elemental
analysis and spectroscopic studies. The spectral studies on complexes 1–6 indicate that
the central metal atom is in a planar environment for all complexes. Single crystal X-ray
analysis of 3 confirmed that the nickel is in a distorted square planar environment with
S2PN chromophore. A significant asymmetry in the Ni S bond in 3 [2.1677(8) and
2.2131(8) Å] supports the less effective trans effect of NCS over PPh3.
EXPERIMENTAL
All reagents and solvents were commercially available high-grade materials
(Merck/sd Fine/Himedia) and used as received. IR spectra were recorded on a Thermo
NICOLET AVATAR 330 FT-IR spectrophotometer (range 400–4,000 cm−1) as KBr
pellets. A Shimadzu UV-1650 PC double beam UV-visible spectrophotometer was used
for recording the electronic spectra. The spectra were recorded in CHCl3 and the pure
solvent was used as the reference. The NMR spectra were recorded on a Bruker 500 MHz
NMR spectrometer at room temperature (r.t.) in CDCl3, using TMS as internal reference.
X-Ray Crystallography
Diffraction data for 3 were recorded on an Xcalibur-3/CCD diffractometer using
graphite-monochromated MoKα radiation (λ = 0.71069 Å) at an ambient temperature.
The structure was solved by SHELXS31 and refined by full-matrix least-squares methods
in SHELXL.31 All the nonhydrogen atoms were refined anisotropically and the hydrogen
atoms were refined isotropically. Details of the crystal data and structure refinement param-
eters for 3 are summarized in Table 1. Selected bond distances and angles are presented in
Table 2.
Preparation of Amine
N-Cyclohexyl-N-furfurylamine and N-benzyl-N-(2-thiophenylethyl)amine were pre-
pared by general methods reported earlier.32
Preparation of Complex 1
N-Cyclohexyl-N-furfurylamine (0.7 mL, 4 mmol) and carbon disulfide (0.3 mL,
4 mmol) were dissolved in ethanol (20 mL) and stirred for 30 min. NiCl2·6H2O (0.57 g,

786
P. J. RANI ET AL.
Table 1 Crystal structure and data refinement parameters for 3
Empirical formula
FW
C31H31N2OPS3Ni
633.44
Crystal dimensions (mm)
Crystal system / Space group
0.2 × 0.2 × 0.2
Monoclinic/P21/c
8.9130(10)
20.0970(10)
17.3590(10)
90.000(5)
98.193(5)
90.00
3077.7(4)
4
a (Å)
b (Å)
c (Å)
α (◦)
β (◦)
γ (◦)
V (Å3)
Z
Dc (g cm−3
μ (cm−1
)
1.367
0.913
)
Crystal size (mm)
Colour/shape
Temp. (K)
0.2 × 0.2 × 0.2
Dark red/Prism
293(2)
Theta range for collection
Reflections collected
Independent reflections
Data/restrains/parameters
Goodness of fit on F2
Final R indices (I > 2σ[I])
R indices (all data)
4.45–26.40
15216
6077
4011/0/352
1.041
R1 = 0.0439, wR2 = 0.0929
R2 = 0.0773, wR2 = 0.1000
0.436–0.387
Largest difference peak/hole (eÅ−3
)
2 mmol) was dissolved in 10 mL of water and added to the solution with constant stirring.
A green powder precipitated that was filtered and dried.
◦
Yield: 70%. mp 300 C. IR (KBr, cm−1) 1461 (νC N), 1011 (νC S), 2937, 2854
(νC H(aliph.)). UV-Vis (CHCl3, λmax/nm (ε/L mol−1 cm−1)): 622 (115), 481 (190), 371
(7350), 235 (35700). 1H NMR (ppm): δ = 1.09 (b, 2H, H–4 (ax)), 1.30–1.43 (m, 8H, H–3),
1.64 (d, J = 17 Hz, 2H, H–4 (eq)), 1.78 (b, 8H, H–2), 4.44 (b, 2H, H–1), 4.74 (s, 4H,
NCH2 (furfuryl)), 6.33 (b, 2H, H–4 (furyl)), 6.40 (b, 2H, H–3 (furyl)), 7.34 (b, 2H, H–5
(furyl)). 13C NMR (ppm): δ = 25.2 (C–4), 25.6 (C–3), 30.0 (C–2), 41.4 (NCH2 (furfuryl)),
59.2 (C–1), 110.0, 110.8, 141.8, 148.7 (Aryl–C (furyl)), 208.8 (SCS). Anal. Calcd. for
C24H32S4N2O2Ni (%): C, 50.79; H, 5.68; N, 4.93. Found (%): C, 50.45; H, 5.52; N, 4.80.
Table 2 Selected bond distances (Å) and angles (◦) for 3
Bond distances (Å)
Ni N2
Bond angles (◦)
1.856(2)
2.1977(8)
2.1677(8)
2.2131(8)
1.733(3)
1.716(3)
1.607(3)
1.343(3)
N2 Ni S1
171.97(8)
91.91(8)
96.04(3)
93.09(8)
78.95(3)
174.97(3)
125.4(2)
126.8(2)
Ni
P
N2 Ni
S1 Ni
P
P
Ni S1
Ni S2
S1 C2
S2 C2
S3 C3
N2 C3
N2 Ni S2
S1 Ni S2
P
Ni S2
Ni C2 S1
Ni C2 S2

HOMOLEPTIC AND HETEROLEPTIC COMPLEXES
787
Preparation of Complex 2
The same procedure was used as earlier except that N-benzyl-N-(2-
thiophenylethyl)amine was used instead of N-cyclohexyl-N-furfurylamine.
◦
Yield: 75%. mp 210 C. IR (KBr, cm−1) 1501 (νC N), 1021 (νC S), 2923, 2853
(νC H(aliph.)), 3020 (νC H(arom.)). UV-Vis (CHCl3, λmax/nm (ε/L mol−1 cm−1)): 630 (153),
1
487 (401), 398 (1980). H NMR (ppm): δ = 3.13 (b, 4H, N CH2 CH2 C4H3S), 3.72
(b, 4H, NCH2 CH2 C4H3S), 4.65 (b, 4H, NCH2 (benzyl)), 6.83–7.36 (Aryl H). 13C
NMR (ppm): δ = 27.4 (NCH2 CH2 C4H3S), 50.2 (N CH2 CH2 C4H3S), 52.8 (NCH2
(benzyl)), 124.4–139.6 (Aryl C), 208.9 (SCS). Anal. Calcd. for C28H28S6N2Ni (%): C,
52.25; H, 4.38; N, 4.35. Found (%): C, 51.78; H, 4.29; N, 4.31.
Preparation of Complex 3
A mixture of complex 1 (0.56 g, 1.0 mmol), PPh3 (0.52 g, 2 mmol), NiCl2·6H2O
(0.327 g, 1.0 mmol), and NH4NCS (0.152 g, 2.0 mmol) was refluxed for 3 h in
chloroform–methanol solvent mixture (3:2, 50 mL). The purple red solution obtained was
filtered and left for evaporation. After 2 days, a purple red solid separated out, which was
recrystallized from chloroform. Suitable single crystals for X-ray structure analysis were
obtained by repeated crystallization from dichloromethane—methanol solvent mixture.
◦
Yield: 65%. mp 240 C. IR (KBr, cm−1) 1485 (νC N), 1011 (νC S), 2089 (NCS),
2931, 2857 (νC H(aliph.)), 3053 (νC H(arom.)). UV-Vis (CHCl3, λmax/nm (ε/L mol−1 cm−1)):
1
487 (5640), 336 (98600), 240 (362000). H NMR (ppm): δ = 1.06 (b, 1H, H–4 (ax)),
1.35–1.43 (m, 4H, H–3), 1.61 (b, 1H, H–4 (eq)), 1.74 (b, 4H, H–2), 3.98, 4.35 (b, 1H,
H–1), 4.52, 4.73 (b, 2H, NCH2 (furfuryl)), 6.12, 6.29 (b, 1H, H–4 (furyl)), 6.35, 6.42 (b,
1H, H–3 (furyl)), 7.32, 7.34 (b, 1H, H–5 (furyl)), 7.46–7.73 (protons of PPh3). 13C NMR
(ppm): δ = 25.0 (C–4), 25.4 (C–3), 29.9 (C–2), 41.5, 41.8 (NCH2 (furfuryl)), 59.8 (C–1),
110.4, 110.9, 142.2, 147.7 (Aryl C (furyl)), 128.1–134.2 (Aryl C (PPh3)), 205.3 (SCS).
31P NMR (ppm): δ = 29.2. Anal. Calcd. for C31H31N2S3PONi (%): C, 58.78; H, 4.93; N,
4.42. Found (%): C, 58.49; H, 4.84, N, 4.34.
Preparation of Complex 4
The same procedure was used as earlier except that complex 2 was used instead of
complex 1.
◦
Yield: 71%. mp 180 C. IR (KBr, cm−1) 1517 (νC N), 1024 (νC S), 2091 (NCS),
2926, 2866 (νC H(aliph.)), 3074 (νC H(arom.)). UV-Vis (CHCl3, λmax/nm (ε/L mol−1
1
cm−1)): 487 (604), 331 (45900), 250 (69100). H NMR (ppm): δ = 2.98, 3.14 (b, 2H,
NCH2 CH2 C4H3S), 3.56, 3.73 (b, 2H, NCH2 CH2 C4H3S), 4.47, 4.69 (b, 2H, NCH2
(benzyl)), 6.65–7.78 (Aryl H). 13C NMR (ppm): δ = 27.4 (NCH2 CH2 C4H3S), 50.1
(NCH2 CH2 C4H3S), 52.9 (NCH2 (benzyl)), 124.6–139.0 (Aryl C), 205.7 (SCS).
31P NMR (ppm): δ = 20.2, 29.4. Anal. Calcd. for C33H29N2S4PNi (%): C, 61.58; H, 4.55;
N, 1.44. Found (%): C, 60.80; H, 4.39; N, 1.40.
Preparation of Complex 5
A mixture of complex 1 (0.56 g, 1.0 mmol), NiCl2·6H2O (0.237 g, 1.0 mmol),
PPh3 (1.048 g, 4.0 mmol), and NaClO4 (0.242 g, 1.0 mmol) was refluxed for 3 h in

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P. J. RANI ET AL.
chloroform–methanol solvent mixture (3.2, 50 mL). The purple red solution obtained was
filtered and left for evaporation. After 2 days, a purple red solid separated out, which was
recrystallized from chloroform.
◦
Yield: 60%. mp 210 C. IR (KBr, cm−1) 1479 (νC N), 1021 (νC S), 1088 (ClO4),
2923, 2852 (νC H(aliph.)), 3057 (νC H(arom.)). UV-Vis (CHCl3, λmax/nm (ε/L mol−1 cm−1)):
1
480 (135), 322 (5920), 239 (33100). H NMR (ppm): δ = 1.04–1.12 (m, 1H, H–4 (ax)),
1.46 (q, J = 11.6 Hz, 4H, H–3), 1.69 (bd, 1H, H–4 (eq)), 1.78 (bd, 4H, H–2), 4.08 (b,
1H, H–1), 4.67 (s, 2H, NCH2 (furfuryl)), 6.11 (b, 1H, H–4 (furyl)), 6.32 (b, 1H, H–3
(furyl)), 7.14–7.76 (protons of PPh3), 7.33 (b, 1H, H–5 (furyl)). 13C NMR (ppm): δ = 24.8
(C–4), 25.3 (C–3), 29.8 (C–2), 42.2 (NCH2 (furfuryl)), 60.4 (C–1), 110.9, 111.4, 142.6,
147.2 (Aryl C (furyl)), 128.6–134.0 (Aryl C (PPh3)). 31P NMR (ppm): δ = 29.4, 31.2.
Anal. Calcd. for C48H46S2P2O5NClNi (%): C, 61.52; H, 4.95; N, 1.49. Found (%): C,
61.26; H, 4.87; N, 1.47.
Preparation of Complex 6
The same procedure was used as above except that complex 2 was used instead of
complex 1.
◦
Yield: 66%. mp 170 C. IR (KBr, cm-1) 1502 (νC N), 1024 (νC S), 1090 (ClO4),
2921, 2849 (νC H(aliph.)), 3055 (νC H(arom.)). UV-Vis (CHCl3, λmax/nm (ε/L mol−1
1
cm−1)): 485 (206), 324 (22000), 235 (3550). H NMR (ppm): δ = 2.99, 3.13 (b, 2H,
NCH2 CH2 C4H3S), 3.46, 3.72 (b, 2H, NCH2 CH2 C4H3S), 4.64 (s, 2H, NCH2
(benzyl)), 6.70–7.69 (Aryl H). 13C NMR (ppm): δ = 27.5 (NCH2 CH2 C4H3S), 50.2,
50.5 (NCH2 CH2 C4H3S), 52.9 (NCH2 (benzyl)), 124.4–139.6 (Aryl C). 31P NMR
(ppm): δ = 29.2, 30.9, 31.4, 43.4. Anal. Calcd. for C50H44O4S3P2NClNi (%): C, 61.58; H,
4.55; N, 1.44. Found (%): C, 60.80; H, 4.39; N, 1.40.
Supplementary Data
Crystallographic data (excluding structure factors) have been deposited with the Cam-
bridge Crystallographic Data Centre as the supplementary publication no. CCDC 873101.
Copies of the data can be obtained, free charge, on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (Tel.: +44 (0) 1223 762911; E-mail: kamila@ccdc.cam.ac.uk).
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