Effect of diverse solvents on the composition and structure of mixed-ligand nickel(II) dithiocarbamates:NiX(ndtc)(PPh3)

Article abstract of DOI:10.1016/j.poly.2013.11.041

A series of square-planar nickel(II) benzylpiperazine-dithiocarbamato (bpdtc; 1-4) and thiomorpholine-dithiocarbamato (tmdtc; 5-8) complexes of the composition [NiX(ndtc)(PPh₃)] (X symbolizes Cl for 1 and 5, Br for 2 and 6, I for 3 and 7, or NCS for 4 and 8) was prepared and thoroughly characterized by elemental analysis, UV-Vis, IR and NMR spectroscopy, mass spectrometry, molar conductivity and magnetochemical measurements, and by single-crystal X-ray analysis (for complex 1). The solution behaviour study of selected representatives (1, 4, 5 and 8) in various solvents (acetone, acetonitrile, methanol (MeOH), N,N′-dimethylformamide (DMF), chloroform, nitromethane, dimethyl sulfoxide (DMSO), MeOH/water mixture (1:1 v/v)) by a combination of NMR and UV-Vis spectroscopy, mass spectrometry and single-crystal X-ray analysis showed that the complexes decompose back to the synthetic precursors, involving the [Ni(ndtc)₂] species, in DMF and DMSO, while they dissolve without a change in their composition in the remaining solvents.

Full text of DOI:10.1016/j.poly.2013.11.041

Polyhedron 69 (2014) 174–180
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Effect of diverse solvents on the composition and structure
of mixed-ligand nickel(II) dithiocarbamates: [NiX(ndtc)(PPh3)]
a
b
b
b,
⇑
ˇ
ˇ
Richard Pastorek , Pavel Štarha , Bohuslav Drahoš , Zdenek Trávnícek
a Department of Inorganic Chemistry, Faculty of Science, Palacky´ University, 17, listopadu 12, CZ-771 46 Olomouc, Czech Republic
b Regional Centre of Advanced Technologies and Materials, Department of Inorganic Chemistry, Faculty of Science, Palacky´ University, 17. listopadu 12, CZ-771 46 Olomouc,
Czech Republic
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of square-planar nickel(II) benzylpiperazine–dithiocarbamato (bpdtc; 1–4) and thiomorpholine–
dithiocarbamato (tmdtc; 5–8) complexes of the composition [NiX(ndtc)(PPh3)] (X symbolizes Cl for 1 and
5, Br for 2 and 6, I for 3 and 7, or NCS for 4 and 8) was prepared and thoroughly characterized by elemen-
tal analysis, UV–Vis, IR and NMR spectroscopy, mass spectrometry, molar conductivity and magneto-
chemical measurements, and by single-crystal X-ray analysis (for complex 1). The solution behaviour
study of selected representatives (1, 4, 5 and 8) in various solvents (acetone, acetonitrile, methanol
(MeOH), N,N0-dimethylformamide (DMF), chloroform, nitromethane, dimethyl sulfoxide (DMSO),
MeOH/water mixture (1:1 v/v)) by a combination of NMR and UV–Vis spectroscopy, mass spectrometry
and single-crystal X-ray analysis showed that the complexes decompose back to the synthetic precursors,
involving the [Ni(ndtc)2] species, in DMF and DMSO, while they dissolve without a change in their com-
position in the remaining solvents.
Received 3 September 2013
Accepted 30 November 2013
Available online 12 December 2013
Keywords:
Nickel(II) complexes
Dithiocarbamate
Crystal structure
Solution study
NMR
Mass spectrometry
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
This work reports solid-state and solutions studies on a series of
nickel(II) benzylpiperazine– and thiomorpholine–dithiocarbamato
S-donor ligands bearing the dithiocarbamate moiety are com-
monly used for the preparation of transition metal complexes hav-
ing various compositions, geometries, properties and applications.
For example, complexes involving this type of ligand were reported
in the literature as having interesting electrochemical [1], antibac-
terial (higher than tetracycline), antifungal (higher than nystatin)
[2] and antitumor activities (higher in vitro and in vivo activities
as compared with cisplatin) [3] or they may act as precursors for
the preparation of NiS nanoparticles [4]. On the other hand, the
dithiocarbamates presented in this work, i.e. benzylpiperazine–
dithiocarbamate (bpdtc) and thiomorpholine–dithiocarbamate
(tmdtc), are quite rare, since the literature sources contain only
11 transition metal complexes with bpdtc and 41 with tmdtc (Sci-
FinderÒ, 2013). As for the nickel(II) complexes with the above-
mentioned dithiocarbamates, [Ni(bpdtc)2] [5], [Ni(bpdtc)(phen)2]-
ClO4ꢀCHCl3, [Ni(bpdtc)(phen)2]SCN [6], [Ni(tmdtc)2] [7] and
[Ni(en)3(tmdtc)2] [8] have been reported to date. Regarding the
X-ray structures determined for transition metal complexes with
the bpdtc and tmdtc ligands, only three, i.e. [Ni(bpdtc)(phen)2]ClO4-
ꢀCHCl3 [6], [MoO2(tmdtc)2] [9] and [Ni(bpdtc)(PPh3)2]ClO4ꢀPPh3
[10], have been deposited with the Cambridge Structural Database
(CSD ver. 5.34, May 2013 update [11]).
complexes of the type [NiX(ndtc)(PPh3)], whose coordination
sphere consists of a bidentate-coordinated S-donor dithiocarba-
mate anion, one PPh3 molecule and one of the Clꢁ, Brꢁ, Iꢁ or NCSꢁ
ligands, denoted as X, and having an S2PX donor set. The main ben-
efit of this work is that it provides different perspectives on mixed-
ligand nickel(II)–dithiocarbamato complexes in connection with
their solution properties, specifically it describes their behaviour
upon dissolving in various solvents. These findings may play a sig-
nificant role in a broader context of possible practical applications
of nickel dithiocarbamates.
2. Experimental
2.1. Materials
Chemicals and solvents used in this work were purchased from
Sigma–Aldrich Co. (N-benzylpiperazine, thiomorpholine, tripheny-
phosphine), Fluka Co. (CS2) and Lachema Co. (solvents).
[Ni(bpdtc)2], [Ni(tmdtc)2] and [NiX2(PPh3)2] were prepared as
formerly described elsewhere [5,7,12]; X = Clꢁ, Brꢁ, Iꢁ, NCSꢁ.
2.2. Syntheses of the complexes
⇑
The starting nickel(II) complexes [Ni(ndtc)2] (1 mmol) and
[NiX2(PPh3)2] (1 mmol) were pulverized and mixed together in
Corresponding author. Tel.: +420 585 634 352; fax: +420 585 634 954.
ˇ
E-mail address: zdenek.travnicek@upol.cz (Z. Trávnícek).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.11.041

R. Pastorek et al. / Polyhedron 69 (2014) 174–180
175
20 mL of CHCl3. The suspension was stirred until dissolved (ca.
2.3. Physical methods
45 min) and then 1 mg of activated charcoal was added. The mix-
ture was filtered off and diethyl ether (ca. 3 mL) was poured into
the filtrate and left to crystallize for two days (note: in the case that
crystals did not form after two days, another portion of diethyl
ether was added and the solution was left to crystallize). Micro-
crystals of [NiX(ndtc)(PPh3)] (1–8; Scheme 1) were filtered off
and washed with diethyl ether (3 ꢂ 5 mL) and dried at 40 °C under
an infrared lamp. Crystals suitable for single-crystal X-ray analysis
were obtained as follows: complex 1 was dissolved in CHCl3, the
solution was filtered and left to stand in a refrigerator, where dark
violet crystals formed after a few days.
[NiCl(bpdtc)(PPh3)] (1): Light violet crystals. Yield: 66%. Anal.
Calc. for C30H30N2ClNiPS2: C, 59.28; H, 4.97; N, 4.61; Cl, 5.83; Ni,
9.66. Found: C, 58.86; H, 5.01; N, 4.70; Cl, 6.25; Ni, 9.71%. kM
(MeNO2/MeCN; S cm2 molꢁ1): 2.2/14.0. UV–Vis (Me2CO/MeCN/
CHCl3 solution; ꢂ103 cmꢁ1): 19.5/19.6/19.4. emax (Me2CO/MeCN/
CHCl3 solution; Mꢁ1 cmꢁ1): 472.2/504.9/459.9.
Elemental analyses (C, H, N) were performed on a Flash 2000
CHNO-S Analyser (Thermo Scientific). Chlorine and bromine con-
tents were determined using the Schöniger method. The nickel
content was determined by chelatometric titration with murexide
as an indicator. The measurements of the room temperature mag-
netic susceptibilities were performed using the Faraday method
with a laboratory designed instrument and with a Sartorius 4434
MP-8 microbalance. Co[Hg(NCS)4] was used as a calibrant and
the correction for diamagnetism was performed using Pascal con-
stants [13]. The molar conductivity of the 10ꢁ3 M nitromethane
(MeNO2; 1–8) and acetonitrile (MeCN; 1, 5) solutions was mea-
sured by an LF 330/SET conductometer (WTW GmbH) at 25 °C.
Electronic absorption spectra (10ꢁ3 M solutions in acetone (Me2-
CO), MeCN, N,N0-dimethylformamide (DMF), dimethyl sulfoxide
(DMSO), chloroform (CHCl3) and MeNO2; the complexes were not
soluble in methanol (MeOH), ethanol (EtOH) and water up to the
10ꢁ3 M concentration) and diffuse-reflectance spectra were re-
corded on a Lambda 40 spectrometer (Perkin-Elmer) in the range
200–1000 nm. IR spectra (450–4000 cmꢁ1 region; KBr pellets)
were recorded on a Perkin-Elmer Spectrum one FT-IR spectrome-
ter. 31P NMR spectra of CDCl3 (1–8) and DMSO-d6 (1, 5) solutions
were measured at 300 K on a Varian 400 MHz NMR device and
the spectra were calibrated against the signals of 85% H3PO4, used
as an external standard. Mass spectra of solutions of 1, 4, 5 and 8 in
Me2CO, MeCN, MeOH, DMF, CHCl3, MeNO2, and a MeOH/H2O mix-
ture (1:1 v/v), and [Ni(ndtc)2] and [NiCl2(PPh3)2] in DMF were re-
corded on an LCQ Fleet Ion Mass Trap spectrometer (Thermo
Scientific Inc.) using the electro-spray ionization technique in the
positive mode (ESI+).
[NiBr(bpdtc)(PPh3)] (2): Dark violet crystals. Yield: 62%. Anal.
Calc. for C30H30N2BrNiPS2: C, 55.24; H, 4.64; N, 4.29; Br, 12.25;
Ni, 9.00. Found: C, 54.87; H, 4.60; N, 4.44; Br, 12.51; Ni, 9.11%.
kM (MeNO2; S cm2 molꢁ1): 2.4.
[NiI(bpdtc)(PPh3)] (3): Light violet crystals. Yield: 54%. Anal.
Calc. for C30H30N2INiPS2: C, 51.53; H, 4.32; N, 4.01; Ni, 8.39. Found:
C, 51.26; H, 4.50; N, 4.13; Ni, 8.18%. kM (MeNO2; S cm2 molꢁ1): 2.3.
[Ni(NCS)(bpdtc)(PPh3)] (4): Light red crystals. Yield: 57%. Anal.
Calc. for C31H30N3INiPS3: C, 59.06; H, 4.80; N, 6.67; Ni, 9.31. Found:
C, 58.78; H, 4.40; N, 6.62; Ni, 9.43%. kM (MeNO2; S cm2 molꢁ1): 2.6.
[NiCl(tmdtc)(PPh3)]ꢀ½CHCl3 (5): Dark violet crystals. Yield: 68%.
Anal. Calc. for C23H23NClNiPS3ꢀ½CHCl3: C, 47.48; H, 3.98; N, 2.36;
Cl, 14.91; Ni, 9.87. Found: C, 46.98; H, 3.93; N, 2.56; Cl, 14.43;
Ni, 10.08%. kM (MeNO2/MeCN; S cm2 molꢁ1): 3.3/20.5. UV–Vis
(Me2CO/MeCN/CHCl3 solution; ꢂ103 cmꢁ1): 19.4/19.5/19.4. emax
(Me2CO/MeCN/CHCl3 solution; Mꢁ1 cmꢁ1): 570.6/763.1/452.8.
[NiBr(tmdtc)(PPh3)]ꢀ½CHCl3 (6): Dark violet crystals. Yield: 63%.
Anal. Calc. for C23H23NBrNiPS3ꢀ½CHCl3: C, 44.18; H, 3.71; N, 2.19; X,
12.51; Ni, 9.19. Found: C, 44.01; H, 3.53; N, 2.25; X, 12.03; Ni,
9.47%. X = Br + Cl. kM (MeNO2; S cm2 molꢁ1): 3.2.
[NiI(tmdtc)(PPh3)]ꢀ½CHCl3 (7): Dark brown crystals. Yield: 55%.
Anal. Calc. for C23H23NINiPS3ꢀ½CHCl3: C, 41.15; H, 3.45; N, 2.04; Ni,
8.56. Found: C, 41.52; H, 3.13; N, 2.29; Ni, 8.89%. kM (MeNO2;
S cm2 molꢁ1): 3.6.
[Ni(NCS)(tmdtc)(PPh3)] (8): Light red crystals. Yield: 51%. Anal.
Calc. for C24H23N2NiPS4: C, 51.72; H, 4.16; N, 5.03; Ni, 10.53.
Found: C, 51.34; H, 3.72; N, 4.90; Ni, 10.37%. kM (MeNO2;
S cm2 molꢁ1): 2.9.
2.4. Crystal structure determinations
A series of attempts to re-crystallize selected representatives (1,
4, 5 and 8) from different solvents (Me2CO, MeCN, MeOH, CHCl3,
MeNO2) with the aim to obtain crystals suitable for single crystal
X-ray analysis was performed. We were successful in the case of
re-crystallization of complex 1 from CHCl3, which led to the forma-
tion of well-shaped dark violet single crystals of which one was
used for the diffraction experiment. On the other hand, slow cool-
ing of hot (80 °C) DMF or DMSO solutions of 1, 4, 5 and 8, as well as
slow evaporation of DMF solutions of 1, 4, 5 and 8 at room temper-
ature led to uniform crystallidne products, whose compositions
corresponded to the starting compounds [Ni(bpdtc)2] and
[Ni(tmdtc)2], as proven by elemental analysis, mass spectrometry
and X-ray analysis. The crystals obtained by slow evaporation of
a DMF solution of 1 and by cooling of a hot DMSO solution of 8
were selected as representatives of both groups of products (i.e.
[NiX(bpdtc)(PPh3)] (1–4) and [NiX(tmdtc)(PPh3)] (5–8)), differing
in the ndtc ligand.
The single-crystal X-ray analyses of selected crystals of
[NiCl(bpdtc)(PPh3)] (1), [Ni(bpdtc)2] and [Ni(tmdtc)2] were col-
lected on an XcaliburTM2 diffractometer (Oxford Diffraction Ltd.)
with a Sapphire2 CCD detector and with Mo K
a radiation (Mono-
chromator Enhance, Oxford Diffraction Ltd.). Data collection and
reduction were performed using the CRYSALIS software [14]. This
software was also used for data correction for absorption effects
(empirical absorption correction using spherical harmonics) imple-
mented in the SCALE3 ABSPACK scaling algorithm. The structures were
solved by direct methods (SHELXS-97) and refined on F2 using the
full-matrix least-squares procedure by SHELXL-97 [15]. Non-hydro-
gen atoms were refined anisotropically. Hydrogen atoms were
located in a difference map and refined by the riding model:
C–H = 0.95 (CH) and 0.99 (CH2) Å, and Uiso(H) = 1.2 Ueq(CH, CH2).
Atoms of one phenyl ring of a PPh3 molecule of 1 are disordered
Scheme 1. Structural formulas of the studied complexes.

176
R. Pastorek et al. / Polyhedron 69 (2014) 174–180
Table 1
Crystal data and structure refinement for [Ni(bpdtc)2], [Ni(tmdtc)2] and [NiCl(bpdtc)(PPh3)] (1).
[Ni(bpdtc)2]
[Ni(tmdtc)2]
[NiCl(bpdtc)(PPh3)] (1)
Empirical formula
Formula weight
T (K)
C
24H30N4S4Ni
C10H16N2S6Ni
415.32
120(2)
C30H30N2ClNiPS2
607.81
120(2)
561.47
120(2)
k (Å)
0.71073
monoclinic
P21/n
0.71073
monoclinic
P21/n
0.71073
Crystal system
Space group
Unit cell dimensions
a (Å)
b (Å)
c (Å)
triclinic
ꢀ
P1
12.9570(4)
6.5281(2)
31.1594(10)
90
4.4296(2)
20.8438(6)
8.4902(2)
90
9.9872(3)
10.8573(3)
13.2971(3)
95.342(2)
a
(°)
b (°)
96.210(3)
90
2620.2(2)
4
1.423
1.079
97.055(3)
90
777.97(4)
2
1.773
2.038
93.702(2)
93.677(2)
1429.04(6)
2
1.413
c
(°)
V (Å3)
Z
Dcalc (g cmꢁ3
)
Absorption coefficient (mmꢁ1
Crystal size (mm)
)
0.997
0.25 ꢂ 0.20 ꢂ 0.10
0.20 ꢂ 0.15 ꢂ 0.10
0.25 ꢂ 0.25 ꢂ 0.10
F(000)
1176
428
632
h range for data collection (°)
Index ranges (h,k,l)
3.16 6 h 6 25.00
ꢁ15 6 h 6 12
ꢁ7 6 k 6 7
ꢁ37 6 l 6 37
23547/4613 (0.0238)
4613/0/289
1.009
3.11 6 h 6 24.99
ꢁ5 6 h 6 4
ꢁ24 6 k 6 24
ꢁ10 6 l 6 10
7123/1365 (0.0256)
1365/0/88
1.084
3.08 6 h 6 25.00
ꢁ11 6 h 6 11
ꢁ12 6 k 6 11
ꢁ15 6 l 6 15
14135/5000 (0.0325)
5000/66/384
0.958
Reflections collected/unique (Rint
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
)
Final R indices [I > 2
r
(I)]
R1 = 0.0293
wR2 = 0.0824
R1 = 0.0627
wR2 = 0.0859
0.363, ꢁ0.195
R1 = 0.0221
wR2 = 0.0544
R1 = 0.0283
wR2 = 0.0554
0.363, ꢁ0.204
R1 = 0.0333
wR2 = 0.0694
R1 = 0.0511
wR2 = 0.0721
0.467, ꢁ0.550
R indices (all data)
Largest peak and hole (e Åꢁ3
)
over two positions with occupancy factors of 0.52, and 0.48. The
crystal data and structure refinements are given in Table 1. The
molecular graphics were drawn and additional structural calcula-
tions were interpreted with DIAMOND software [16].
phosphorus atom of the PPh3 molecule and one chloride anion, giv-
ing a ClPS2 donor set (Fig. 1, Table 3). One phenyl ring of the PPh3
molecule is distorted over two positions with occupancy factors of
0.520(5) and 0.480(5). The bond lengths around the metal centre,
given in Table 3, were compared with those of nine formerly re-
ported [NiCl(ndtc)(PPh3)] complexes [22–30] involving different
dithiocarbamate ligands. In the case of Ni–S (2.171–2.231 Å range,
average value based on a CSD search: 2.202 Å; Ni–S = 2.1724(7)
and 2.2181(6) Å for 1) and Ni–P (2.185–2.224 Å range, average va-
lue based on a CSD search: 2.202 Å; Ni–P = 2.2029(6) Å for 1), the
values of 1 fall into reported ranges. However, the Ni–Cl bond
length of 1 (2.1627(7) Å) was found to be shorter as compared with
previously reported analogous nickel(II) dithiocarbamato com-
plexes (2.174–2.195 Å range, average value based on a CSD search:
2.184 Å).
3. Results
3.1. General properties
The composition of the prepared complexes correlates with the
results of the elemental analyses (the differences between the
calculated and found contents were not higher than 0.50%). The
magnetochemical experiments proved the complexes to be
diamagnetic, which corresponds with a square-planar geometry
of the nickel(II) complexes. The molar conductivity values of 1–8
dissolved in MeNO2 were found to be in the range 2.2–3.6 S cm2 -
molꢁ1, which are characteristic values for non-electrolytes in the
The crystal structure of 1 (Fig. 2) is stabilised by a network of
non-covalent contacts of the C–Hꢀ ꢀ ꢀCl, C–Hꢀ ꢀ ꢀS, C–Hꢀ ꢀ ꢀ
p and
C–Hꢀ ꢀ ꢀC types, thus forming a 3D supramolecular architecture, in
which two adjacent molecules are centrosymmetrically connected
through the C4–Hꢀ ꢀ ꢀS2 interactions. Selected parameters of the
non-covalent contacts are as follows: C2–H2Bꢀ ꢀ ꢀC1 with
d(Dꢀ ꢀ ꢀA) = 3.718(4) Å; C4–H4Bꢀ ꢀ ꢀS2 with d(Dꢀ ꢀ ꢀA) = 3.897(2) Å;
C6–H6Aꢀ ꢀ ꢀCg with d(Dꢀ ꢀ ꢀA) = 3.552(2) Å; C23–H23Aꢀ ꢀ ꢀS2 with
solvent used [17]. The maxima of the
m
(Cꢀ ꢀ ꢀS) and (Cꢀ ꢀ ꢀN) vibra-
m
tions, characteristic for the dithiocarbamato moiety, were detected
in the IR spectra of all the complexes at 995–998 and 1507–
1531 cmꢁ1, respectively (Table 2) [18,19]. The IR spectra of 4 and
8 also contain the bands of the
m
(C–S) (maximum at 844 cmꢁ1
as(C„N) (maximum at 2090 cmꢁ1
for 4 and 839 cmꢁ1 for 8) and
m
d(Dꢀ ꢀ ꢀA) = 3.704(2) Å;
C32–H32Aꢀ ꢀ ꢀC10
with
d(Dꢀ ꢀ ꢀA) =
for 4 and 2098 cmꢁ1 for 8) vibrations, indirectly showing the coor-
dination of the NCSꢁ group to nickel(II) through the nitrogen atom
[20,21].
3.526(6) Å; C42–H42Aꢀ ꢀ ꢀCl1 with d(Dꢀ ꢀ ꢀA) = 3.473(2) Å. Detailed
information about the above discussed non-covalent contacts is gi-
ven in Table S1 in Appendix A, Supplementary data.
The molecular structures of both [Ni(bpdtc)2] and [Ni(tmdtc)2]
are centrosymmetric (Fig. S1 in Appendix A, Supplementary data).
[Ni(bpdtc)2] involves two halves of crystallographically indepen-
dent molecules within the unit cell, with a Niꢀ ꢀ ꢀNi separation of
6.4785(2) Å. The Ni(II) atoms are tetra-coordinated by four sulfur
atoms of two bpdtc ligands (Table 3). The determined Ni–S bond
lengths of [Ni(bpdtc)2] and [Ni(tmdtc)2] (Table 3) do not differ from
3.2. X-ray structure of [NiCl(bpdtc)(PPh3)] (1), [Ni(bpdtc)2] and
[Ni(tmdtc)2]
The complex [NiCl(bpdtc)(PPh3)] (1), with a distorted square-
planar geometry, consists of a central Ni(II) atom tetra-coordinated
by two sulfur atoms (a bidentate-coordinated bpdtc anion), one

R. Pastorek et al. / Polyhedron 69 (2014) 174–180
177
Table 2
Selected NMR, IR and electronic (diffuse-reflectance and solution absorption spectra of 10ꢁ3 M nitromethane (MeNO2), N,N0-dimethylformamide (DMF) and dimethyl sulfoxide
(DMSO) solutions) spectral data for 1–8.
a
Complex
31P NMR (ppm)
IR (cmꢁ1
)
Uv–Vis (ꢂ103 cmꢁ1
)
b
m
(Cꢀ ꢀ ꢀS)
m
(Cꢀ ꢀ ꢀN)
Diffuse-reflectance
MeNO2
DMFc
1
2
3
4
5
6
7
8
20.7
23.6
29.0
29.4
36.3
44.3
40.4
34.0
995m
995m
996m
996m
996m
997m
997m
998m
1521s
1520s
1524s
1531s
1528s
1518s
1507s
1518s
19.5, 28.3, 41.1
19.1, 27.9, 40.9
19.6 (443.2)
19.4 (387.9)
19.2 (370.7)
20.9 (795.2)
19.5 (620.7)
19.2 (481.8)
18.9 (286.3)
20.8 (884.1)
15.8, 21.2
15.7, 21.2
18.6, 29.8, 36.3, 44.9
20.9, 29.9, 40.7
19.7, 29.7, 41.7
19.0, 27.9, 40.2
18.4, 27.8, 43.6
20.3, 28.1, 42.6
15.7, 21.2sh
15.7, 21.3
15.8, 21.2sh
15.8, 21.1sh
15.8, 21.2sh
15.8, 21.2sh
a
b
c
m = middle intensity; s = strong intensity.
the values of molar absorption coefficients are in parentheses (Mꢁ1 cmꢁ1).
sh = shoulder.
Fig. 1. The molecular structure of [NiCl(bpdtc)(PPh3)] (1) with non-hydrogen atoms drawn as thermal ellipsoids at the 50% probability level. One phenyl ring of the PPh3
molecule, involving C30–C35, is distorted over two positions with occupancy factors of 0.520(5) and 0.480(5).
those deposited in CSD for 86 nickel(II) bis(dithiocarbamato) com-
plexes (2.147–2.227 Å range, average value of 2.200 Å). The crystal
structures of the complexes are stabilized by C–Hꢀ ꢀ ꢀNi, C–Hꢀ ꢀ ꢀS and
C–Hꢀ ꢀ ꢀC (for [Ni(bpdtc)2]; see Fig. S2 in Appendix A, Supplementary
data) and C–Hꢀ ꢀ ꢀS (for [Ni(tmdtc)2]; see Fig. S3 in Appendix A, Sup-
plementary data) non-covalent contacts, whose parameters are
listed in Tables S2 and S3 in Appendix A, Supplementary data.
compared with the mentioned starting compounds (Fig. 4). Similar
electronic spectra to those of diffuse-reflectance and MeNO2 and
DMF solution spectra of [Ni(bpdtc)2] and [Ni(tmdtc)2] and DMF
(or DMSO) solutions of 1 and 5, which involved two maxima at
15000–16100 and 22100–24400 cmꢁ1
, corresponding to the
1A1g?1A2g and 1A1g?1B1g transitions, were recently reported for
the nickel(II) bis(alkyldithiocarbamato) complex [Ni(ndtc)2] [34].
As for the second type of used starting compounds, i.e. [NiX2
(PPh3)2], two maxima can be found both in the solid state and
10ꢁ2 M DMF solution spectra, however, the spectra differ mutually
in the curve shapes and maxima positions (Fig. 4). This difference is
most probably connected with the change in composition and/or
stereochemistry due to the formation of differently solvated
[NiXA(solv)B] species (X = Clꢁ or NCSꢁ; solv = DMF, DMSO; with
varying ratios of A/B). For example, [NiCl(DMF)x]+ (x = 1–3) species
were detected in the mass spectra of 1 and 5 (see below).
3.3. UV–Vis spectroscopic study
The presence of bands at 18400–20900 cmꢁ1 (543–478 nm) in
the diffuse-reflectance spectra of 1–8, assignable to the 1A1g?1B1g
transition of the square-planar nickel(II) complexes [18,31,32],
together with diamagnetic properties, support the assumption of
the square-planar arrangement in the vicinity of the metal centre.
The maxima, which exceeded 28,000 cmꢁ1, may be connected with
intraligand charge-transfer (CT) transitions within the S2CN moiety
[18,33]. Regarding the above mentioned maxima at 18400–
20900 cmꢁ1, their positions are in good agreement with those
detected in Me2CO, MeCN and CHCl3 spectra of 1–8, but they differ
from those detected in DMF and DMSO solutions of the studied
nickel(II) complexes (Table 2, Figs. 3 and S4).
To better understand the different behaviour of the studied
complexes in DMF and DMSO, a comparison of the solution spectra
of complexes 1–8 in DMF and DMSO with the diffuse-reflectance
and MeNO2 and DMF solution spectra of the starting compounds
[Ni(bpdtc)2] (precursor of 1–4) and [Ni(tmdtc)2] (precursor of
5–8) was performed. The obtained results showed the same max-
ima positions in the DMF and DMSO solution spectra of 1–8 as
3.4. ESI mass spectrometry
ESI+ mass spectra of 1, 4, 5 and 8 in Me2CO, MeCN, MeOH, DMF,
CHCl3, MeNO2 and a MeOH/H2O mixture were recorded. All spectra
(except for the MeOH/H2O mixture) contained peaks corresponding
to [Ni(ndtc)(PPh3)]+ (m/z 571.2 for 1 and 4; m/z 498.2 for 5 and 8)
and [Ni(ndtc)(PPh3)2]+ (m/z 832.9 for 1 and 4; m/z 760.1 for 5 and
8) species. The Me2CO, MeCN and DMF spectra involved peaks
assignable to [Ni(solv)(ndtc)(PPh3)]+, where solv stands for the
molecule of the mentioned solvent [35]. The species
[Ni(solv)(ndtc)(PPh3)2]+ were detected only in MeCN solutions,
while the [Ni(ndtc)(PPh3)3]+ species (m/z 1170.0 for 1 and 4; m/z

178
R. Pastorek et al. / Polyhedron 69 (2014) 174–180
[Ni(solv)(ndtc)(PPh3)]+ and [Ni(ndtc)(PPh3)2]+ peaks significantly
decreased as compared with the mass spectra in other solvents,
and the strong peaks corresponding to [NiCl(DMF)x]+ (x = 1–3, m/z
165.9, 238.9 and 311.7) and the low-intense peaks assignable to
[Ni(bpdtc)(DMF)2]+ (m/z 454.8), [Ni(bpdtc)2]+ (m/z 560.1; which
may result from the in-source oxidation during the electrospray
ionization) and [(Ni(bpdtc)2Ni(bpdtc)]+ (m/z 868.9) species
appeared in the DMF solution mass spectra (Figs. 5, S5 and S8).
The mass spectra obtained in the MeOH/H2O mixture contained
Table 3
Selected bond lengths (Å) and angles (°) of two crystallographically independent
halves of [Ni(bpdtc)2] (symmetry code: i) -x, -y, -z), [Ni(tmdtc)2] (symmetry code: i) -
x, -y, -z) and [NiCl(bpdtc)(PPh3)] (1) determined by a single-crystal X-ray analysis.
Parameter
X-ray analysis
[NiCl(bpdtc)(PPh3)] (1) [Ni(bpdtc)2]a
[Ni(tmdtc)2]
Ni1–S1
Ni1–S2
Ni1–S1i
Ni1–S2i
2.1724(7)
2.2007(13)/
2.2013(13)
2.1967(13)/
2.1983(13)
2.2007(13)/
2.2012(13)
2.1968(13)/
2.1982(13)
2.1996(5)
2.2181(6)
2.2074(5)
2.1997(5)
2.2075(5)
–
–
Ni1–P1
2.2029(6)
–
–
Ni1–Cl1
S1–C1
S2–C1
2.1627(7)
1.729(2)
1.706(2)
1.309(3)
–
–
1.699(5)/1.740(5)
1.717(5)/1.731(5)
1.309(6)/1.309(6)
79.70(5)/79.78(5)
180.0/180.0
100.30(5)/100.22(5)
100.30(5)/100.22(5)
180.0/180.0
79.70(5)/79.78(5)
1.723(2)
1.717(2)
1.318(2)
79.08(2)
180.0
100.92(2)
100.92(2)
180.0
C1–N1
S1–Ni1–S2
S1–Ni1–S1i
S1–Ni1–S2i
S2–Ni1–S1i
S2–Ni1–S2i
S1i–Ni1–
S2i
78.60(2)
–
–
–
–
–
79.08(2)
S1–Ni1–P1
93.94(2)
–
–
–
–
–
–
–
–
–
–
S1–Ni1–Cl1 170.27(3)
S2–Ni1–P1 170.37(2)
S2–Ni1–Cl1 91.97(2)
P1–Ni1–
Cl1
95.15(2)
Ni1–S1–C1
Ni1–S2–C1
S1–C1–N1
S2–C1–N1
86.90(8)
86.00(8)
124.5(2)
127.4(2)
84.7(2)/85.5(2)
84.4(2)/85.8(2)
125.2(4)/125.0(4)
123.7(4)/126.2(4)
85.83(7)
85.72(6)
124.89(14)
125.82(14)
a
Values of two crystallographically independent halves of molecules within the
unit cell.
1022.0 for 5 and 8) were identified in MeNO2 (1 and 4) or MeCN (5
and 8) solutions (Fig. 5, S5–7). However, the situation was different
in the DMF solution because the intensities of the [Ni(ndtc)(PPh3)]+,
Fig. 3. The diffuse-reflectance (up) and electronic absorption spectra of 10ꢁ3
MeNO2 solutions (middle) and 10ꢁ3 M DMF solutions (down) of complexes 1–8.
M
Fig. 2. Part of the crystal structure of [NiCl(bpdtc)(PPh3)] (1) with the C2–H2Bꢀ ꢀ ꢀC1, C4–H4Bꢀ ꢀ ꢀS2, C6–H6Aꢀ ꢀ ꢀCg, C32–H32Aꢀ ꢀ ꢀC10 and C42–H42Aꢀ ꢀ ꢀCl1 non-covalent
contacts; the hydrogen atoms not involved in the depicted non-covalent contacts are omitted for clarity. Symmetry codes: (ii) ꢁx + 1, ꢁy, ꢁz + 1; (iii) ꢁx, ꢁy, ꢁz + 1; (iv)
ꢁx + 1, ꢁy, ꢁz + 2); (vi) x ꢁ 1, y, z ꢁ 1 and viii) x ꢁ 1, y, z.

R. Pastorek et al. / Polyhedron 69 (2014) 174–180
179
only the peaks corresponding to the [NiCl(H2O)x]+ species (x = 2–5)
and PPh3 (Figs. 5 and S5).
the respective ndtc anions. As for the X ligands within the struc-
tures of [NiX(ndtc)(PPh3)], where X = Clꢁ (1, 5), Brꢁ (2, 6), Iꢁ (3,
7) or NCSꢁ (4, 8), they deshield the phosphorus atom as well. As
a consequence of these facts, the chemical shifts differ not only
between the groups of complexes 1–4 and 5–8 (due to the ndtc
anion), but also within each of the discussed groups (due to the
X anion). A similar phenomenon was described in the literature
for the [NiX(ndtc)(PPh3)] type of compounds, where the mentioned
ligands showed a deshielding ability as follows: NCSꢁ > Clꢁ [25]
and Clꢁ > NCSꢁ > Brꢁ > Iꢁ [23,36].
In the case of the spectra measured in DMSO-d6 solutions of 1
and 5, the chemical shift of PPh3 in the 31P NMR spectra corre-
sponded to free non-coordinated PPh3 molecules (ꢁ6.8 ppm for
free PPh3; ꢁ6.7 ppm for complex 1 and ꢁ6.3 ppm for complex 5),
while no signal in the above-mentioned region typical for a coordi-
nated PPh3 molecule was detected.
3.5. 31P NMR spectroscopy
The signals of the coordinated PPh3 molecules of complexes 1–8
were detected at 20.7–44.3 ppm (Table 2) in the 31P NMR spectra
measured in CDCl3 solution. The differences in chemical shifts
between the [NiX(bpdtc)(PPh3)] (1–4; 20.7–29.4 ppm) and
[NiX(tmdtc)(PPh3)] (5–8; 34.0–44.3 ppm) complexes may be
caused by a different value of the back bonding interaction of both
4. Conclusion
This work reports the preparation and thorough characteriza-
tion of nickel(II) dithiocarbamates of the composition
[NiX(ndtc)(PPh3)] {ndtc stands for benzylpiperazine–dithiocarba-
mate (bpdtc; 1–4) and thiomorpholine–dithiocarbamate (tmdtc;
5–8); X = Clꢁ, Brꢁ, Iꢁ, NCSꢁ}. The X-ray structure of complex 1
proved the distorted square-planar geometry of the complex. In
an effort to elucidate the solution properties of the complexes,
the representatives 1, 4, 5 and 8 were studied to determine their
behaviour in different solvents in more detail. The complexes were
found to be stable in Me2CO, MeCN, MeOH, CHCl3 and MeNO2.
However, their stability was considerably lowered in DMF and
DMSO, since the studied complexes decomposed to [Ni(ndtc)2]
and other undefined solvated Ni(II) species during their dissolution
in these solvents. This work provides important evidence that the
species in solution can significantly differ from those in solid state
Fig. 4. Comparison of the electronic spectra of [NiCl(bpdtc)(PPh3)] (1; red lines),
[Ni(bpdtc)2] (green lines) and [NiCl2(PPh3)2] (black lines) as recorded in the solid
state (solid lines) and as DMF solutions (dashed lines), showing the similarity or
differences in the stereochemistry of the studied complexes. (Color online.)
Fig. 5. ESI+ mass spectra of chloroform (CHCl3, black line), nitromethane (MeNO2, red line), methanol (MeOH, blue line), acetone (Me2CO, green line), acetonitrile (MeCN,
magenta line), N,N0-dimethylformamide (DMF, light blue line) and methanol/water (1:1 v/v, MeOH/H2O, dark yellow line) solutions of 1 together with a description of the
species corresponding to the most important peaks (L = bpdtc). (Color online.)

180
R. Pastorek et al. / Polyhedron 69 (2014) 174–180
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The tables of the parameters of non-covalent contacts of
[NiCl(bpdtc)(PPh3)] (1; Table S1), [Ni(bpdtc)2] (Table S2) and
[Ni(tmdtc)2] (Table S3), molecular structures of [Ni(bpdtc)2] and
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